The infrared radiation temperature(IRT)variation concerning stress and crack evolution of rocks is a critical focus in rock mechanics domain and engineering disaster warning.In this paper,a methodology to extract the ...The infrared radiation temperature(IRT)variation concerning stress and crack evolution of rocks is a critical focus in rock mechanics domain and engineering disaster warning.In this paper,a methodology to extract the key IRT features related to stress and crack evolution of loaded rocks is proposed.Specifically,the wavelet denoising and reconstruction in thermal image sequence(WDRTIS)method is employed to eliminate temporal noise in thermal image sequences.Subsequently,the adaptive partition temperature drift correction(APTDC)method is introduced to alleviate temperature drift.On this basis,the spatial noise correction method based on threshold segmentation and adaptive median filtering(OTSU-AMF)is proposed to extract the key IRT features associated with microcracks of loaded rocks.Following temperature drift correction,IRT provides an estimation of the thermoelastic factor in rocks,typically around 5.29×10^(-5) MPa^(-1) for sandstones.Results reveal that the high-temperature concentrated region in cumulative thermal images of crack evolution(TICE)can elucidate the spatiotemporal evolution of localized damage.Additionally,heat dissipation of crack evolution(HDCE)acquired from TICE quantifies the progressive failure process of rocks.The proposed methodology enhances the reliability of IRT monitoring results and provides an innovative approach for conducting research in rock mechanics and monitoring engineering disasters.展开更多
The deformation in sedimentary rock induced by train loads has potential threat to the safe operation of tunnels. This study investigated the influence of stratification structure on the infrared radiation and tempora...The deformation in sedimentary rock induced by train loads has potential threat to the safe operation of tunnels. This study investigated the influence of stratification structure on the infrared radiation and temporal damage mechanism of hard siltstone. The uniaxial compression tests, coupled with acoustic emission(AE) and infrared radiation temperature(IRT) were conducted on siltstones with different stratification effects. The results revealed that the stratigraphic structure significantly affects the stress-strain response and strength degradation characteristics. The mechanical parameters exhibit anisotropy characteristics, and the stratification effect exhibits a negative correlation with the cracking stress and peak stress. The failure modes caused by the stratification effect show remarkable anisotropic features, including splitting failure(Ⅰ: 0°-22.50°, Ⅱ: 90°), composite failure(45°), and shearing failure(67.50°). The AE temporal sequences demonstrate a stepwise response characteristic to the loading stress level. The AE intensity indicates that the stress sensitivity of shearing failure and composite failure is generally greater than that of splitting failure. The IRT field has spatiotemporal migration and progressive dissimilation with stress loading and its dissimilation degree increases under higher stress levels. The stronger the stratification effect, the greater the dissimilation degree of the IRT field. The abnormal characteristic points of average infrared radiation temperature(AIRT) variance at local stress drop and peak stress can be used as early and late precursors to identify fracture instability. Theoretical analysis shows that the competitive relationship between compaction strengthening and fracturing damage intensifies the dissimilation of the infrared thermal field for an increasing stress level. The present study provides a theoretical reference for disaster warnings in hard sedimentary rock mass.展开更多
Ni^3＋ and Cr^3＋ doped Fe-Mn-Co-Cu-O spinels have been prepared by solid phase sintering. The valence states and distribution of transition ions in the spinel crystals are inferred by the consideration of thermodynam...Ni^3＋ and Cr^3＋ doped Fe-Mn-Co-Cu-O spinels have been prepared by solid phase sintering. The valence states and distribution of transition ions in the spinel crystals are inferred by the consideration of thermodynamic principle and crystalline field theory. The mierostructure and performance of those are studied by X-ray diffraction （XRD）, Fourier transform infrared （FT-IR）, and IRE-2 infrared radiant instrument. Ni3＋ and Cr3＋ occupy the vacancies or substitute the other ions in the spinel structures and form diverse spinel structures, which exhibit infrared integral emissivities of 0.93 in the whole band, and 0. 94 in the band within 14-25μm too. The content of Fe2O3 and MnO2 in the spinel crystals changes, maybe it induces infrared radiativity of spinels differently.展开更多
According to the practical conditions of coal roadway in Changcun Coal Mine of Lu＇an Mining Group, the deformation of rock surrounding roadway was experimentally studied by means of thermal infrared （TIP,） imaging ...According to the practical conditions of coal roadway in Changcun Coal Mine of Lu＇an Mining Group, the deformation of rock surrounding roadway was experimentally studied by means of thermal infrared （TIP,） imaging system in the process of confined compressions. It is found that the model surface TIR temperature （TIRT） changes with the increase of load. Furthermore, TIRT changes non-synchronously in different ranges such as the roof, floor, wall, corners and bolted ranges. The TIRT is higher in the location of stress concentration and bolted ranges than that in the location of stress relaxation and broken ranges. The interaction ranges of bolt and rock are determined preliminarily according to the corresponding relationship of TIRT fields and the strain fields of the surrounding rock. The new method of TIR image processing has been proved to be effective for the study of bolt support and observation of roadway stability under mine pressure.展开更多
Based on the thermodynamics theory and physical micro-properties of solid materials subjected to external loading at room temperature,a formula of calculating temperature difference of infrared radiation in terms of t...Based on the thermodynamics theory and physical micro-properties of solid materials subjected to external loading at room temperature,a formula of calculating temperature difference of infrared radiation in terms of the sum of three principal strains was deduced to quantitatively investigate the infrared radiation characteristics in test. Two typical specimens,the three-point bending beam and the disc pressed in diameter,were tested and their principal strains were calculated by finite element method in order to obtain the temperature differences of infrared radiation. Numerical results are in a good agreement with test results,which verifies the validity of the formula of calculating temperature differences of infrared radiation and the model of quantitatively describing the infrared radiation characteristics of solid materials,and reveals the corresponding inner physical mechanism.展开更多
