Mesopause temperatures and relative densities at midlatitudes observed by the Mengcheng meteor radar

The atmospheric temperatures and densities in the mesosphere and lower thermosphere(MLT)region are essential for studying the dynamics and climate of the middle and upper atmosphere.In this study,we present more than 9 years of mesopause temperatures and relative densities estimated by using ambipolar diffusion coefficient measurements observed by the Mengcheng meteor radar(33.4°N,116.5°E).The intercomparison between the meteor radar and Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere by Broadband Emission Radiometry(TIMED/SABER)and Earth Observing System(EOS)Aura/Microwave Limb Sounder(MLS)observations indicates that the meteor radar temperatures and densities agree well with the simultaneous satellite measurements.Annual variations dominate the mesopause temperatures,with the maximum during winter and the minimum during summer.The mesopause relative densities also show annual variations,with strong maxima near the spring equinox and weak maxima before the winter solstice,and with a minimum during summer.In addition,the mesopause density exhibits a structure similar to that of the zonal wind:as the zonal wind flows eastward(westward),the mesopause density decreases(increases).At the same time,the meridional wind shows a structure similar to that of the mesopause temperature:as the meridional wind shows northward(southward)enhancements,the mesopause temperature increases(decreases).Simultaneous horizontal wind,temperature,and density observations provide multiple mesospheric parameters for investigating mesospheric dynamics and thermodynamic processes and have the potential to improve widely used empirical atmospheric models.

燃料元件行为分析程序METEOR1.5的校核

燃料元件性能分析程序对于核燃料研究、设计具有十分重要作用.本工作用国际原子能机构(IAEA)的合作项目--"高燃耗下燃料行为模型研究"(FUMEX-Ⅱ)中得出的燃料元件辐照试验数据对燃料元件行为分析程序METEOR1.5进行验证计算.计算结果表明,METEOR1.5程序在燃耗65GW·d/t(U)以内时,能够对轻水反应堆二氧化铀燃料辐照行为做出很好地预测.

Meteoric固态盘设计中的并行性策略研究

闪存(Flashmemory)作为存储介质已经过了多次技术变革,固态硬盘代替传统硬盘已成为了趋势.提出了一种新型固态盘设计体系结构:Meteoric结构,其并行性策略利用挖掘开关级、总线级、芯片级3个层次的并行性来充分提高访问闪存的并行性.针对并行闪存系统的时钟精度仿真结果表明:通过对照实验验证了并行性对于整体性能具有较大的提升.

An Alternative Explanation for a Screw-like Meteoric Train Photographed by Double-Station Observations

Two-station observation of meteors, especially a meteor trains, provides an effective approach to the measurement of the physical parameters. We have collected four special groups of photographs of meteoric trains taken at two stations during Leonids 2001. One representative group has been measured and analyzed in detail. An analysis has been reported in our first paper. In this paper, an alternative explanation for the screw-like meteoric train is suggested based on some physical calculations. The results reveal that this train has a screw-like structure and, apparently, spoke beams. The mother meteor of this train may be negatively charged and moves forward along a left-hand screw trajectory under the effect of the geomagnetic field. The spoke beams might be the visual effect of the long time exposure of many particles released from the disintegrated meteoroid.

Study of impact materials of akhnoor meteor crater in Jammu and Kashmir (India)

A sample of Akhnoor meteor crater, which fell on 2nd January 2009 in Jammu District, Jammu & Kashmir, India, has been analyzed for ele-mental composition by Spectroscopic tech-niques. Concentrations of 17 major, minor and trace elements were determined. The authentic-ity of the meteorite sample was established by comparing its composition with those of stan-dard meteorites/chondrite. The classification of the sample has been made by comparing the abundances and concentration ratios of ele-ments with other known meteorites.

