用于超声速和高超声速导弹的透电磁辐射复合窗口

介绍了一种用于超声速或高超声速导弹的导引头窗口,该窗口可传输电磁辐射波,由互相支持的窗口层组成。讨论了窗口层的材料、厚度和排列方式。给出了这种窗口的结构图形,并详细阐述了系统的工作原理。

Simultaneous Identification of Thermophysical Properties of Semitransparent Media Using a Hybrid Model Based on Artificial Neural Network and Evolutionary Algorithm

A hybrid identification model based on multilayer artificial neural networks(ANNs) and particle swarm optimization(PSO) algorithm is developed to improve the simultaneous identification efficiency of thermal conductivity and effective absorption coefficient of semitransparent materials.For the direct model,the spherical harmonic method and the finite volume method are used to solve the coupled conduction-radiation heat transfer problem in an absorbing,emitting,and non-scattering 2D axisymmetric gray medium in the background of laser flash method.For the identification part,firstly,the temperature field and the incident radiation field in different positions are chosen as observables.Then,a traditional identification model based on PSO algorithm is established.Finally,multilayer ANNs are built to fit and replace the direct model in the traditional identification model to speed up the identification process.The results show that compared with the traditional identification model,the time cost of the hybrid identification model is reduced by about 1 000 times.Besides,the hybrid identification model remains a high level of accuracy even with measurement errors.

Deformation defects and electron irradiation effect in nanostructured Al-Mg alloy processed by severe plastic deformation

In order to explore the exact nature of deformation defects previously observed in nanostructured Al-Mg alloys subjected to severe plastic deformation, a more thorough examination of the radiation effect on the formation of the planar defects in the high pressure torsion （HPT） alloys was conducted using high-resolution transmission electron microscopy （HRTEM）. The results show that high density defects in the HRTEM images disappear completely when these images are exposed under the electron beam for some duration of time. At the same time, lattice defects are never observed within no-defect areas even when the beam-exposure increases to the degree that holes appear in the areas. Therefore, it is confirmed that the planar defects observed in the HPT alloys mainly result from the significant plastic deformation and are not due to the radiation effect during HRTEM observation.

温室效应与地球环境变暖

什么是温室效应? 月球上白天的温度可达120℃,夜间温度可低到-180℃以下。月球上昼夜温差大,因为月球没有大气包围着它。地球由于有大气包围,太阳的辐射透过大气层射到地面,地面增温后向外放出的热量,绝大部分被大气吸收,使大气增温。大气在增温的同时,也向外辐射能量,一小部分能量向外射向宇宙空间。

Solar Radiation Penetrating Through Sea Ice Under Very Low Solar Altitude

Based on the optical data for transmitted radiation through sea ice in the Arctic during the late autumn and early winterof 2007,the authors studied the arriving solar radiation,reflected radiation and transmitted radiation under very low solar altitude.Through the atmosphere,the light of the arriving solar radiation at short wavelength was weakened,with the spectral distribution ofdouble peaks centered at 490 nm and 683 nm.The magnitude of the peak at 683 nm even exceeded that at 490 nm under the very lowsolar radiation condition.The reflection was lower than that in summertime because of the thin thicknesses of ice and snow,allowinghigher ratio of heat to enter the sea ice and snow.When higher ratio of solar radiation entered sea ice in late autumn,the new icefreezing would be affected.The spectral reflectivity from snow surface was almost a constant,but the reflection without snow de-creased at longer wavelengths.In the transmission spectrum,the light of 490 nm was dominant.It indicates that the radiation atlonger wavelength was weakened by sea ice.Therefore,under the condition of low solar altitude,the radiation at shorter wavelengthwas weakened by the atmosphere while the radiation at longer wavelength was weakened by the sea ice.The combined effect of at-mosphere and sea ice made the solar radiation under sea ice much weaker.The absorption of sea ice for the longer-wavelength radiation allowed the sea ice to gain more heat to slow down the freezing process.

