首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The experiments pertaining to the excitations of Lyman- radiation in the night sky are reviewed. Various possible modes of excitation are considered. Scattering of solar L in interplanetary hydrogen is not suitable because of an insufficient amount of hydrogen and difficulty in accounting for the large night time albedo contrasted with the small daytime value. Transport by multiple scattering in the exosphere produces an appreciable excitation as well as the correct variation of intensity as function of zenith angle. However, the process fails by a factor of 4 for a solar flux of 6 ergs/cm2 sec and the 3 × 1012 atoms/cm2 geocorona consistent with absorption measurements. A direct scattering in a geocoma far from the earth overcomes the albedo and thin atmosphere problems. However, there is difficulty in accounting for the presence of the amount of hydrogen necessary beyond 15 earth radii. Also the absence of H excitation by Lyman- is a problem. No explanation so far proposed appears adequate. Experiments are suggested.  相似文献   

2.
Recentlythewholeindustrysufferdfromthelostgreatly.ItissaidthatCAACwillcarryoutaseriesofsolutionssuchaslindtingthetransportcapabilityinput,thescoPeoftheticketpricediscountaswellasthepricerateoftheagentstochangethedisorderofthepricecompetitionsandputanendtothedownslideoftheeconomicefficiency.However,therealwayoutistoenhancethecompetenceofthecivilaviationindustryallaround.ThecausesanalyzedbyPeoPleinthiscirclecanbeconcludedastheslowdownofthenationaleconondcdevelopingsPeed,thefinancialcrisisofth…  相似文献   

3.
AlthoughhitbyboththeAsianfinancialcrisisandtheseveresummerfloods,Chineseeconomystillobtained4growthrateof7.8%in1998,andthetaxcollectedaccordinglyachievedanincreaseofRMB100billionyuan,whichlaidagoodfoundationforimprovingtheeconondcoperationenvironmentin1999.Howeverwhenboththerailwayandthepost&telecommunicationindustryspeededuptheirconstruction,thedevelopmentofChinesecivilaviahonindustryappearedweak.Eventhoughin1998thetransportationvolumesofthewholeindustrywerecompletedfairly,thestatCownedairi…  相似文献   

4.
This study is aimed at predicting the relationship between the meniscus and the quality of the sapphire crystals produced by the micro-pulling and shoulder at cooled center (SAPMIC) technique. As with different orientations, the shapes of the meniscus vary, so an investigation into the anisotropy of the meniscus shapes is very important for the final quality of the sapphire crystal. An effective model to describe meniscus shapes and their formation process has been presented. The model has been applied to a sapphire crystal of 200 mm diameter in order to check its reliability. The results show that the model proves to be useful for forecasting the final shapes of the sap-phire crystal made by the SAPMIC technique.  相似文献   

5.
At present there is no doubt that the local interstellar medium (LISM) is mainly partially ionized hydrogen gas moving with a supersonic flow relative to the solar system. The bulk velocity of this flow is approximately equal ~26 km/s. Although the interaction of the solar wind with the charged component (below plasma component) of the LISM can be described in the framework of hydrodynamic approach, the interaction of H atoms with the plasma component can be correctly described only in the framework of kinetic theory because the mean free path of H atoms in the main process of the resonance charge exchange is comparable with a characteristic length of the problem considered. Results of self-consistent, kinetic-hydrodynamic models are considered in this review paper. First, such the model was constructed by Baranov and Malama (J. Geophys. Res. 98(A9):15,157–15,163, 1993). Up to now it is mainly developed by Moscow group taking into account new experimental data obtained onboard spacecraft studying outer regions of the solar system (Voyager 1 and 2, Pioneer 10 and 11, Hubble Space Telescope, Ulysses, SOHO and so on). Predictions and interpretations of experimental data obtained on the basis of these models are presented. Kinetic models for describing H atom motion were later suggested by Fahr et al. (Astron. Astrophys 298:587–600, 1995) and Lipatov et al. (J. Geophys. Res. 103(A9):20,631–20,642, 1998). However they were not self-consistent and did not incorporate sources to the plasma component. A self-consistent kinetic-hydrodynamic model suggested by Heerikhuisen et al. (J. Geophys. Res. 111:A06110, 2006, Astrophys. J. 655:L53–L56, 2007) was not tested on the results by Baranov and Malama (J. Geophys. Res. 111:A06110, 1993) although it was suggested much later. Besides authors did not describe in details their Monte Carlo method for a solution of the H atom Boltzmann equation and did not inform about an accuracy of this method. Therefore the results of Heerikhuisen et al. (J. Geophys. Res. 111:A06110, 2006) are in open to question and will not be considered in this review paper. That is why below we will mainly consider a progress of the Moscow group on heliospheric modelling endeavours in the kinetic-hydrodynamic approach. Criticism of the models that treat interstellar hydrogen in the heliosphere as several fluids is given. It is shown that the multi-fluid models give rise to unreal results especially for distributions of neutral component parameters. Magnetohydrodynamic (MHD) modelling of the solar wind interaction with the LISM gas is also reviewed.  相似文献   