Previous studies show that infrared radiation temperature(IRT)abnormalities are always accompanied by the crack development in rocks under external loads.In this context,experiments were conducted on preflawed sandsto...Previous studies show that infrared radiation temperature(IRT)abnormalities are always accompanied by the crack development in rocks under external loads.In this context,experiments were conducted on preflawed sandstone to investigate the infrared radiation characteristics during failure process.Two indicators were defined herein,i.e.coefficient of variation of IRT(CVIRT)and skewness of IRT(SIRT).The regression analysis shows that the IRT probability distributions during loading process fit the Gaussian model.The variations in the CVIRT are characterized by four stages:primary stage,steady stage,accelerating stage and post-peak stage.Besides,the variations in the SIRT are divided into three stages:primary stage,steady stage and failure and post-peak stage.The precursor point for preflawed rock failure is identified based on the CVIRTetime curve,with average precursor point of 83%of the peak stress.Compared with other IRT indicators,the proposed two IRT indicators have higher sensitivity to IRT abnormalities during failure process.Furthermore,the connection between the IRT indicators and the rock fracturing was investigated to interpret the IRT indicator abnormalities.Based on the Verhulst inverse function,a new quantitative model was presented to describe the primary stage,steady stage and accelerating stage of the CVIRTetime curve.The results obtained in this study can provide early-warning information for rock failure prediction.展开更多
In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional fro...In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional frost heave test system of infrared radiation technology, instead of a traditional thermistor method. Temperatures of the freezing fringe and segregated ice were measured in a non-contact mode. The results show that accurate and precise temperatures of ice segregation can be obtained by infrared thermal imaging systems. A self-developed inversion program inverted the temperature field of frozen soils. Based on our analysis of temperature variation in segregated ice and our study of the relationship between temperature and rate of ice segregation in cooling and warming processes during intermittent freezing, the mechanism of decreasing frost heave of frozen soils by controlling the growth of final lenses with an intermittent freezing mode, can be explained properly.展开更多
Zn^2＋ - or Ti^4＋ -substituted cordierites with the nominal compositions of Mg1 .6 Zn0.4 Al4 Si5 O18 and Mg1.8 Ti0.2 Al4.4 Si4.6 O18 respectively, were prepared by a conventional solid state reaction method. The stru...Zn^2＋ - or Ti^4＋ -substituted cordierites with the nominal compositions of Mg1 .6 Zn0.4 Al4 Si5 O18 and Mg1.8 Ti0.2 Al4.4 Si4.6 O18 respectively, were prepared by a conventional solid state reaction method. The structure of the substituted eordierites was characterized by X- ray diffraction （ XRD ）, infrared （ 1R ） spectroscopy and 29 Si magic angle spinning （ MAS ） nuclear magnetic resonance （ NMR ）. The infoared radiation properties were investigated in the bands within 2.5-25μm. Compared with the na-substituted cordierite composition （ Mg2 Al4 Si5 O18 ）, Zn^2＋ - or Ti^4＋ -substituted cordierites show superior infrared properties. XRD and IR results confirm the formation of hexagonal a-eordierite as the main eo＇stal phase for the substituted cordierites. 29 Si MAS NMR result indicates that Zn^2＋ or Ti^4＋ Substitutions for partial Mg^2＋ of a-eordierite promoted the ordering of the distribution oral and Si atoms in T1 （ tetrahedra connecting six-raembered rings together with [ MgO6] octahedra ） and T2 （ tetraheda forming six-reentered rings） tetrahedral sites. This resulted in a lattice deformation and increased the anharmonicity of polarization vibration, which is responsible for the improvement of infrared radiation properties of the substituted eordierites.展开更多
An experimental study on infrared radiation from the hot jet by means of model test is presented. The infrared detection system of the universal infrared instruments. the testing method and experimental results of inf...An experimental study on infrared radiation from the hot jet by means of model test is presented. The infrared detection system of the universal infrared instruments. the testing method and experimental results of infrared radiation from the hot jet are introduced. The space distribution of infaed radiant energy. the spectrum of infrared radiation from the hot jet. the distribution of the radiant energy of the hot jet against the wavebands and the characteristic difference of the hot jet radiaton between the 2-D jet tube and the circular jet tube are obtained. It is indicated that the testing system and the method are valid and the results are in accord with the theoretical analysis.展开更多
Co1-xZnxFe2O4 ferrites were prepared by solid state reaction. The microstructure and performance were studied by X-ray diffraction, X-ray absorption fine-structure analysis and IRE-2 infrared radiant test. It is found...Co1-xZnxFe2O4 ferrites were prepared by solid state reaction. The microstructure and performance were studied by X-ray diffraction, X-ray absorption fine-structure analysis and IRE-2 infrared radiant test. It is found that infrared radiance show a nonlinear change with x, exhibiting the infrared radiance of this material improved and the average radiance in the 8-14 μm waveband reached 0.91. The Co^3＋ and Zn^2＋ ions are found to occupy both tetrahedral and octahedral sites, and correspondingly, the fraction of Fe^3＋ ions in B-site decreases nonlinearly in ferrites. The lattice parameters are found to concern with Zn^2＋, and the activation energy deduces from crystal strain and crystal vibrate increases with content Zn^2＋. The redistribution of the Co^3＋ and Zn^2＋ ions between tetrahedral and octahedral sites is related to the providing a selective tetrahedral and octahedral sites infrared radiance of Co1-xZnxFe2O4 ceramics with increasing x.展开更多
Nowadays,it is a great challenge to reduce energy consumption and exhaust emission for human activities,in particular,high temperature industries.Among many efforts made to realize energy savings for high temperature ...Nowadays,it is a great challenge to reduce energy consumption and exhaust emission for human activities,in particular,high temperature industries.Among many efforts made to realize energy savings for high temperature furnaces and kilns,the use of high emissivity materials is considered to be an effective route to increase their thermal efficiency by enhancing heat transfer.Most materials with high refractoriness and superior chemical stability have weak infrared absorption and radiation properties;however,their emissivity in infrared regions（1 —25 μm） could be effectively increased by ion doping.This is attributed to three main mechanisms：1） distortion of the crystal lattice;2） increase of free carrier absorption; 3） formation of impurity energy level.In this paper,the development and advancement of various material systems with high emissivity including non-oxides and oxide based ceramics were reviewed.It is also suggested that the establishment of evaluation models or instruments for energy savings would be beneficial to design and application of high emissivity materials in various high-temperature environment.Furthermore,more efforts should be made on durability of high emissivity materials at high service temperatures and on the standardization of testing methods for emissivity.展开更多