A review of light amplification by stimulated emission of radiation in oil and gas well drilling

The prospect of employing Light Amplification by Stimulated Emission of Radiation(LASER) for well drilling in oil and gas industry was examined.In this work,the experimental works carried out on various oil well drilling operations was discussed.The results show that,LASER or LASER-aided oil and gas well drilling has many potential advantages over conventional rotary drilling,including high penetration rate,reduction or elimination of tripping,casing,bit costs,enhanced well control,as well as perforating and side-tracking capabilities.The investigation also reveals that modern infrared LASERs have a higher rate of rock cuttings removal than that of conventional rotary drilling and flame-jet spallation.It also reveals that LASER can destroy rock without damaging formation permeability but rather,it enhances or improves permeability and that permeability and porosity increases in all rock types.The paper has therefore provided more knowledge on the potential value to drilling operations and techniques using LASER.

Characteristics of Solar Radiation and the Impact of Clouds at Yangbajing, Tibet

Yangbajing (YBJ) is located in the Tibetan Plateau, China. The characteristics of solar radiation and its relationship with clouds at YBJ from April 2009 to April 2010 were analyzed in this paper. The annual mean solar radiation was 478.4 W m 2 , and the annual mean transmittance was 0.713. The atmospheric mean trans- mittance of clear skies reaches 0.828 when the solar elevation angle (SEA) is greater than 10 degrees. Comparisons with numerical simulations show that the atmosphere of YBJ is clean. Impacts from atmospheric conditions on solar radiation are similar for clear skies during the year because the standard deviation of transmittance in clear skies was less than 0.05 when the SEA was greater than 10 degrees. It is important to understand the impact of clouds on solar radiation without considering other impact factors. In the last part of this article, the authors analyzed and established a statistical quantitative relationship between surface solar radiation and cloud fraction.

TEM Foil Preparation from Irradiated Metallic Materials： A Practical Approach

This paper focuses on work related to post irradiation examination of 300-series austenitic stainless steel taken from reactor vessel internals of PWR. High neutron irradiation dose in NNP＇s leads to a degradation of microstructure of the material in a nano-metric scale. Hence, it is important to characterize the irradiated materials to understand the physical basis of the degradation mechanisms. Microstructural characterization of neutron-irradiated materials by TEM requires enhanced sample preparation methodologies, which commonly needs general improvements regarding particular experiment to be performed. In this study, the authors have developed methodology specialized in 1 mm TEM thin foil preparation from a deformed shank of a broken miniaturized tensile specimen. TEM foil size in current studies is smaller than standard because of the small shank diameter and high radioactivity of the studied material. The reduction of the TEM foil radioactivity to minimum is crucial to perform EDX chemical analysis and to increase the EDX detector lifetime. This paper describes whole process from bulk sample handling, including remote-controlled material cutting in shielded hot-cells and disc polishing in glow-boxes, up to the final procedure of electrolytic-polishing of electron transparent 1 mm TEM foils. Eventually, results of TEM microanalysis of radiation-induced defects were present.

On the combined heat transfer of natural convection, radiation and conduction in the non-gray semitransparent thermal fibrous insulation

A detailed numerical modeling is performed to investigate heat transfer in high-porous, high-temperature non-gray semitransparent silica insulation materials. Radiation between fibers, conduction within fibers and convection from the fibers to the surrounding fluid are considered. Macroscopic (porous media) modeling is used to determine the velocity, pressure and temperatures fields for fibrous insulation with a random packing geometry under natural convection. Based on a non-gray application of the solution to the radiative transfer equation, the value of the refractive index(n,m)is used to generate macroscopic average radiative properties such as extinction coefficient, scattering albedo and phase function. Key features of the macroscopic model include two-dimensional effects,non-gray radiative exchange, and the relaxation of the local thermodynamic non-equilibrium. The effectiveness of this numerical model is validated by the previous experimental data.