6.
The feasibility was investigated to substitute chrome-free passivation treatment of electrodeposited zinc in a titanium bath for chromate passivation treatment. The formation mechanism of the chrome-free passivation film was further analyzed. The surface mor- phologies and the elemental compositions of the treated samples with varied immersion times were observed by scanning electron mi- croscopy (SEM) and determined by energy dispersion spectrometry (EDS), respectively. The electrode potential of the sample surface was recorded in the film formation process. The changes of the electrode potential are in accordance with that of SEM and EDS of the sample surface. The results of X-ray photoelectron spectroscopy (XPS) show the chrome-free passivation film composed of ZnO, SiO2, TiO2, Zn4Si2O7(OH)2, and SrF2. The anode zinc dissolution and the local pH value increase due to the cathode hydrogen ion reduction process result in the formation of the chrome-free passivation film. The macro-images of the chrome-free passivation films formed on electrodeposited zinc show that the color of the film changes from blue to iridescence with the increase of the immersion times.  相似文献   

7.
The random models of open-cell foams that can reflect the actual cell geometrical properties are constructed with the Voronoi technique. The compression process of elastic open-cell foams is simulated with the nonlinear calculation module of finite element analysis program. In order to get the general results applicable to this kind of materials, the dimensionless compressive stress is used and the stress-strain curves of foam models with different geometrical properties are obtained. Then, the influences of open-cell geometrical properties, including the shape of strut cross section, relative density and cell shape irregularity, on the compressive nonlinear mechani- cal performance are analyzed. In addition, the numerical results are compared with the predicted results of cubic staggering model. Numerical results indicate that the simulated results reflect the compressive process of foams quite well and the geometrical properties of cell have significant influences on the nonlinear mechanical behavior of foams.  相似文献   

8.
A phase-field method was employed to study the influence of elastic field on the nucleation and microstructure evolution. Two kinds of nucleation process were considered:one using fixed nucleation probability and the other calculated from the classical nucleation theory. In the latter case, the simulated results show that the anisotropic elastic strain field yields significant effects on the behavior of nucleation. With a large lattice misfit between the matrixes and the precipitates, the nucleation process does not appear fully random but displays some spatial correlation and has a preference for the elastic soft direction. However, with a small lattice misfit, this bias does not look quite clear. On the contrary, in the case of fixed nucleation probability, the elastic field has no influence on the nucleation proc- ess. The lattice mismatch also exerts influences on the microstructure morphology: with lattice mismatch becoming larger, the micro- structure proves to align along the elastic soft direction.  相似文献   

9.
Afterfouryearshardwork,thekeyprojectoftheNinthFive-YearPlan,thePudongInternationalAirportputintooperationoffciallyonSep.l6th,l999.Thisfirst-classinternationalairportwiththetotalinvestmentofRMBl3obillionyuanindicatedthattheconstructionlevelofthecivilaviationairPortcameuptoanewstage.ShanghaibecomesthefirstcityinChinawhichhastwointernationallargeairPorts.Therefore,it'shelpfultopromoteShanghaitothemodernintemationalme-tropolisinthe2lstCentury.It'salsobeneficialforbuildingShanghaiandPudonge…  相似文献   