Hypersonic vehicles emit strong infrared radiation from their high-temperature exhaust plume and body, which is critical for infrared early warning, tracking, and guidance. In this work, a comprehensive analysis is co...Hypersonic vehicles emit strong infrared radiation from their high-temperature exhaust plume and body, which is critical for infrared early warning, tracking, and guidance. In this work, a comprehensive analysis is conducted on the factors involved in air dissociation reaction within the shock layer of hypersonic missile heads, as well as the multi-component afterburning effect of the exhaust plume. A novel Reverse Monte Carlo Method(RMCM) is proposed for infrared radiation calculation, which utilizes two-dimensional Low-Discrepancy Sequences(LDS) to improve computational accuracy. The numerical calculations for a dagger-type missile show that afterburning reactions increase the temperature on the centerline of the outlet exhaust plume by about 1000 K. The total infrared radiation intensity of the missile is the highest in the 1–3 μm band, with the hightemperature wall of the nozzle being the primary source of solid radiation, and gas radiation primarily coming from H_(2)O. The radiation intensity of the missile exhaust plume in the 3–5 μm band is the highest, with radiation sources primarily coming from CO_(2), CO, and HCl. Afterburning reactions of the exhaust plume increase the total infrared radiation intensity of the missile by about 0.7times. These results can provide reference for the detection and guidance of hypersonic missiles.展开更多
The temperature distributions on the helicopter airframe and in the exhaust plume are affected seriously by the engine exhaust system, rotor downwash and solar irradiance. To precisely simulate temperature distributio...The temperature distributions on the helicopter airframe and in the exhaust plume are affected seriously by the engine exhaust system, rotor downwash and solar irradiance. To precisely simulate temperature distribution on the helicopter airframe and in the exhaust plume, the effects of rotor downwash and solar irradiance are considered in three-dimensional flow and heat transfer calculation under helicopter hovering. Based on the temperature distribution, a forward-backward ray tracing method is used to calculate the helicopter infrared （IR） radiation intensity. A numerical study is conducted on a fictitious helicopter model with an integrated exhaust system-tail airframe configuration, and the thermal and infrared radiation characteristics are analyzed.展开更多
One of the most important problems of stealth technology is to evaluate the infrared radiation （IR） level received by IR sensors from fighters to be detected. This article presents a synthetic method for calculating...One of the most important problems of stealth technology is to evaluate the infrared radiation （IR） level received by IR sensors from fighters to be detected. This article presents a synthetic method for calculating the IR emitted from aircraftskin. By reck- oning the aerodynamic heating and hot engine casing to be the main heat sources of the exposed aircraft-skin, a numerical model of skin temperature distribution is established through computational fluid dynamics （CFD） technique. Based on it, an infrared signature model for solving the complex geometry and structure of a fighter is proposed with the reverse Monte Carlo （RMC） method. Finally, by way of determining the IR intensity from aircraft-skin, the aircraft components that emit the most IR can be identified; and the cooling effects of the main aircraft components on IR intensity are investigated. It is found that reduction by 10 K in the skin temperature of head, vertical stabilizers and wings could lead to decline of more than 8% of the IR intensity on the aircraft-skin in front view while at the broadside of the aircraft, the drops in IR intensity could attain under 8%. The results provide useful reference in designing stealthy aircraft.展开更多
The infrared radiation signature of the plume from solid propellants with different energy characteristics is not the same. Three kinds of double-base propellants of different energy characteristics are chosen to meas...The infrared radiation signature of the plume from solid propellants with different energy characteristics is not the same. Three kinds of double-base propellants of different energy characteristics are chosen to measure the infrared spectral radiance from 1000 cm 1 to 4500 cm 1 of their plumes. The radiative spectrum is obtained in the tests. The experimental results indicate that the infrared radiation of the plume is determined by the energy characteristics of the propellant. The radiative transfer calculation models of the exhaust plume for the solid propellants are established. By including the chemical reaction source term and the radiation source term into the energy equation, the plume field and the radiative transfer are solved in a coupled way. The calculated results are consistent with the experimental data, so the reliability of the models is confirmed. The temperature distribution and the extent of the afterburning of the plume are distinct for the propellants of different energy characteristics, therefore the plume radiation varies for different propellants. The temperature of the fluid cell in the plume will increase or decrease to some extent by the influence of the radiation term.展开更多
Hot air(HA)drying of banana has low drying efficiency and results in undesirable product quality.The objectives of this research were to investigate the feasibility of infrared(IR)heating to improve banana drying rate...Hot air(HA)drying of banana has low drying efficiency and results in undesirable product quality.The objectives of this research were to investigate the feasibility of infrared(IR)heating to improve banana drying rate,evaluate quality of the dried product,and establish models for predicting drying characteristics.Banana slices of 5 mm and 8 mm thickness were dried with IR and HA at product temperatures of 60℃,70℃ and 80℃.Banana drying characteristics and changes in residual polyphenol oxidase(PPO),Hydroxymethylfurfural(HMF),color,moisture content(MC)and water activity during the treatments were investigated.Results showed that significant moisture reduction and higher drying rates were achieved with IR drying compared to HA drying in the early stage.The drying data could be fitted to the Page model for accurate prediction of MC change for IR and HA drying with mean R2 of 0.983.It was noted that enzyme inactivation occurred more quickly with IR than with HA drying.A unique response of PPO under IR and HA drying was revealed.IR heating of banana inactivated PPO within the first 20 min of drying at 60℃,70℃ and 80℃,while PPO was first activated before inactivation at 60℃ and 70℃ drying with HA.The highest HMF content occurred in banana slices with 5 mm thickness dried with IR at a product temperature of 80℃.It is therefore recommendable to dry banana with IR at product temperature of 70℃ or below to preserve the product quality.These findings are new and provide more insight in the application of IR heating for drying banana for improved drying rate and product quality.展开更多
