The position sensitive low energy detector on board the ZEBRA telescope

In order to improve the low energy capability (15 ÷ 150 KeV) of the balloon borne “ZEBRA” low energy gamma imaging telescope (150 KeV-20 MeV), a large area, high spectral resolution (5% at 60 KeV), low background detector has been designed and is now under development.It consists of two MultiWire Spectroscopic Proportional Counter (SPC), escape gated, that have a sensitive area of 6000 cm², and are placed above the large area array of sodiumiodide position sensitive elements.     

Evaluation of the STORM model storm-time corrections for middle latitude

This paper presents results from the Storm-Time Ionospheric Correction Model (STORM) validation for selected Northern and Southern Hemisphere middle latitude locations. The created database incorporated 65 strong-to-severe geomagnetic storms, which occurred within the period 1995–2007. This validation included data from some ionospheric stations (e.g., Pruhonice, El Arenosillo) that were not considered in the development or previous validations of the model. Hourly values of the F2 layer critical frequency, foF2, measured for 5–7 days during the main and recovery phases of each selected storm were compared with the predicted IRI 2007 foF2 with the STORM model option activated. To perform a detailed comparison between observed values, medians and predicted foF2 values the correlation coefficient, the root-mean-square error (RMSE), and the percentage improvement were calculated. Results of the comparative analysis show that the STORM model captures more effectively the negative phases of the summer ionospheric storms, while electron density enhancement during winter storms and the changeover of the different storm phases is reproduced with less accuracy. The STORM model corrections are less efficient for lower-middle latitudes and severe geomagnetic storms.     

Multi-Target Tracking in Clutter without Measurement Assignment

When tracking targets using radars and sonars, the number of targets and the origin of data is uncertain. Data may be false measurements or clutter, or they may be detections from an unknown number of targets whose possible trajectories and detection processes can only be described in a statistical manner. Optimal all-neighbor multi-target tracking (MTT) in clutter enumerates all possible joint measurement-to-track assignments and calculates the a posteriori probabilities of each of these joint assignments. The numerical complexity of this process is combinatorial in the number of tracks and the number of measurements. One of the key differences between most MTT algorithms is the manner in which they reduce the computational complexity of the joint measurement-to-track assignment process. We propose an alternative approach, using a form of soft assignment, that enables us to bypass this step entirely. Specifically, our approach treats possible detections of targets followed by other tracks as additional clutter measurements. It starts by approximating the a~priori probabilities of measurement origin. These probabilities are then used to modify the clutter spatial density at the location of the measurements. A suitable single target tracking (STT) filter then uses the modified clutter intensity for updating the track state. In effect, the STT filter is transformed into an MTT filter with a numerical complexity that is linear in the number of tracks and the number of measurements. Simulations show the effectiveness of this approach in a number of different multi-target scenarios.     

TC4钛合金纵弯超声振动铣削装置及其加工性能研究

TC4钛合金因其优异的综合机械性能在航空、航天工业中得到了广泛应用,但其高塑性和低导热系数引起的刀具–切屑黏附是制约其铣削加工性能提升的一个关键因素.针对TC4钛合金铣削加工性能提升的需求,提出了一种基于刀具纵弯复合超声振动辅助铣削的加工方式,通过控制刀具纵弯复合超声振动的幅值和相位实现可控的间歇式切削,降低刀具–切屑...     

假目标效应对弹道导弹突防概率的影响分析

文中论述了采用突防技术提高弹道导弹突防能力的重要性,阐述了诱饵假目标突防手段的特点和在弹道导弹突防系统中的作用,对采用假目标诱饵作为突防措施的一枚进攻导弹的突防概率给出了定量计算。     

少铝硝胺推进剂燃速调节研究

研究了多种添加剂对少铝RDX／HTPB推进剂燃速的影响，结果表明硼氢化合物、活性碳、碳氢化合物以及铁的化合物等均对燃速催化不明显，但Cat．3却能大幅度提高少铝RDX／HTPB推进剂的燃速，7．0MPa下燃速提高幅度近40％。     

What is the optimum solar proxy for long-term ionospheric investigations?

The problem of optimum solar proxy is important for long-term and/or climatological studies of ionospheric parameters. Here we focus on possibly different optimum solar proxies for different ionospheric parameters, as they are affected by partly different spectral ranges of solar ionizing radiation. We use yearly average values of foF2 and foE of four European stations with long (1976–2014) and high-quality data (Juliusruh, Pruhonice, Rome, Slough/Chilton), and the global total electron content (G-TEC). Four solar proxies are used: F10.7, Mg II, solar Lymna-alpha flux Fα and sunspot numbers. The most important finding is that the optimum solar proxies are different for different ionospheric parameters. The most suitable solar proxy for foF2 is found to be Mg II, whereas for foE F10.7 evidently outperforms Mg II. Fα and sunspot numbers perform slightly worse but none of four solar proxies performs poorly. F10.7 is favored for G-TEC, to some extent surprisingly, as previous results favored rather Mg II.     

跟随名士的步伐 黄酒凝香之绍兴 天涯海角之三亚

繁忙的都市生活让上人们没有一丝喘气的机会,这时候便会向往美丽的大自然甚至,想体验一下古人简单却又充实美满的生活历史上的风流名士大多是旅游爱好者,他们走南闯北留下了一篇篇美丽的文章,让后人敬仰的向往。这一次的假日,就跟着名士的步伐,静静地,在曾经俘获他们心灵的地方,小住几日吧。     

重现头顶的璀璨星空

作为一个常年混迹于网络的看客,相信近几年国内发生的诸多热点事件大家部不会错过,当潜规则被搬上桌面,成为心照不宣的秘密;当躲猫猫、俯卧撑、楼脆脆这些荒唐的事件接二连三地发生;当一个个"范跑跑"、"郭美美"越来越理直气壮地跳出来时,我们一边围观、谴责,又一边逃避着,这些事也层出不穷,竟成为常态。这个世界到底怎么了?一个接一个令人发指的荒唐事件的上演,短暂的警示后,却反成了人们茶余饭后的谈资,少有人会真正地去思考:我们生活的社会正在遭遇一场什么样的变故?近期有幸读了华中科技大学出版社策划出版的《中国刻不容缓——拯救我们的道德》一书,不说醍醐灌顶,却有如读了《警世钟》的感觉,国民的道德信念日渐式微,以陕西周老虎事件和河北三鹿     

期待意料之外的惊喜——阿联遒艾瓦迪悦榕庄

概况面对阿拉伯湾深蓝的海水和雄伟壮丽的Al Hajjar Mountains山景,这片绿洲可让您暂避尘世喧嚣。艾瓦迪悦榕庄是阿联酋首个提供全独立泳池别墅概念的沙漠度假村,拥有完备的设施,包括宽敞的全独立泳池别墅、源于亚洲的水疗spa设施、专属的自然保护区、私人海滩俱乐部及18洞锦标赛高尔夫球场。悦榕庄为城市居民提供一个独一无二的休闲体验,在度假村专属的自然保护区内,当地沙漠野生动物自由徜徉,另也备有精彩