Quasi-90-day oscillation observed in the MLT region at low latitudes from the Kunming meteor radar and SABER

Observations of a quasi-90-day oscillation in the mesosphere and lower thermosphere(MLT) region from April 2011 to December 2014 are presented in this study. There is clear evidence of a quasi-90-day oscillation in temperatures obtained from the Kunming meteor radar(25.6°N, 103.8°E) and Sounding of the Atmosphere using Broadband Emission Radiometry(SABER), as well as in wind observed by the Kunming meteor radar. The quasi-90-day oscillation appears to be a prominent feature in the temperatures and meridional wind tides and presents quite regular cycles that occur approximately twice per year. The amplitudes and phases of the quasi-90-day oscillation in the SABER temperature show a feature similar to that of upward-propagated diurnal tides, which have a vertical wavelength of ～20 km above 70 km. In the lower atmosphere, a similar 90-day variability is presented in the surface latent heat flux and correlates with the temperature in the MLT region. Similar to the quasi-90-day oscillation in temperature, a 90-day variability of ozone(O3) is also present in the MLT region and is considered to be driven by a similar variability in the upwardly-propagated diurnal tides generated in the lower atmosphere. Moreover, the 90-day variability in the absorption of ultraviolet(UV) radiation by daytime O3 in the MLT region is an in situ source of the quasi-90-day oscillation in the MLT temperature.

First results of optical meteor and meteor trail irregularity from simultaneous Sanya radar and video observations

Meteoroids entering the Earth's atmosphere can create meteor trail irregularity seriously disturbing the background ionosphere. Although numerous observations of meteor trail irregularities were performed with VHF/UHF coherent scatter radars in the past, no simultaneous radar and optical instruments were employed to investigate the characteristics of meteor trail irregularity and its corresponding meteoroid. By installing multiple video cameras near the Sanya VHF radar site, an observational campaign was conducted during the period from November 2016 to February 2017. A total of 242 optical meteors with simultaneous non-specular echoes backscattered from the plasma irregularities generated in the corresponding meteor trails were identified. A good agreement between the angular positions of non-specular echoes derived from the Sanya radar interferometer and those of optical meteors was found,validating that the radar system phase offsets have been properly calibrated. The results also verify the interferometry capability of Sanya radar for meteor trail irregularity observation. The non-specular echoes with simultaneous optical meteors were detected at magnetic aspect angles greater than ~78°. Based on the meteor visual magnitude estimated from the optical data, it was found that the radar nonspecular echoes corresponding to brighter meteors survived for longer duration. This could provide observational evidence for the significance of meteoroid mass on the duration of meteor trail irregularity. On the other hand, the simultaneous radar and video common-volume observations showed that there were some cases with optical meteors but without radar non-specular echoes. One possibility could be that some of the optical meteors appeared at extremely low altitudes where meteor trail irregularities rarely occur.

Characteristics of the quasi-16-day wave in the mesosphere and lower thermosphere region as revealed by meteor radar,Aura satellite,and MERRA2 reanalysis data from 2008 to 2017

This study presents an analysis of the quasi-16-day wave(Q16DW)at three stations in the middle latitudes by using a meteor radar chain in conjunction with Aura Microwave Limb Sounder temperature data and MERRA2(Modern-Era Retrospective Analysis for Research and Applications,Version 2)reanalysis data from 2008 to 2017.The radar chain consists of three meteor radar stations located at Mohe(MH,53.5°N,122.3°E),Beijing(BJ,40.3°N,116.2°E),and Wuhan(WH,30.5°N,114.6°E).The Q16DW wave exhibits similar seasonal variation in the neutral wind and temperature,and the Q16DW amplitude is generally strong during winter and weak around summer.The Q16DW at BJ was found to have secondary enhancement around September in the zonal wind,which is rarely reported at similar latitudes.The latitudinal variations of the Q16DW in the neutral wind and temperature are quite different.The Q16DW at BJ is the most prominent in both neutral wind components among the three stations and the Q16DW amplitudes at MH and WH are comparable,whereas the wave amplitude in temperature decreases with decreasing latitude.The quasi-geostrophic refractive index squared at the three stations in the period from 2008 to 2017 was revealed.The results indicate that the Q16DW in the mesosphere and lower thermosphere(MLT)at MH has a limited contribution from the lower atmosphere.Around March and October,the Q16DW in the troposphere at BJ can propagate upward into the MLT region,whereas at WH,the contribution to the Q16DW in the MLT region is largely from the mesosphere.