Boron for aluminum substitution in the cordierite structure has been examined by sol-gel preparation of different samples along the compositional junction Mg2Al4-xBxSi5O18 with x=0,0.5,1,1.5.By increasing the x value ...Boron for aluminum substitution in the cordierite structure has been examined by sol-gel preparation of different samples along the compositional junction Mg2Al4-xBxSi5O18 with x=0,0.5,1,1.5.By increasing the x value from 0 to 1.5 the crystallization behavior changed accordingly.Proper amount B2O3 doping can promote the sintering of amorphous cordierite gel,effectively restrain the precipitation of μ-cordierite and enhance the crystallization of α-cordierite.The substitution of B3＋ for Al3＋ in cordierite crystal structure can effectively improve the near-infrared spectral emissivity of this cordierite based glass-ceramics.展开更多
This study seeks to determine the similarities in plume radiation between reduced and full-scale solid rocket models in ground test conditions through investigation of flow and radiation for a series of scale ratios r...This study seeks to determine the similarities in plume radiation between reduced and full-scale solid rocket models in ground test conditions through investigation of flow and radiation for a series of scale ratios ranging from 0.1 to 1. The radiative transfer equation (RTE) considering gas and particle radiation in a non-uniform plume has been adopted and solved by the finite volume method (FVM) to compute the three dimensional, spectral and directional radiation of a plume in the infrared waveband 2-6 mu m. Conditions at wavelengths 2.7 mu m and 4.3 mu m are discussed in detail, and ratios of plume radiation for reduced-scale through full-scale models are examined. This work shows that, with increasing scale ratio of a computed rocket motor, area of the high-temperature core increases as a 2 power function of the scale ratio, and the radiation intensity of the plume increases with 2-2.5 power of the scale ratio. The infrared radiation of plume gases shows a strong spectral dependency, while that of Al2O3 particles shows spectral continuity of gray media. Spectral radiation intensity of a computed solid rocket plume's high temperature core increases significantly in peak radiation spectra of plume gases CO and CO2 center dot Al2O3 particles are the major radiation component in a rocket plume. There is good similarity between contours of plume spectral radiance from different scale models of computed rockets, and there are two peak spectra of radiation intensity at wavebands 2.7-3.0 lm and 4.2-4.6 lm. Directed radiation intensity of the entire plume volume will rise with increasing elevation angle. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.展开更多
A multi-scale narrow band correlated-k distribution（MSNBCK） model is developed to simulate infrared radiation（IR） from an exhaust system of a typical aircraft engine.In this model,an approximate approach instead o...A multi-scale narrow band correlated-k distribution（MSNBCK） model is developed to simulate infrared radiation（IR） from an exhaust system of a typical aircraft engine.In this model,an approximate approach instead of statistically uncorrelated assumption is used to treat overlapping bands in gas mixture.It significantly reduces the requirement for computing power through converting the exponential increase of computing power consumption with the increase of participating gas species to linear increase.Besides,MSNBCK model has a great advantage compared with conventional methods which can estimate each species＇ contribution to the total gas mixture radiation intensity.Line by line（LBL） results,experimental data and other results in the references are used to evaluate this new model,which demonstrates its advantage in terms of accuracy and computing efficiency.By coupling this model and finite volume method（FVM） into radiative transfer equation（RTE）,a comparative study is conducted to simulate IR signature from the exhaust system.The results indicate that wall＇s IR emission should be considered in both 3-5 μm and8-14 μm bands while gases＇ IR emission plays an important role only in 3-5 μm band.For plume IR radiation,carbon dioxide＇s emission is much more significant than that of water vapor in both3-5μm and 8-14 μm bands.Especially in 3-5 μm band,the water vapor＇s IR signal can even be neglected compared with that of carbon dioxide.展开更多
To address deeper understandings about the aero-thermal performance of an integrating infrared suppressor under more realistic situations,a numerical investigation is motivated in the current study,concerning the effe...To address deeper understandings about the aero-thermal performance of an integrating infrared suppressor under more realistic situations,a numerical investigation is motivated in the current study,concerning the effects of forward-flight speed on exhaust plume flow and infrared radiation of the Infrared Suppressor-integrating(IRS-integrating)helicopter,wherein the forward-flight speed is changed from 0 m/s(hover state)to 100 m/s,while both the engine exhaust parameters and the main-rotor operation parameters remains unchanged during different forward-flight velocities.The results show that the interaction between forward-flight flow and downwash flow alters the exhaust plume development and the internal flow inside the IRS-integrating rear fuselage more complicatedly,tightly dependent on the forward-flight speed.Of particular concern is the situation where the forward-flight flow has nearly the same level as the downwash flow,the hot mixing flow could possibly interacts with the helicopter rear fuselage to play a local heating effect.With the increase of forward-flight speed,the ejection coefficient is generally increased and the average exhaust temperature of mixing flow is decreased,leading to a reduction of the infrared radiation intensity of exhaust plume in 3–5 lm band.However,the influence of forward-flight speed on the overall infrared radiation intensity of IRS-integrating helicopter is conjectured not monotonous due to the complicated interaction between forward-flight flow and downwash flow.Under high-speed forward-flight states,the overall infrared radiation intensity of the IRS-integrating helicopter in 3–5 lm band is reduced with the increase of forward-flight speed.With respect to 3–5 lm band,the forward-flight speed has little effect on the infrared radiation in 8–14 lm band.展开更多
基金supported by the National Natural Science Foundation of China(No.51874280)the Fundamental Research Funds for the Central Universities(No.2021ZDPY0211)+2 种基金the Graduate Innovation Program of China University of Mining and Technology(No.2023WLKXJ046)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX23_2811)the Project of Liaoning Provincial Department of Education(No.JYTMS20231458).