10.
Hexagonal-plate BaFe12O19 nano-particles were prepared by combining the co-precipitation and molten-salt method. The effects of molten-salt NaCl on the products have been compared with those of KCl. The X-ray diffraction analysis, the environment scanning electron microscopy and the vibrating sample magnetometer were used to measure their characteristics. The results show that the mol- ten-salt KCl is helpful to obtain pure phase while the molten-salt NaCl will prompt the crystallinity of particles to increase. It is also found that, given the molten-salt of NaCl and that of KCl of the same quantity, the particles formed are also the same size. The size of particles slightly increases as the quantity of the salt increases. Moreover, the sample prepared under 200% NaCl salt system has magnetization of 71.5 emu/g.  相似文献   

11.
Hexagonal-plate BaFe12O19 nano-particles were prepared by combining the co-precipitation and molten-salt method. The effects of molten-salt NaCl on the products have been compared with those of KCl. The X-ray diffraction analysis,the environment scanning electron microscopy and the vibrating sample magnetometer were used to measure their characteristics. The results show that the mol-ten-salt KCl is helpful to obtain pure phase while the molten-salt NaCl will prompt the crystallinity of particles to increase. It is also found that, given the molten-salt of NaCl and that of KCl of the same quantity, the particles formed are also the same size. The size of particles slightly increases as the quantity of the salt increases. Moreover, the sample prepared under 200% NaCl salt system has mag-netization of 71.5 emu/g.  相似文献   

12.
The effect of electromagnetic stirring on the inner quality of K417 superalloy ingots is studied with EPMA and optical microscope.The results show that while an electromagnetic stirring with 50Hz frequency and 80A current is imposed,the equiax crystals of K417 superalloy ingots can be effectively refined and increased,and the central shrinkage porosity and the dendritic segregation of K417 superalloy ingots are greatly reduced,so the inner quality of K417 superalloy ingots is obviously improved.  相似文献   

13.
ThenewroundofthereformofChinacivilaviationhasbeenstarted.Inrestrospectingthepast,allthedevelopmentdependsgreatlyonreform,suchasthewaytoturnChinacivilaviationintoenterprisesin1980s,themanagementsystemreformofdivisionbetweenadAnnistrahonandenterprises,themanagementdivisionbetweenairlinesandairPortsinthebegirmingof1990s.Asaresult,wecansaythatreformprovidesapoweffolenergytotherapidcontinuousdevelopmentofChinacivilaviation.Intheturnofthecentury.Chinacivilaviationalsomeetswithmanydifficultieswitht…  相似文献   

14.
OnNov.2,1949,thenewlybomgovemmentofthePeople'sRepublicofChinasetupCivilAviationAdndnistrationofChina(CAAC)underthePeople'sRevolutionaryMilitaryCommission.Forthe50years,Chinahasgrownintotheworldgiantinairtransport.1.FleetConstructionChineSeairlineshadatotalof523COIYnneededinl998,wtl.6timesandl64bomoreha3oedinlosoand78ndinlor8.~anedtalzzrtinlosoanu82edinl978,whileinl998,theaVeragrSeatsofeachedgreWtol6().ThetranpecaPabilityofl998reacanloor8.8tons,wtawas9.2bondl`s.4bowrthaforotl95oanulo…  相似文献   

15.
OnAngust13,ChinaEasternAirGroupandChinaEasternAirlinsCo.,Ltd.signedanagreementoftheentirecooperationwithIndustrial&CommerialBankofChina,whichstipulatedthatthebankwouldofferChillEastemaeredhatofRMB30billionyuanandtheall-aroundfinancialservicetill2000.Accodringtotheagreement,ChinaEastheAirlinesCo.,Ltd.,thecoreofthegroup,willreceiveanaircraft-leasingguaranteecreditlindtof$2.5billionandcreditlndofloansinforeignexchangeofRMB9billionyuan,besides,theothersubsidiariesofthegroupwillbeoffereda…  相似文献   