Preparation and Properties of Glass with High Transmittance and Intense Gamma Ray Shielding

Introduction As a kind of high-energy electromagnetic radiation,gamma rays can lead to radiation effect and environmental pollution.To ensure the reliability and safety utilization of gamma radiations in different areas,materials with reliable gamma shielding performances should be developed.The existing efforts are to use glasses as alternative for the conventional radiation shielding materials.As a typical window material,glass itself has attracted wide attention due to its unique chemical and physical advantages.Among them,lead-based radiation shielding materials are widely used in the field of ionizing radiation protection due to their reliable physical properties.In the nuclear industry and high energy physics laboratories,different materials can be used for temporary or permanent shielding.The lead-based glass doped with heavy metal oxide PbO is widely used in the field of radiation shielding for a long time with reliable light transmission properties,which facilitates the observation and monitoring of radiation areas.In this paper,three kinds of transparent silicate glass with different PbO contents were prepared by a high-temperature melting forming method.The gamma-rays protection abilities of the three kinds of glass were investigated through experimental and thermotical methods.The chemical and thermal stability of the glass were also analyzed.In addition,the influence mechanism of the structure and performance differences of the three kinds of glass was also discussed.Methods Analytical pure quartz sand(SiO_(2),purity 99.5%,in mass,the same below),lead monoxide(PbO,purity 99.0%),potassium nitrate(KNO3,purity 99.0%)and sodium nitrate(NaNO3,purity 99.0%)were selected as raw materials for preparation of three kinds of gamma-rays shielding glass materials by a high-temperature melting method.An appropriate amount of raw materials was thoroughly mixed and added to 3 L quartz crucible and heated in air at 1200℃.Then the raw materials were melted at 1250℃for 14 h.The uniform melt was quickly poured into the 150 mm×150 mm×50 mm stainless steel mold preheated at 750℃.Finally,the quenched glasses were annealed at 450℃for 12 h and cooled naturally to room temperature.The density of the three glass samples was tested based on the Archimedes principle.The thermal expansion coefficient of glass samples was measured by a model Netzsch DIL 402 expansion coefficient tester.The infrared spectra were measured by a model Perkinelmer Spectrum 100 FTIR Spectrometer.The Raman spectra were tested by a model HORIBA LabRAM HR800 high-resolution Raman spectrometer.The gamma ray shielding test was completed in China Academy of Engineering Physics.The chemical stability test was completed in Chengdu Guangming Glass Co.,LTD.The acid stability and moisture stability of the glass samples were tested according to the national standards GB/T 7962.14-2010 and GB/T 7962.15-2010,respectively.The thermal stability of the galss was also determined.Results and discussion Glass structure becomes more compact with the exchange of Pb alternatives of Si,K and Na.Increasing the density of glass is conducive to improving its shielding performance,but this leads to significant changes in the optical properties,thermal properties and chemical stability of glass due to the increase of heavy metal content.The preparation of high transmittance glass is more difficult.The coefficient of thermal expansion of glass samples gradually decreases from 103.6×10^(-7)℃-1 to 89.2×10^(-7)℃-1,and the values of Tg and Tf also decrease with the increase of mass fraction of PbO in glass components.The change of the thermal properties of the three glass samples is a result of the joint action of PbO,Na2O and K2O.The FTIR spectra show that the added PbO is transformed into[PbO4]units with 4 coordination numbers into the network under the condition of sufficient free oxygen as PbO content in the glass increases.These[PbO4]units participate in the formation of silicate networks.The Raman spectra indicate that the silicate network structure is de-polymerized as PbO content is increased,and the enhancement of the characteristic vibrational peaks corresponding to the Pb-Si-O indicates an increase in the degree of participation of the[PbO4]units in the formation of silicate network. The ion packing density of the glass sample gradually increases with the increase of PbO content,which shows that the compressible free volume per unit volume of the glass sample becomes smaller. PbO with a high concentration(x = 0.50 and x = 0.66) is used as a glass-forming agent, and the [PbO4] structural units can form a connection structure with thesilicon oxide tetrahedron, which plays a role in repairing the glass network.The permeability of the glass can be improved via strictly controlling the iron content of the introduced raw materials andmaking full use of the double alkali effect of the glass. The actual shielding performance of glass is not a result of simple addition ofvarious components. This can be affected by the actual composition content of the glass, melting process and endoplasmic uniformity.The influence of glass expansion coefficient on the thermal stability is much greater than that on its chemical stability.Conclusions PbO with a high concentration (x = 0.50 and x = 0.66) was used as a glass-forming agent, and the [PbO4] structuralunits could form a connection structure with the silicon oxide tetrahedron, playing a role in repairing the glass network. The measuredshielding rate of 60Co gamma-ray could be 50% and the glass with 50% PbO content (in mass fraction) exhibited a lineartransmission rate of more than 85% in the range of 400-800 nm. In addition, the reliable thermal and chemical stabilities were alsoreflected in the glass.