文摘The infrared radiation temperature(IRT)variation concerning stress and crack evolution of rocks is a critical focus in rock mechanics domain and engineering disaster warning.In this paper,a methodology to extract the key IRT features related to stress and crack evolution of loaded rocks is proposed.Specifically,the wavelet denoising and reconstruction in thermal image sequence(WDRTIS)method is employed to eliminate temporal noise in thermal image sequences.Subsequently,the adaptive partition temperature drift correction(APTDC)method is introduced to alleviate temperature drift.On this basis,the spatial noise correction method based on threshold segmentation and adaptive median filtering(OTSU-AMF)is proposed to extract the key IRT features associated with microcracks of loaded rocks.Following temperature drift correction,IRT provides an estimation of the thermoelastic factor in rocks,typically around 5.29×10^(-5) MPa^(-1) for sandstones.Results reveal that the high-temperature concentrated region in cumulative thermal images of crack evolution(TICE)can elucidate the spatiotemporal evolution of localized damage.Additionally,heat dissipation of crack evolution(HDCE)acquired from TICE quantifies the progressive failure process of rocks.The proposed methodology enhances the reliability of IRT monitoring results and provides an innovative approach for conducting research in rock mechanics and monitoring engineering disasters.
基金National Natural Science Foundation of China(No.52178393)2023 High-level Talent Research Project from Yancheng Institute of Technology(No.xjr2023019)+1 种基金Open Fund Project of Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering(Grant No.YT202302)Science and Technology Innovation Team of Shaanxi Innovation Capability Support Plan(No.2020TD005).
文摘The deformation in sedimentary rock induced by train loads has potential threat to the safe operation of tunnels. This study investigated the influence of stratification structure on the infrared radiation and temporal damage mechanism of hard siltstone. The uniaxial compression tests, coupled with acoustic emission(AE) and infrared radiation temperature(IRT) were conducted on siltstones with different stratification effects. The results revealed that the stratigraphic structure significantly affects the stress-strain response and strength degradation characteristics. The mechanical parameters exhibit anisotropy characteristics, and the stratification effect exhibits a negative correlation with the cracking stress and peak stress. The failure modes caused by the stratification effect show remarkable anisotropic features, including splitting failure(Ⅰ: 0°-22.50°, Ⅱ: 90°), composite failure(45°), and shearing failure(67.50°). The AE temporal sequences demonstrate a stepwise response characteristic to the loading stress level. The AE intensity indicates that the stress sensitivity of shearing failure and composite failure is generally greater than that of splitting failure. The IRT field has spatiotemporal migration and progressive dissimilation with stress loading and its dissimilation degree increases under higher stress levels. The stronger the stratification effect, the greater the dissimilation degree of the IRT field. The abnormal characteristic points of average infrared radiation temperature(AIRT) variance at local stress drop and peak stress can be used as early and late precursors to identify fracture instability. Theoretical analysis shows that the competitive relationship between compaction strengthening and fracturing damage intensifies the dissimilation of the infrared thermal field for an increasing stress level. The present study provides a theoretical reference for disaster warnings in hard sedimentary rock mass.
文摘Ni^3＋ and Cr^3＋ doped Fe-Mn-Co-Cu-O spinels have been prepared by solid phase sintering. The valence states and distribution of transition ions in the spinel crystals are inferred by the consideration of thermodynamic principle and crystalline field theory. The mierostructure and performance of those are studied by X-ray diffraction （XRD）, Fourier transform infrared （FT-IR）, and IRE-2 infrared radiant instrument. Ni3＋ and Cr3＋ occupy the vacancies or substitute the other ions in the spinel structures and form diverse spinel structures, which exhibit infrared integral emissivities of 0.93 in the whole band, and 0. 94 in the band within 14-25μm too. The content of Fe2O3 and MnO2 in the spinel crystals changes, maybe it induces infrared radiativity of spinels differently.
基金Projects 50374069 supported by National Natural Science Foundation of China and 2002CB412701 supported by 973 of China
文摘According to the practical conditions of coal roadway in Changcun Coal Mine of Lu＇an Mining Group, the deformation of rock surrounding roadway was experimentally studied by means of thermal infrared （TIP,） imaging system in the process of confined compressions. It is found that the model surface TIR temperature （TIRT） changes with the increase of load. Furthermore, TIRT changes non-synchronously in different ranges such as the roof, floor, wall, corners and bolted ranges. The TIRT is higher in the location of stress concentration and bolted ranges than that in the location of stress relaxation and broken ranges. The interaction ranges of bolt and rock are determined preliminarily according to the corresponding relationship of TIRT fields and the strain fields of the surrounding rock. The new method of TIR image processing has been proved to be effective for the study of bolt support and observation of roadway stability under mine pressure.