16.
Schindler  Sabine 《Space Science Reviews》2002,100(1-4):299-309
A summary of various measurements of the mean matter density in the universe, m, is presented. Results from very different kinds of methods using various astronomical objects – from supernovae to large-scale structure – are shown. There is a remarkable preference for m values around 0.3, but there are also some measurements that favour a higher or a smaller value.  相似文献   

17.
The ever-increasing pressure of producing at lower cost with higher quality and the competition, mainly from laser beam welding, are generating a number of new concepts of electron beam machines and electron beam generators. I would like to introduce to you some of these new developments.  相似文献   

18.
Knowledge of the elemental composition of the interstellar gas is of fundamental importance for understanding galactic chemical evolution. In addition to spectroscopic determinations of certain element abundance ratios, measurements of the composition of interstellar pickup ions and Anomalous Cosmic Rays (ACRs) have provided the principal means to obtain this critical information. Recent advances in our understanding of particle acceleration processes in the heliosphere and measurements by the Voyagers of the energy spectra and composition of energetic particles in the heliosheath provide us with another means of determining the abundance of the neutral components of the local interstellar gas. Here we compare the composition at the termination shock of six elements obtained from measurements of (a) pickup ions at ~5 AU, (b) ACRs in the heliosphere at ~70 AU, and (c) energetic particles as well as (d) ACRs in the heliosheath at ~100 AU. We find consistency among these four sets of derived neutral abundances. The average interstellar neutral densities at the termination shock for H, N, O, Ne and Ar are found to be 0.055±0.021 cm?3, (1.44±0.45)×10?5 cm?3, (6.46±1.89)×10?5 cm?3, (8.5±3.3)×10?6 cm?3, and (1.08±0.49)×10?7 cm?3, respectively, assuming the He density is 0.0148±0.002 cm?3.  相似文献   

19.
China civil aviation is at present in a crucial time of reform and development, faced with major tasks of separating business operations from government administration, transferring the responsibilities of the administration, and the strategic regroup of enterprises. The rapid growth of the national economy lays a good foundation for China civil aviation. The economy globalization, the trade deregularization, and the regulation integration brought both the opportunity and the challenge to Chin…  相似文献   

20.
Photoelectric WBVR observations of Be star HDE 245770=V 725 Tau, the optical counterpart of the transient X-ray pulsar A0535+26, having a pulse period of about 104 s, were conducted for more than 10 years. An irregular long-term optical variability of the star with amplitudes of the order of a few tenths of magnitude was found to be a usual phenomenon. In some cases rapid changes of the star's optical luminosity with a characteristic period of a few tens of minutes or a few hours, and an amplitude of several hundredths of magnitude in all the spectral bands used, which have practically coincided or correlated with the X-ray pulsar outbursts detected by X-ray satellites, were observed.Photoelectric recording of the optical flux from HDE 245770 were made in 1981–1982 with a time resolution of 1 second and 10 s, respectively, in theR spectral band (0 7000 Å) and in the narrowH -emission-line band (1/2 75 Å) using a 48-cm reflector of High-Mountain Tien-Shan observatory of the Sternberg Astronomical Institute near Alma-Ata. An analysis of autocorrelation functions of the flux changes from object under study and a comparison with the star BD+26° 876 indicated the variability of luminosity of V 725 Tau in theR spectral band on a time scale of a few tens of second; this variability resembles shot noise with a characteristic time of stochastic bursts of about 15–20 s and their amplitudes of about a few tenths of a percent. InH -emission-line radiation autocorrelation functions and power spectra show quasiperiodic variability of luminosity of HDE 245770 with a characteristic period of about 100–150 s and an amplitude in the neighbour-hood of 0.5%. The latter result is not quite reliable because of not quite fine weather conditions during the observations; independent observations and check-up are required.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号