网络环境中安全防御措施的研究

随着网络带宽增加和网络应用的日益丰富,网络受到频繁的攻击,这种攻击采用了结合病毒、蠕虫、后门等多种方式,本文详细分析了蠕虫病毒及木马、黑客对网络的侵入和威胁,提出了安全防御措施,并阐述了利用Windows2003提供的防火墙为网络构筑安全防线的方法,Internet连接防火墙可以有效地栏截对Windows2003服务器的非法入侵,防止非法远程主机对服务器的扫描,提高Windows2003服务器的安全性,如果在用Windows2003构造的虚拟路由器上启用此防火墙功能,能够对整个内部网络起到很好的保护作用.     

论清代前期统一的历史局限性

对于清代前期的统一，我们既要看到它的深远影响，也应指出其严重失误。诸如排斥汉族将帅参与边疆事务，在边疆某些地区滥施淫威，对蒙古及黄教政策的消极影响，虚边政策的危害，闭关自守政策的恶果等等，结果很快从“盛世”坠入“衰世”，内忧外患，纷至沓来，到清末时已是不可救药了。     

Modelling the Torques Affecting the Hipparcos Satellite

Reconstructed attitude data for the Hipparcos mission as obtained in the final stages of the data analysis for the published catalogue is used to derive detailed information on the dynamics of the satellite. Most elements of the inertia tensor of the satellite could be calibrated from the observed acceleration data, which are also used to reconstruct torques due to solar radiation and gravity gradient, and the magnetic moment of the satellite and it's interaction with the magnetic field surounding the Earth. The effects of the oblateness of the Earth on the gravity gradient are evaluated and shown to be negligable. The magnetic field model includes both the `main' and the `disturbance' fields. The remaining systematic effects in residual torques are most likely attributed to variations in the magnetic field that are local and are beyond the models used to describe it. The angular momentum vector for one of the gyros was reconstructed from the torque it asserted on the satellite while it was running in redundant mode. This revised version was published online in August 2006 with corrections to the Cover Date.     

差值法与比值法的误差修正效果比较研究及应用

差值法与比值法对不同测量系统的误差修正效果不一样。本文将两种方法的比较用一个比值来描述,并用推得的公式进行量化表示。在进一步的应用研究中,理论分析与实验数据相互印证,同时得到许多有益的结论,有助于全面掌握测量系统的误差来源,从而灵活选择各种修正方法以获得更加准确的测量结果。     

提高飞机舱盖玻璃的抗故障能力是满足视情维修目的的根本

介绍了国产各型飞机舱盖玻璃所用的材料并进行了性能比较;介绍了飞机舱盖玻璃的主要故障模式并分别给予了故障原因分析;提出了提高飞机舱盖玻璃的抗故障能力的方法。     

民用飞机乘客使用PED的适航要求分析

2013年欧美适航当局陆续宣布允许乘客在全飞行阶段使用便携式电子设备（Portable Electronic Device,简称PED）,包括处于飞行模式的手机、平板电脑、笔记本电脑等。与PED使用有关的适航条款经过半个多世纪的不断发展已日趋成熟。为了表明飞机在PED辐射的环境下仍然是适航的,飞机制造商需要向局方表明飞机对PED前门耦合和后门耦合干扰的符合性。     

处理机匣/压气机非定常相互作用分析

实验研究了三个不同槽数圆弧斜槽处理机匣对压气机气动性能的影响,实验结果显示,只有当处理槽数确定的处理机匣/压气机非定常相互作用频率锁定在压气机分离绕流流场非定常特征频率附近时,处理机匣才能展示出满意的扩稳能力.实验利用25孔总压耙测量压气机静子出口S3流面总压流场结构,测量结果表明,处理机匣/压气机非定常相互作用不但大幅度改善了压气机分离绕流流场结构,还影响了压气机总压升径向分布.      

The Responsibility of the Engineering School in the Continuing Education of the Engineer

Engineering schools have a responsibility to provide a science background upon which graduates may build to solve the across-the-discipline challenges of tomorrow. They cannot and should not train for solutions to today's problems. Schools must insure that their faculty continues its education beyond the Doctor's degree by means of workshops, professional meetings, and involvement in investigation and research. Individuals must, however, retain primary responsibility for investment of time, energy, and effort necessary to remain a productive member of the profession for their career.     