基金Projects (10775018, 10702010, 50374073) supported by the National Natural Science Foundation of ChinaProject(2002CB412701) supported by the National Basic Research Program of China
文摘Based on the thermodynamics theory and physical micro-properties of solid materials subjected to external loading at room temperature,a formula of calculating temperature difference of infrared radiation in terms of the sum of three principal strains was deduced to quantitatively investigate the infrared radiation characteristics in test. Two typical specimens,the three-point bending beam and the disc pressed in diameter,were tested and their principal strains were calculated by finite element method in order to obtain the temperature differences of infrared radiation. Numerical results are in a good agreement with test results,which verifies the validity of the formula of calculating temperature differences of infrared radiation and the model of quantitatively describing the infrared radiation characteristics of solid materials,and reveals the corresponding inner physical mechanism.
基金The research was funded by the National Natural Science Foundation of China(Grant No.11902128)the Applied Basic Research Foundation of Yunnan Province(Grant Nos.2019FI012 and 2018FB093)。
文摘Previous studies show that infrared radiation temperature(IRT)abnormalities are always accompanied by the crack development in rocks under external loads.In this context,experiments were conducted on preflawed sandstone to investigate the infrared radiation characteristics during failure process.Two indicators were defined herein,i.e.coefficient of variation of IRT(CVIRT)and skewness of IRT(SIRT).The regression analysis shows that the IRT probability distributions during loading process fit the Gaussian model.The variations in the CVIRT are characterized by four stages:primary stage,steady stage,accelerating stage and post-peak stage.Besides,the variations in the SIRT are divided into three stages:primary stage,steady stage and failure and post-peak stage.The precursor point for preflawed rock failure is identified based on the CVIRTetime curve,with average precursor point of 83%of the peak stress.Compared with other IRT indicators,the proposed two IRT indicators have higher sensitivity to IRT abnormalities during failure process.Furthermore,the connection between the IRT indicators and the rock fracturing was investigated to interpret the IRT indicator abnormalities.Based on the Verhulst inverse function,a new quantitative model was presented to describe the primary stage,steady stage and accelerating stage of the CVIRTetime curve.The results obtained in this study can provide early-warning information for rock failure prediction.
基金supported by the Key Project of the National Natural Science Foundation of China (No. 50534040)the Project of the National Natural Science Foundation of China (No. 40471021)
文摘In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional frost heave test system of infrared radiation technology, instead of a traditional thermistor method. Temperatures of the freezing fringe and segregated ice were measured in a non-contact mode. The results show that accurate and precise temperatures of ice segregation can be obtained by infrared thermal imaging systems. A self-developed inversion program inverted the temperature field of frozen soils. Based on our analysis of temperature variation in segregated ice and our study of the relationship between temperature and rate of ice segregation in cooling and warming processes during intermittent freezing, the mechanism of decreasing frost heave of frozen soils by controlling the growth of final lenses with an intermittent freezing mode, can be explained properly.
基金Funded by the National Natural Science Foundation of China(No.50342014 ) and Key Technology Project of Wuhan City(20026002093)
文摘Zn^2＋ - or Ti^4＋ -substituted cordierites with the nominal compositions of Mg1 .6 Zn0.4 Al4 Si5 O18 and Mg1.8 Ti0.2 Al4.4 Si4.6 O18 respectively, were prepared by a conventional solid state reaction method. The structure of the substituted eordierites was characterized by X- ray diffraction （ XRD ）, infrared （ 1R ） spectroscopy and 29 Si magic angle spinning （ MAS ） nuclear magnetic resonance （ NMR ）. The infoared radiation properties were investigated in the bands within 2.5-25μm. Compared with the na-substituted cordierite composition （ Mg2 Al4 Si5 O18 ）, Zn^2＋ - or Ti^4＋ -substituted cordierites show superior infrared properties. XRD and IR results confirm the formation of hexagonal a-eordierite as the main eo＇stal phase for the substituted cordierites. 29 Si MAS NMR result indicates that Zn^2＋ or Ti^4＋ Substitutions for partial Mg^2＋ of a-eordierite promoted the ordering of the distribution oral and Si atoms in T1 （ tetrahedra connecting six-raembered rings together with [ MgO6] octahedra ） and T2 （ tetraheda forming six-reentered rings） tetrahedral sites. This resulted in a lattice deformation and increased the anharmonicity of polarization vibration, which is responsible for the improvement of infrared radiation properties of the substituted eordierites.
文摘An experimental study on infrared radiation from the hot jet by means of model test is presented. The infrared detection system of the universal infrared instruments. the testing method and experimental results of infrared radiation from the hot jet are introduced. The space distribution of infaed radiant energy. the spectrum of infrared radiation from the hot jet. the distribution of the radiant energy of the hot jet against the wavebands and the characteristic difference of the hot jet radiaton between the 2-D jet tube and the circular jet tube are obtained. It is indicated that the testing system and the method are valid and the results are in accord with the theoretical analysis.
基金Funded by the Key Project in Science and Technology Innovation Cultivation Program of Soochow University(Q3109808)
文摘Co1-xZnxFe2O4 ferrites were prepared by solid state reaction. The microstructure and performance were studied by X-ray diffraction, X-ray absorption fine-structure analysis and IRE-2 infrared radiant test. It is found that infrared radiance show a nonlinear change with x, exhibiting the infrared radiance of this material improved and the average radiance in the 8-14 μm waveband reached 0.91. The Co^3＋ and Zn^2＋ ions are found to occupy both tetrahedral and octahedral sites, and correspondingly, the fraction of Fe^3＋ ions in B-site decreases nonlinearly in ferrites. The lattice parameters are found to concern with Zn^2＋, and the activation energy deduces from crystal strain and crystal vibrate increases with content Zn^2＋. The redistribution of the Co^3＋ and Zn^2＋ ions between tetrahedral and octahedral sites is related to the providing a selective tetrahedral and octahedral sites infrared radiance of Co1-xZnxFe2O4 ceramics with increasing x.