LED路灯散热器高辐射散热涂层材料的选择

借鉴光学增透膜的概念,提出在辐射散热涂层和LED路灯基板之间增加一层增热层,称之为辐射增透层,从而可以提高辐射散热在LED路灯中的降温作用。文章通过对薄膜透射光谱对增热层可能选用的材料进行了对比分析,选出较合适加工辐射增透层的材料。

Assessment and analysis of microwave emissivity and transmissivity of a deciduous forest towards the estimate of vegetation biomass

Forests play an important role in the global carbon cycle and have a potential impact on global climatic change.Monitoring forest biomass is of considerable importance in understanding the hydrological cycle.Because of the problem of dense forest cover,no reliable method with which to retrieve soil moisture in forest areas from the microwave emission signature has been established.All of these issues relate to the microwave emissivity and transmissivity characteristics of a forest.The microwave emission contribution received by a sensor above a forest canopy comes from both the soil surface and the vegetation layer.To analyze the relationship of forest biomass and forest emission and transmissivity,a high-order emission model,the matrix-doubling model,which consists of both soil and vegetation models,was developed and then validated for a young deciduous forest stand in a field experiment.To simulate the emissivity and transmissivity of a deciduous forest in the L and X bands using the matrix-doubling model,the parameters of components of deciduous trees when the leaf area index varies from 1 to10 were generated by an L-system and a forest growth model.The emissivity and transmissivity of a forest and the relationships of these parameters to forest biomass are presented and analyzed in this paper.Emissivity in the L band when the leaf area index is less than 6 and at viewing angles less than 40°,and transmissivity in the L band are the most sensitive parameters in deciduous forest biomass estimation.

Radiative entransy flux in enclosures with non-isothermal or non-grey,opaque,diffuse surfaces and its application

The spectral radiative entransy flux and the total radiative entransy flux are defined for the steady radiative heat transfer processes in enclosures composed of non-isothermal or non-grey, opaque, diffuse surfaces. Based on the definitions, the radiative entransy flux balance equation and the radiative entransy dissipation functions are introduced under spectral and total wavelength condition. Furthermore, the minimum principle of radiative entransy loss, the extreme principle of radiative entransy dissipation and the minimum principle of radiative thermal resistance are developed. The minimum prirlciple of radiative en- transy loss shows that the potential and the net radiative heat flux distribution which meet the control equations and the boundary conditions would make the radiative entransy loss minimum if the net radiative heat flux or the potential distribution of the radiative heat transfer system is given. The extreme principle of radiative entransy dissipation indicates that the minimum radiative entransy dissipation leads to the minimum average potential difference for the prescribed total radiative heat exchange and the maximum radiative entransy dissipation leads to the maximum radiative heat exchange for the prescribed average potential difference. Moreover, the minimum principle of radiative thermal resistance tells us that the aforementioned extreme values of radiative entransy dissipation both correspond to the minimum value of radiative thermal resistance. Application examples are given for the extreme principle of spectral radiative entransy dissipation and the minimum principle of spectral radiative thermal resistance, and the principles are proved to be applicable.