Seismic detections of the 15 February 2013 Chelyabinsk meteor from the dense Chin Array

ChinArray is a dense portable broadband seismic network to cover the entire continental China, and the Phase I is deployed along the north-south seismic belt in southwest China. In this study, we analyze seismic data recorded on the ChinArray following the February 15, 2013 Chelyabinsk （Russia） meteor. This was the largest known object entering the Earth＇s atmosphere since the 1908 Tunguska meteor. The seismic energy radiated from this event was recorded by seismic stations worldwide including the dense ChinAn＇ay that are more than 4000 km away. The weak signal from the meteor event was con- taminated by a magnitude 5.8 Tonga earthquake occur- red ~ 20 min earlier. To test the feasibility of detecting the weak seismic signals from the meteor event, we compute vespagram and perform F-K analysis to the surface-wave data. We identify a seismic phase with back azimuth （BAZ） of 329.7° and slowness of 34.73 s/deg, corre- sponding to the surface wave from the Russian meteor event （BAZ ） 325.97°）. The surface magnitude （Ms） of the meteor event is 3.94 ±0.18. We also perform similar analysis on the data from the broadband array F-net in Japan, and find the BAZ of the surface waves to be 316.61%. With the different BAZs of ChinArray and F-net, we locate the Russian meteor event at 58.80°N, 58.72°E. The relatively large mislocation （-438 km as compared with 55.15°N. 61.41°E by others） may be a result of theweak signals at teleseismic distances.

VHF meteor radar at King Sejong Station,Antarctica

Since 2002, we have been observing the mesosphere and lower thermosphere （MLT） region over King Sejong Station （KSS; 62.22°S, 58.78°W）, Antarctica, using various instruments such as the Spectral Airglow Temperature Imager （SATI）, All Sky Camera （ASC） and VHF meteor radar. The meteor radar, installed in March 2007, continuously measures neutral winds in the alti- tude region 70-110 km and neutral temperature near the mesopause 24 h.d-1, regardless of weather conditions. In this study, we present results of an analysis of the neutral wind data for gravity wave activity over the tip of the Antarctic Peninsula, where such activity is known to be very high. Also presented is temperature estimation from measurement of the decay times of meteor trails, which is compared with other temperature measurements from SATI and the Sounding of the Atmosphere using Broadband Emis- sion Radiometry （SABER） instrument onboard the Thermosphere Ionosphere Mesosphere Energy and Dynamics （TIMED） satel- lite.

Facies character and geochemical signature in the late Quaternary meteoric diagenetic carbonate succession at the Xisha Islands,South China Sea

The late Quaternary shallow-water carbonates have been altered by a variety of diagenetic processes,and further influenced by high-amplitude global and regional sea level changes.This study utilizes a new borehole drilled on the Yongxing Island,Xisha Islands to investigate meteoric diagenetic alteration in the late Quaternary shallowwater carbonates.Petrographic,mineralogical,stable isotopic and elemental data provide new insights into the meteoric diagenetic processes of the reef limestone.The results show the variation in the distribution of aragonite,high-Mg calcite(HMC)and low-Mg calcite(LMC)divides the shallow-water carbonates in Core SSZK1 into three intervals,which are UnitⅠ(31.20-55.92 m,LMC),UnitⅡ(18.39-31.20 m,aragonite and LMC)and UnitⅢ(upper 18.39 m of core,aragonite,LMC and HMC).Various degrees of meteoric diagenesis exist in the identified three units.The lowermost UnitⅠhas suffered almost complete freshwater diagenesis,whereas the overlying UnitsⅡandⅢhave undergone incompletely meteoric diagenesis.The amount of time that limestone has been in the freshwater diagenetic environment has the largest impact on the degree of meteoric diagenesis.Approximately four intact facies/water depth cycles are recognized.The cumulative depletion of elements such as strontium(Sr),sodium(Na)and sulphur(S)caused by duplicated meteoric diagenesis in the older reef sequences are distinguished from the younger reef sequences.This study provides a new record of meteoric diagenesis,which is well reflected by whole-rock mineralogy and geochemistry.