基金Natural Science Foundation of China ( NSFC,Grant no. 51372255 )Beijing Natural Science Foundation ( BNSF,Grant no. 2131006 )+2 种基金International Science and Technology Cooperation Program of China ( Grant no. 2014DFR51010)External Cooperation Program of Chinese Academy of Sciences ( Grant no. GJHZ201310 )Open Foundation of State Key Laboratory of Advanced Refractories ( Grant no. 201401,Sinosteel Luoyang Institute of Refractories Research Co. ,Ltd. ) for the financial support
文摘Nowadays,it is a great challenge to reduce energy consumption and exhaust emission for human activities,in particular,high temperature industries.Among many efforts made to realize energy savings for high temperature furnaces and kilns,the use of high emissivity materials is considered to be an effective route to increase their thermal efficiency by enhancing heat transfer.Most materials with high refractoriness and superior chemical stability have weak infrared absorption and radiation properties;however,their emissivity in infrared regions（1 —25 μm） could be effectively increased by ion doping.This is attributed to three main mechanisms：1） distortion of the crystal lattice;2） increase of free carrier absorption; 3） formation of impurity energy level.In this paper,the development and advancement of various material systems with high emissivity including non-oxides and oxide based ceramics were reviewed.It is also suggested that the establishment of evaluation models or instruments for energy savings would be beneficial to design and application of high emissivity materials in various high-temperature environment.Furthermore,more efforts should be made on durability of high emissivity materials at high service temperatures and on the standardization of testing methods for emissivity.
基金supported by the National Defense Science and Technology Pre-Research Fund, China (No. KJXYY2019054/M51)。
文摘Hypersonic vehicles emit strong infrared radiation from their high-temperature exhaust plume and body, which is critical for infrared early warning, tracking, and guidance. In this work, a comprehensive analysis is conducted on the factors involved in air dissociation reaction within the shock layer of hypersonic missile heads, as well as the multi-component afterburning effect of the exhaust plume. A novel Reverse Monte Carlo Method(RMCM) is proposed for infrared radiation calculation, which utilizes two-dimensional Low-Discrepancy Sequences(LDS) to improve computational accuracy. The numerical calculations for a dagger-type missile show that afterburning reactions increase the temperature on the centerline of the outlet exhaust plume by about 1000 K. The total infrared radiation intensity of the missile is the highest in the 1–3 μm band, with the hightemperature wall of the nozzle being the primary source of solid radiation, and gas radiation primarily coming from H_(2)O. The radiation intensity of the missile exhaust plume in the 3–5 μm band is the highest, with radiation sources primarily coming from CO_(2), CO, and HCl. Afterburning reactions of the exhaust plume increase the total infrared radiation intensity of the missile by about 0.7times. These results can provide reference for the detection and guidance of hypersonic missiles.
文摘The temperature distributions on the helicopter airframe and in the exhaust plume are affected seriously by the engine exhaust system, rotor downwash and solar irradiance. To precisely simulate temperature distribution on the helicopter airframe and in the exhaust plume, the effects of rotor downwash and solar irradiance are considered in three-dimensional flow and heat transfer calculation under helicopter hovering. Based on the temperature distribution, a forward-backward ray tracing method is used to calculate the helicopter infrared （IR） radiation intensity. A numerical study is conducted on a fictitious helicopter model with an integrated exhaust system-tail airframe configuration, and the thermal and infrared radiation characteristics are analyzed.
文摘One of the most important problems of stealth technology is to evaluate the infrared radiation （IR） level received by IR sensors from fighters to be detected. This article presents a synthetic method for calculating the IR emitted from aircraftskin. By reck- oning the aerodynamic heating and hot engine casing to be the main heat sources of the exposed aircraft-skin, a numerical model of skin temperature distribution is established through computational fluid dynamics （CFD） technique. Based on it, an infrared signature model for solving the complex geometry and structure of a fighter is proposed with the reverse Monte Carlo （RMC） method. Finally, by way of determining the IR intensity from aircraft-skin, the aircraft components that emit the most IR can be identified; and the cooling effects of the main aircraft components on IR intensity are investigated. It is found that reduction by 10 K in the skin temperature of head, vertical stabilizers and wings could lead to decline of more than 8% of the IR intensity on the aircraft-skin in front view while at the broadside of the aircraft, the drops in IR intensity could attain under 8%. The results provide useful reference in designing stealthy aircraft.
基金the National Natural Science Foundation of China(Grant No.11072032)
文摘The infrared radiation signature of the plume from solid propellants with different energy characteristics is not the same. Three kinds of double-base propellants of different energy characteristics are chosen to measure the infrared spectral radiance from 1000 cm 1 to 4500 cm 1 of their plumes. The radiative spectrum is obtained in the tests. The experimental results indicate that the infrared radiation of the plume is determined by the energy characteristics of the propellant. The radiative transfer calculation models of the exhaust plume for the solid propellants are established. By including the chemical reaction source term and the radiation source term into the energy equation, the plume field and the radiative transfer are solved in a coupled way. The calculated results are consistent with the experimental data, so the reliability of the models is confirmed. The temperature distribution and the extent of the afterburning of the plume are distinct for the propellants of different energy characteristics, therefore the plume radiation varies for different propellants. The temperature of the fluid cell in the plume will increase or decrease to some extent by the influence of the radiation term.