Testing the Stability of the Fine Structure Constant in the Laboratory

In this review we discuss the progress of the past decade in testing for a possible temporal variation of the fine structure constant α. Advances in atomic sample preparation, laser spectroscopy and optical frequency measurements led to rapid reduction of measurement uncertainties. Eventually laboratory tests became the most sensitive tool to detect a possible variation of α at the present epoch. We explain the methods and technologies that helped to make this possible.     

Morgan phenomenon unravels the mysteries of the Universe

We readily convince ourselves that most achievements can be credited to the construction of powerful jet engines, which enable a spaceship to escape gravity. The principle of jet propulsion seems to work perfectly; jet engines can accelerate a rocket up to an incredible speed of 11 km/sec. Looks like there is nothing left to desire. However, from the physical point of view, 11 km/sec is not such a large value compared, for instance, to the speed of light. Would it be possible to attain half of that speed using gas jets? Unfortunately, the answer is no. Nevertheless, that is not the end of the story. The purpose of this article is to show that it is still possible to use the same principle to remove limitations on attainable speed if instead of gas jets, we employ ultrafast electron beams. The basic idea of our construction was inspired by the paper by H. Morgan (ibid., vol. 13, pp. 5-10, 1998). In that article he experimentally refuted the common premise that nothing can go faster than light and gave some theoretical arguments supporting his experimental data. Although the nature and underlying principles of the Morgan phenomenon are yet to be understood, we can already start thinking of its practical applications     

直升机性能与RMS综合一体化设计的研究

本文根据以往直升机型号研制中存在的性能或图样设计与RMS分析设计脱节的问题,提出了实现性能与RMS综合一体化的技术方法,以期满足使用部门的要求,实现直升机RMS新的跨越。     

亚声速轴流压气机失速监测方法试验

为了研究轴流压气机失速先兆信号监测的有效算法,对亚声速轴流压气机试验台的孤立转子在不同转速下,从稳定工况到失速工况叶顶不同轴向位置进行了动态压力信号测量试验,采用自相关分析和方差分析算法对试验数据进行了对比分析。结果表明,该压气机为突尖型失速,在叶顶前缘附近能明显感受到失速先兆信号,自相关分析监测到失速先兆信号的时间明显早于方差分析,可更有效的达到失速预警的作用。     

家族承诺在家族企业管理中的修正

近年来,理论界对家族企业的研究方兴未艾,而对家族承诺的研究却显得有点过冷,至今仍未形成完整意义上的家族承诺理论.从家族企业的相关论题入手,构建一个经修正后的比较完善的家族承诺理论模型,为进一步对家族企业及家族企业管理的研究提供参考和借鉴.     

基于PSO_LS-SVM的装备研制费用预测研究

在简要介绍了粒子群优化算法基本原理的基础上,建立了基于POS_LS-SVM的装备研制费用预测模型,并应用实例进行了验证。结果表明,采用PSO_LS-SVM方法进行装备研制费用预测,得到的预测结果精度更高、计算速度更快。     

The evolution of the anomalous component of the cosmic rays during the Ulysses mission

We have studied the evolution of the anomalous cosmic ray component at ULYSSES using observations of the quiet time helium fluxes obtained with the COSPIN Low Energy Telescope during the years from launch in October 1990 to the latest data in 1994. Shown are preliminary results of measurements in the energy range from 4.0 to 19 MeV/n. Following the drop in solar activity in late 1991, the low energy cosmic ray helium flux started to increase and continue to rise until the end of 1993, signifying the appearance of the anomalous component at ULYSSES.     

Formation of the Cores of the Outer Planets

The formation of the giant planets seems to be best explained by accretion of planetesimals to form massive cores, which in the case of Jupiter and Saturn were able to capture nebular gas. However, the timescale for accretion of such cores has been a problem. Accretion in the outer solar system differs qualitatively from planetary growth in the terrestrial region, as the larger embryo masses and lower orbital velocities make bodies more subject to gravitational scattering. The planetesimal swarm in the outer nebula may be seeded by earlier-formed large bodies scattered from the region near the nebular “snow line”. Such a seed body can experience rapid runaway growth undisturbed by competitors; the style of growth is not oligarchy, but monarchy.     