Inverse Radiation Problem of Boundary IncidentRadiation Heat Flux in Semitransparent Planar Slabwith Semitransparent Boundaries

An inverse method is presented for estimating the unknown boundary incident radiation heat flux onone side of one-dimensional semitransparent planar slab with semitransparent boundaries from theknowledge of the radiation intensities exiting from the other side. The inverse problem is solved usingconjugate gradient method of minimization based on discrete ordinates method (DOM) of radiativetransfer equation. The equations of sensitivity coefficients are derived and easily solved by DOM, withthe result that the complicated numerical differentiation commonly used in solving sensitivity coefficients is avoided. The effects of anisotropic scattering, absorption coefficient, scattering coefficient,boundary reflectivity, fluid temperature outside the boundaries, convection heat transfer coefficients,conduction coefficient of semitransparent media and slab thickness on the accuracy of the inverse analysis are investigated. The results show that the boundary incident radiation heat flux can be estimatedaccurately, even with noisy data.

Ultrasound responsive organogels based on cholesterol-appended quinacridone derivatives with mechanochromic behaviors

A series of cholesterol-appended quinacridone (QA) derivatives 1a-1d have been synthesized,in which 1b and 1c could form stable organogels in a wide range of organic solvents upon ultrasound irradiation.Field emission scanning electronic microscope (FESEM) and transmission electron microscopy (TEM) of xerogels or precipitates indicated that 1b and 1c formed 1D fibrous nanostructure,while 1a assembled into 3D flower-like microstructures.The ultrasound-induced organogel process was characterized by kinetic UV-vis and photoluminescence spectroscopic methods suggesting the formation of ?-? aggregates in the gel state.Experimental results demonstrated that the ultrasound could promote molecules to contact frequently in the solution and induce semistable initial aggregates,which propagate to form nano/micro superstructures.The aggregation model was optimized by semiempirical AM1 calculation suggesting the hierarchical self-assembly process.In addition,the formed xerogel film exhibited mechanochromic property,and the phase transition process was accompanied by the fluorescence changes between yellowish green and orange.

Inverse Radiation Problem in One-DimensionalSemitransparent Plane-Parallel Media

The discrete ordinates method is used to develop a solution to an inverse radiation problem of source term in one-dimensional semitransparent plane-parallel media with opaque and specularly reflecting boundaries. It is assumed that, with the exception of the inhomogeneous source term, all aspects of the radiation transport problem are known. A method is developed to determine the inhomogeneous source term from specified incident radiation intensities on the boundaries. The inverse problem is solved using conjugate gradient method that minimizes the error between the incident radiation intensities calculated and the experimental data. The effects of singl-scattering albedo, scattering asymmetry parameter, wall emissivity, the diffuse fraction of reflectivity, and the optical thickness on the accuracy of the inverse are investigated. The results show that the source term can be estimated accurately, even with noisy data.

A Method for Measuring Thermal Radiation Properties of Semi-Transparent Films

This paper presents a method(F method)for determining the optical constants and the thicknesses of semi- transparent thin films.It has the following distinctive features:high precision;rapid determination of the measured quantities;wide range of convergence of solutions;capable of judging whether or not the results are reasonable.In order to meet the needs of application and engineering design,a family of curves designated Fig.n-F was prepared.Using it n,k,d of the films can be conveniently and accurately determined.From the optical constants and the thicknesses of the films determined by the F method,all important thermal radiation properties of the semi-transparent films needed in application can be obtained.

Microstructures of the interlayer in Mo/Si multilayers induced by proton irradiation

In this work,the microstructure and optical properties of the Mo/Si multilayers mirror for the space extreme-ultraviolet solar telescope before and after 100 keV proton irradiation have been investigated.EUV/soft X-ray reflectometer(EXRR) results showed that,after proton irradiation,the reflectivity of the Mo/Si multilayer decreased from 12.20% to 8.34% and the center wavelength revealed red shift of 0.38 nm,as compared with those before proton irradiation.High-resolution transmission electron microscopy(HRTEM) observations revealed the presence of MoSi 2,Mo 3 Si and Mo 5 Si 3 in Mo-on-Si interlayers before irradiation.The preferred orientation such as MoSi 2 with(101) texture and Mo 5 Si 3 with(310) texture was formed in Mo-on-Si interlayers after proton irradiation,which led to the increase of thickness in the interlayers.It is suggested that the changes of microstructures in Mo/Si multilayers under proton irradiation could cause optical properties degradation.