Equatorial Ionospheric Anomaly (EIA) and comparison with IRI model during descending phase of solar activity (2005–2009)

The ionospheric variability at equatorial and low latitude region is known to be extreme as compared to mid latitude region. In this study the ionospheric total electron content (TEC), is derived by analyzing dual frequency Global Positioning System (GPS) data recorded at two stations separated by 325 km near the Indian equatorial anomaly region, Varanasi (Geog latitude 25°, 16^/ N, longitude 82°, 59^/ E, Geomagnetic latitude 16°, 08^/ N) and Kanpur (Geog latitude 26°, 18^/ N, longitude 80°, 12^/ E, Geomagnetic latitude 17°, 18^/ N). Specifically, we studied monthly, seasonal and annual variations as well as solar and geomagnetic effects on the equatorial ionospheric anomaly (EIA) during the descending phase of solar activity from 2005 to 2009. It is found that the maximum TEC (EIA) near equatorial anomaly crest yield their maximum values during the equinox months and their minimum values during the summer. Using monthly averaged peak magnitude of TEC, a clear semi-annual variation is seen with two maxima occurring in both spring and autumn. Results also showed the presence of winter anomaly or seasonal anomaly in the EIA crest throughout the period 2005–2009 only except during the deep solar minimum year 2007–2008. The correlation analysis indicate that the variation of EIA crest is more affected by solar activity compared to geomagnetic activity with maximum dependence on the solar EUV flux, which is attributed to direct link of EUV flux on the formation of ionosphere and main agent of the ionization. The statistical mean occurrence of EIA crest in TEC during the year from 2005 to 2009 is found to around 12:54 LT hour and at 21.12° N geographic latitude. The crest of EIA shifts towards lower latitudes and the rate of shift of the crest latitude during this period is found to be 0.87° N/per year. The comparison between IRI models with observation during this period has been made and comparison is poor with increasing solar activity with maximum difference during the year 2005.     

Heavy ion observations by MARIE in cruise phase and Mars orbit

The charged particle spectrum for nuclei from protons to neon, (charge Z=10) was observed during the cruise phase and orbit around Mars by the MARIE charged particle spectrometer on the Odyssey spacecraft. The cruise data were taken between April 23, 2001 and mid-August 2001. The Mars orbit data were taken March 5, 2002 through May 2002 and are scheduled to continue until August 2004. Charge peaks are clearly separated for charges up to Z=10. Especially prominent are the carbon and oxygen peaks, with boron and nitrogen also clearly visible. Although heavy ions are much less abundant than protons in the cosmic ray environment, it is important to determine their abundances because their ionization energy losses (proportional to Z²) are far more dangerous to humans and to instruments. Thus the higher charged nuclei make a significant contribution to dose and dose equivalent received in space. Results of the charged particle spectrum measurements will be reported.     

快速大时间步长熵条件格式的分辨率研究

提出了高分辨率快速大时间步长熵条件格式的构造方法.用激波管问题对一族熵条件格式进行研究.在精度、步长、限制器方面进行了详细的数值实验,研究了同样计算量下各种格式的表现品质.从理论上保证了大时间步长格式的无振荡性质,从具体的数值实验分析中确定了大时间步长格式的分辨率问题.      

高超声速飞行器尾喷管的优化设计

以喷管上壁折转角、下壁长度、舵面长度及其折转角为设计变量,结合遗传算法和特征线法对高超声速飞行器尾喷管进行了优化设计,并对设计变量进行了参数研究.结果表明,所采用的优化设计方法计算效率高且比较准确,特别适合于高超声速飞行器尾喷管的优化设计;所采用的4个设计参数均能有效地影响尾喷管的气动性能,其中喷管上壁折转角和舵面折转角分别对喷管的升力和推力的影响相对明显,对其进行均衡选择方能得到最优的结果.      

Late cataractogenesis in primates and lagomorphs after exposure to particulate radiations.

Rhesus monkeys that were exposed in 1969, at the age of approximately 2 years, to low doses of "mixed-energy" protons (10- and 110-MeV) are exhibiting progressive (degenerative) lenticular changes. We have conducted regular examinations of this group of monkeys for cataractogenic development since 1987, i.e., 18 years after irradiation, and the animals began to show enhanced degrees of lenticular opacification two years later. The lenses of age-matched controls (median lifespan in captivity approximately 24 years) continue to exhibit much lower levels of opacification (senile cataracts). Trends in the new data are consistent with the cataractogenic patterns observed for other groups of monkeys that were exposed at similar ages in 1964 and 1965 to protons of different energies, and which we began to monitor only 20-21 years later. Therefore, the new information from the mixed-energy group of monkeys provides insight into the development of late cataractogenic sequelae in the other groups of animals during the 2-3 years before we began to measure them. Comparisons are also made here among recent results from the different groups of primates and from New Zealand white (NZW) rabbits that were exposed when young to 56Fe ions and monitored continuously thereafter. This is done because analogous expression of radiation-induced degenerative cataractogenesis also occurs late in the lifespan of the lagomorphs (control median lifespan in captivity approximately 5-7 years), but in this case the cataractogenic profile has been documented through most of the post-irradiation lifespan.     

Observational Constraints on Transport (and Mixing) in Pre-Main Sequence Disks

Currently available observational constraints on transport mechanisms in pre-main sequence disks are reviewed. The main observable quantity accessable by imaging the spatial structure of disks is the mass accretion rate, which constrains angular momentum transport, and migration and diffusion of disk material. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comments on "Bounds on Probability of Error in Decision Feedback Equalizers"

In the above paper1 a technique was proposed to derive an upper bound on the error probability of a decision feedback equalizer. It involves decomposition of the probability density function of residual intersymbol interference and derivation of Chebyshev-type bounds on the error functionals over the decomposed functions. In this correspondence, we demonstrate that the technique is not applicable in general. The result is not a bound in many cases.