文摘Hot air(HA)drying of banana has low drying efficiency and results in undesirable product quality.The objectives of this research were to investigate the feasibility of infrared(IR)heating to improve banana drying rate,evaluate quality of the dried product,and establish models for predicting drying characteristics.Banana slices of 5 mm and 8 mm thickness were dried with IR and HA at product temperatures of 60℃,70℃ and 80℃.Banana drying characteristics and changes in residual polyphenol oxidase(PPO),Hydroxymethylfurfural(HMF),color,moisture content(MC)and water activity during the treatments were investigated.Results showed that significant moisture reduction and higher drying rates were achieved with IR drying compared to HA drying in the early stage.The drying data could be fitted to the Page model for accurate prediction of MC change for IR and HA drying with mean R2 of 0.983.It was noted that enzyme inactivation occurred more quickly with IR than with HA drying.A unique response of PPO under IR and HA drying was revealed.IR heating of banana inactivated PPO within the first 20 min of drying at 60℃,70℃ and 80℃,while PPO was first activated before inactivation at 60℃ and 70℃ drying with HA.The highest HMF content occurred in banana slices with 5 mm thickness dried with IR at a product temperature of 80℃.It is therefore recommendable to dry banana with IR at product temperature of 70℃ or below to preserve the product quality.These findings are new and provide more insight in the application of IR heating for drying banana for improved drying rate and product quality.
基金supported by the National Nature Science Foundation of China (No. 50771014)
文摘Boron for aluminum substitution in the cordierite structure has been examined by sol-gel preparation of different samples along the compositional junction Mg2Al4-xBxSi5O18 with x=0,0.5,1,1.5.By increasing the x value from 0 to 1.5 the crystallization behavior changed accordingly.Proper amount B2O3 doping can promote the sintering of amorphous cordierite gel,effectively restrain the precipitation of μ-cordierite and enhance the crystallization of α-cordierite.The substitution of B3＋ for Al3＋ in cordierite crystal structure can effectively improve the near-infrared spectral emissivity of this cordierite based glass-ceramics.
基金co-supported by the National Natural Science Foundation of China (Nos. 51376065 and 51176052)Guangdong Key Scientific Project (No. 2013B010405004)
文摘This study seeks to determine the similarities in plume radiation between reduced and full-scale solid rocket models in ground test conditions through investigation of flow and radiation for a series of scale ratios ranging from 0.1 to 1. The radiative transfer equation (RTE) considering gas and particle radiation in a non-uniform plume has been adopted and solved by the finite volume method (FVM) to compute the three dimensional, spectral and directional radiation of a plume in the infrared waveband 2-6 mu m. Conditions at wavelengths 2.7 mu m and 4.3 mu m are discussed in detail, and ratios of plume radiation for reduced-scale through full-scale models are examined. This work shows that, with increasing scale ratio of a computed rocket motor, area of the high-temperature core increases as a 2 power function of the scale ratio, and the radiation intensity of the plume increases with 2-2.5 power of the scale ratio. The infrared radiation of plume gases shows a strong spectral dependency, while that of Al2O3 particles shows spectral continuity of gray media. Spectral radiation intensity of a computed solid rocket plume's high temperature core increases significantly in peak radiation spectra of plume gases CO and CO2 center dot Al2O3 particles are the major radiation component in a rocket plume. There is good similarity between contours of plume spectral radiance from different scale models of computed rockets, and there are two peak spectra of radiation intensity at wavebands 2.7-3.0 lm and 4.2-4.6 lm. Directed radiation intensity of the entire plume volume will rise with increasing elevation angle. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.
文摘A multi-scale narrow band correlated-k distribution（MSNBCK） model is developed to simulate infrared radiation（IR） from an exhaust system of a typical aircraft engine.In this model,an approximate approach instead of statistically uncorrelated assumption is used to treat overlapping bands in gas mixture.It significantly reduces the requirement for computing power through converting the exponential increase of computing power consumption with the increase of participating gas species to linear increase.Besides,MSNBCK model has a great advantage compared with conventional methods which can estimate each species＇ contribution to the total gas mixture radiation intensity.Line by line（LBL） results,experimental data and other results in the references are used to evaluate this new model,which demonstrates its advantage in terms of accuracy and computing efficiency.By coupling this model and finite volume method（FVM） into radiative transfer equation（RTE）,a comparative study is conducted to simulate IR signature from the exhaust system.The results indicate that wall＇s IR emission should be considered in both 3-5 μm and8-14 μm bands while gases＇ IR emission plays an important role only in 3-5 μm band.For plume IR radiation,carbon dioxide＇s emission is much more significant than that of water vapor in both3-5μm and 8-14 μm bands.Especially in 3-5 μm band,the water vapor＇s IR signal can even be neglected compared with that of carbon dioxide.
基金financial supports for this project from the National Science and Technology Major Project of China(No.J2019-III-0009-0053)。
文摘To address deeper understandings about the aero-thermal performance of an integrating infrared suppressor under more realistic situations,a numerical investigation is motivated in the current study,concerning the effects of forward-flight speed on exhaust plume flow and infrared radiation of the Infrared Suppressor-integrating(IRS-integrating)helicopter,wherein the forward-flight speed is changed from 0 m/s(hover state)to 100 m/s,while both the engine exhaust parameters and the main-rotor operation parameters remains unchanged during different forward-flight velocities.The results show that the interaction between forward-flight flow and downwash flow alters the exhaust plume development and the internal flow inside the IRS-integrating rear fuselage more complicatedly,tightly dependent on the forward-flight speed.Of particular concern is the situation where the forward-flight flow has nearly the same level as the downwash flow,the hot mixing flow could possibly interacts with the helicopter rear fuselage to play a local heating effect.With the increase of forward-flight speed,the ejection coefficient is generally increased and the average exhaust temperature of mixing flow is decreased,leading to a reduction of the infrared radiation intensity of exhaust plume in 3–5 lm band.However,the influence of forward-flight speed on the overall infrared radiation intensity of IRS-integrating helicopter is conjectured not monotonous due to the complicated interaction between forward-flight flow and downwash flow.Under high-speed forward-flight states,the overall infrared radiation intensity of the IRS-integrating helicopter in 3–5 lm band is reduced with the increase of forward-flight speed.With respect to 3–5 lm band,the forward-flight speed has little effect on the infrared radiation in 8–14 lm band.