A comparison of MLT wind between meteor radar chain data and SDWACCM results

A meteor radar chain located along the 120°E meridian in the Northern Hemisphere from low to middle latitudes provides longterm horizontal wind observations of the mesosphere and lower thermosphere(MLT)region.In this study,we report a seasonal variation and its latitudinal feature in the horizontal mean wind in the MLT region observed by six meteor radar instruments located at Mohe(53.5°N,122.3°E),Beijing(40.3°N,116.2°E),Mengcheng(33.4°N,116.5°E),Wuhan(30.6°N,114.4°E),Kunming(25.6°N,108.3°E),and Fuke(19.5°N,109.1°E)stations.In addition,we compare the wind in the MLT region measured by the meteor radar stations with those simulated by the Whole Atmosphere Community Climate Model(WACCM).In general,the WACCM appears to capture well the seasonal and latitudinal variations in the zonal wind component.In particular,the temporal evolution of the eastward zonal wind maximum shifts from July to May as the latitude decreases.However,the simulated WACCM meridional wind exhibits differences from the meteor radar observations.

The Third Peak of the 1998 Leonid Meteor Shower

The Leonid meteor shower in November 1998 was observed widely by astronomers. The first peak, rich in bright meteors, appeared about 16 hours before the predicted maximum of the main shower. The main shower was also observed by both optical and radio methods during 19:00-21:00 UT on Nov. 17, and the radio peak was over 2500h-1. About 18 hours after the main shower, an abnormal phenomenon in the ionosphere was detected by two separate ionosphere observing stations. And the very high abnormal phenomenon maintained over one hour. The phenomenon showed that the ionosphere was injected with a large amount of small dust particles that could not be observed in optical and radio. The Observational results show that the Leonid meteor shower in 1998 had three peaks.

瑞舒伐他汀对低危的亚临床型动脉粥样硬化个体颈动脉内膜中层厚度进展的影响:METEOR试验

背景:动脉粥样硬化常在症状出现前已较严重,目前尚不清楚治疗对于Framingham风险评分(FRS)较低的轻中度亚临床型动脉粥样硬化中年个体是否有益。目的:评估他汀类药物治疗2年能否延缓或逆转颈动脉内膜中层厚度(CIMT)的增加。设计、地点和参与者:2002年8月至2006年5月间在美国和欧洲的61个初级医疗中心进行一项随机、双盲、安慰剂对照研究M ETEO R(瑞舒伐他汀对颈动脉内膜中层厚度的疗效),共纳入984例个体,纳入标准为:年龄(平均年龄57岁)为其唯一的冠心病危险因素或10年FRS小于10%,CIM T中度增厚(1.2～3.5mm),

Some Aspects of the Diurnal and Semidiurnal Tidal Wind Field in Meteor Zone

The diurnal and semidiurnal tidal wind field variations in the altitudes between 80 and 100 km of the earth's atmosphere over a mid-latitude station are studied by means of the phases of the zonal and meridional wind measurements made at Atlanta (34 ° N, 84 ° W). The rotation of diurnal tidal wind vector is seen to be clockwise at lower heights (80-86 km), swinging between clockwise and anti-clockwise at intermediate heights (88-96 km) and anti-clockwise at higher heights (96-100 km). The senses of rotation of diurnal and semidiurnal tidal wind vectors are compared between the stations located in the same and opposite hemispheres. The results are consistent with the tidal theory in the case of Atlanta and Adelaide (35°S, 139 ° E) whereas in the case of other stations considered in the present study, they showed marked variations.