Aging avionics: the problems and the challenges

Aging avionics have become a problem because aircraft are being kept in service far longer than the original plan. This paper discusses the four key problems of aging avionics: (1) determining the systems that are the high cost drivers in order to select those that should receive priority; (2) determining the requirements for the replacement; (3) identifying alternative technologies that will satisfy the requirements and are affordable; and (4) determining the funding required and acquiring the funding needed to replace the aging avionics. Challenges encountered in solving these problems include management and technical. The problem of aging avionics is not limited to a single aircraft, but occurs across all aircraft. Cost-effective modernization requires cutting horizontally across all aging aircraft, and coordination with the end users and the existing management structure. A key technical challenge is to select an architecture that is upgradeable since the funding limitations may ensure parts will become obsolete prior to the completion of a drawn-out production.     

A System for the Measurement of the Amazon

The System for the Vigilance of the Amazon (SIVAM) is a $1.4 billion dollar project of Brazil aimed at the development and deployment of a high-technology system-of-systems to perform monitoring, protection, and control of the land, air, and water resources of the Brazilian Amazon region. The primary challenge of the SIVAM project is to perform remote sensing and communications over a vast and undeveloped land area. The SIVAM network meets this challenge through an extensive network of Air Traffic Control/Surveillance Radars, Environmental Sensors, Communications Systems, Airborne Sensor Systems, and Coordination Centers. Now fully operational, the SIVAM system is the world's largest fully integrated remote monitoring system of the environment and provides critical information on a timely basis to the Brazilian government, law enforcement agencies, and to commercial, educational, and research groups.     

Short-Lived Radioactivities and the Birth of the sun

Now extinct short-lived radioactive isotopes were apparently extant in the early solar system. Their abundances can be inferred from isotopic effects in their daughter nuclei in primitive meteorites, and the deviation of these abundances from expectations from continuous galactic nucleosynthesis yields important information on the last nucleosynthetic events that contributed new nuclei to the solar system and on the general circumstances of the Sun's birth. In this paper we present a rudimentary model that attempts to reconcile the abundances of ten short-lived radioactivities in the early solar system. In broad outlines, the picture requires 1) that Type Ia supernovae maintained a steady ISM supply of ⁵³Mn and ¹⁴⁶Sm, 2) that the r-process events that slowly admixed new ¹⁰⁷Pd, ¹²⁹I, ¹⁸²Hf, and ²⁴⁴Pu nuclei to the solar system occurred over an interval of several hundred million years prior to solar system formation, and 3) that a massive star, by injecting only material outside its helium-exhausted core into the proto-solar nebula, contributed ²⁶Al, ³⁶Cl, ⁴¹Ca, ⁶⁰Fe, and ¹⁸²Hf no more than one million years prior to the Sun's birth. In this picture, the live ¹⁸²Hf present in the early solar system was not due to r-process production but rather to a fast s-process in helium or carbon burning shell in the massive star. We conclude with a possible chemical-memory explanation for the putative ⁵³Cr/⁵²Cr gradient in the solar system. This revised version was published online in June 2006 with corrections to the Cover Date.     

舰载机着舰进近速度超出预期的影响因素研究

舰载机进近速度过大不仅会缩短机体疲劳寿命,而且会增加事故风险。通过分析得出,造成进近速度超出预期值的原因是飞行员为保证飞机沿固定下滑道下滑而对飞机的状态作出了调整。进一步分析得出,甲板风高于测试值是迫使飞机状态改变的直接因素,并利用统计数据分析验证了该结论的正确性;分析结果表明,甲板风增大的80%转化为进近速度的增加;提出以抬高基准角的方式应对大甲板风带来的进近速度的增加,以保证着舰安全。研究结论可应用于岸基模拟着舰训练中,可提高模拟训练和实际着舰的相似度,增强训练效果。