The Nippon/Norway Svalbard Meteor Radar: First results of small-scale structure observations

The Nippon/Norway Svalbard Meteor Radar(NSMR), has been in operation since March 2001. While primarily thought of as an instrument for examining mean wind, tidal and gravity wave neutral atmosphere dynamics in the upper mesosphere region, it is also possible to investigate spatial and temporal structure of temperature and windshear. Here, the radar itself is described followed by a presentation of these derived parameters.

MEGlobal公司选择陶氏METEOR^(TM)技术

陶氏化学公司近日宣布：EQUATE石化公司旗下全资子公司MEGlobal进行了严格评估和筛选,最终为其在美国墨西哥湾的乙二醇工厂选择了陶氏METEOR^（TM）环氧乙烷和乙二醇加工技术和METEOR（TM）EO-RETRO催化剂。据悉,该工厂是MEGlobal公司在美国的首个生产设施。＂

MP89,二十一世纪的巴黎地铁——MP89自动型将于1998年在METEOR线路上行驶

巴黎地铁1号线贯穿城市东西方向,它是首条接受MP89列车的线路。在RATP(巴黎独立运输公司)的项目中MP89将是21世纪地铁车辆的基础。由ROGER TALLON设计GEC ALSTHOM制造的MP89是铁路技术革新的最新产品。

A simulating experiment on the geochemical variation trend at the initial period of meteoric waters converting to underground waters and ore fluids

Experimental studies were undertaken on leaching of sedimentary rocks (dolomite and sandstone) and Hg, Sb ores by distilled water under the condition of a completely open system (room temperature and room pressure). The aim is to find whether the halogen elements or metal elements first enter the solution at the early stage of meteoric waters converting to groundwaters and ore fluids, and, at the same time, to understand how and when they enter distilled water solutions from the rocks. The experimental results have shown that F and Cl began to enter the fluids in the initial period of thirty days. With increasing leaching duration, the amounts of the elements that entered the fluids increased steadily. During the period from 120 days to 150 days the amounts increased more drastically, followed a slow increase. It is found that the capability of Cl entering the solutions is much greater than that of F. Hg and Sb were found not to have entered the solutions till 120 days later. During this period of time the pH value of the solutions began to drop. As for Hg and Sb ores, Hg and Sb began to enter the solutions on the 60th or 90th day, greatly ahead of schedule, but the two metallic elements in the rock samples began to enter the solutions 150 days later. Relatively speaking, Hg is more easily leached out than Sb from the rocks. In some rock samples, Sb could be detected in the solutions at the end of the experiment. However, Cu, Pb and Zn had not been detected in the leaching solutions from the beginning to the end of the experiment. In the whole leaching process the pH value of the solutions tend to decrease slowly from {7.1} at the beginning to {6.5} at the end. That is to say, in the interaction between pure water and rock the halogen elements in the rocks were preferentially leached out and then entered the fluids. With increasing water/rock reaction duration and amount of halogen-group elements in the solution and with decreasing pH value of the solution, some active metallic elements began to release in small amounts. This experimental result can explain the source and mechanism of volatile components and trace metals in underground waters. Meanwhile, as for those ore deposits produced by ore fluids derived from meteoric waters, the experimental result is also helpful to the understanding of the geochemical variation trend at the initial stage of conversion of meteoric waters to ore fluids.

2023年国外空空导弹发展动态研究

全面介绍了2023年国外空空导弹最新发展情况,重点论述了美国的AIM-9X、AIM-120、AIM-260、“远射”项目、模块化先进导弹、“突变”项目,欧洲的ASRAAM、IRIS-T、“流星”导弹和创新导弹技术,以及俄罗斯的RVV-MD2,日本的JNAAM,以色列的“天空之矛”,印度的“阿斯特拉”等空空导弹最新研制进展和试验情况,最后总结空空导弹的最新发展特点。