大气紊流数字仿真的改进方法

赵震炎等提出了一种数字摸拟Dryden大气紊流的方法。该方法使用方便,并具有一定的理论基础。但是在某些步长情况下它的相关函数和Dryden模型的理论值吻合得还不够令人满意。本文从理论上分析了产生误差的原因,并且提出了改进的方法。通过相关性检验可以看到改进后的仿真结果非常符合Dryden谱的大气紊流模型。     

日地共转扰动似稳结构及其反相和漂移规律的最新证据

日地共转扰动似稳结构及其反相现象在第２１及２２周再次显现，从而证实了上述发现是一种在长达世记的时间尺度内存在的普遍规律。包括１９９１－１９９２年内的百年地磁扰动资料还说明偶数太阳周的共转似稳结构扰动峰有逆太阳自转而线性性漂移的趋向。对即将来临的极小年前可能出现的共转扰动作了试验性的预测。     

自抗扰技术在船载天线伺服系统中的应用研究

为减小船摇扰动对船载天线伺服系统指向及跟踪精度的影响，引入线性自抗扰控制器（LADRC）对伺服系统位置环进行改进。首先对天线伺服系统模型进行简要分析，建立系统状态空间方程；然后利用LADRC对系统进行改进，并对其参数设计进行了详细介绍，同时为提高系统动态跟踪性能，利用TD微分器提取目标速度信息进行前馈补偿；最后经实验测试验证，LADRC相对于传统PID控制器能够保持天线伺服系统动态性能不下降，同时有效提高系统的抗船摇性能。     

Multi-input multi-output random vibration control using Tikhonov filter

Noises always disturb the control effect of an environment test especially in multi-input multi-output (MIMO) systems. If the frequency response function matrices are ill-conditioned, the noises in the driving forces will be amplified and the response spectral lines may awfully exceed their tolerances. Most of the major biases between the response spectra and the reference spectra are pro-duced by the amplified noises. However, ordinary control algorithms can hardly reduce the level of noises. The influences of the noises on both the auto-and cross-power spectra are analyzed in this paper. As a conventional frequency domain method on the inverse problem, the Tikhonov filter is adopted in the environment test to suppress the exceeding spectral lines. By altering regularization parameters gradually, the auto-power spectra can be improved in a closed control loop. Instead of using the traditional way of selecting regularization parameters, we observe the coherence change to estimate noise eliminations. Incidentally, the requirement of coherence control can be realized. The errors of the phase are then studied and a phase control algorithm is introduced at the end as a sup-plement of cross-power spectra control. The Tikhonov filter and the proposed phase control algo-rithm are tested numerically and experimentally. The results show that the noises in the vicinity of lightly damped resonant peaks are more stubborn. The response spectra are able to be greatly improved by the combination of these two methods.     

A novel environmental control system based on membrane dehumidification

This paper conducts a simulation study of a novel aircraft environmental control system based on membrane dehumidification(MD-ECS),and compares the system with the up-to-date four-wheel high pressure de-water system(4WHPDW-ECS).Mathematical models for the two systems are established,and a system simulation using a numerical technique is performed to analyze and compare the cooling performance of the two systems.Simulation results show that the cooling capacity of MD-ECS is much higher than that of 4WHPDW-ECS under the same working conditions,indicating that the novel system is theoretically feasible and promising.The effects of the sweep ratio of the membrane dehumidifier on the dehumidification and cooling performance of the system is also investigated.     

直升机机内PWM照明调光系统产生音频干扰问题的研究

在直升机机内照明调光领域，国外军机已广泛采用脉冲宽度调制（PWM）调光方式。PWM调光方式相比传统线性调光方式具有以下明显优点：效率高，调光范围宽，功耗小，带载能力强，附加损耗小等。但PWM调光系统的不足是电磁辐射，尤其会对机内通话系统产生音频干扰，在机通耳机中会出现明显干扰声，影响机内通话质量。本方案能有效抑制PWM...     

Saw-tooth substorms: Inconsistency of repetitive bay-like magnetic disturbances with behavior of aurora

The relationships between the magnetic disturbance onsets, aurora dynamics and particles injections at the geostationary orbit have been analyzed in detail for 25 sawtooth substorms. It is shown that inconsistency between the above signatures of the substorms onset is typical of the powerful sawtooth substorms, unlike the isolated (“classical”) magnetospheric substorms. The distinguishing feature of the aurora in case of saw-tooth substorms is permanently high level of auroral activity irrespective of the magnetic disturbance onsets and the double oval structure of the aurora display. The close relationship between the aurora behavior and the particle injections at geostationary orbit is also broken. The conclusion is made, that the classical concept of the substorm development, put forward by Akasofu (1964) for isolated substorms, is not workable in cases of the sawtooth disturbances, when the powerful solar wind energy pumping into the magnetosphere provides a permanent powerful aurora particle precipitation into the auroral zone.     

Effects of sector structure of the interplanetary magnetic field on the upper mesosphere–lower thermosphere dynamics

In this paper we study the influence of the interplanetary magnetic field (IMF) polarity changes caused by the Earth passing through the IMF sector boundary on the dynamic processes taking place in neutral atmosphere within the altitude interval of the upper mesosphere–lower thermosphere (83–101 km). The analysis has revealed the influence of the IMF sector structure on dynamics of the upper mesosphere–lower thermosphere. There has been a significant seasonal variation of the wind reaction to the IMF polarity changes observed. The influence of the IMF polarity changes on neutral atmosphere dynamics within the altitude range of 83–101 km is most pronounced in the zonal component of neural wind when the IMF polarity changes from negative to positive in all the seasons except for spring and when IMF polarity changes from positive to negative – in spring only.     

Extraterrestrial environmental impact assessments – A foreseeable prerequisite for wise decisions regarding outer space exploration,research and development

Although existing international instruments such as the Outer Space Treaty and Moon Agreement generally express sentiments for minimizing missions' extraterrestrial environmental impacts, they tend to be limited in scope, vague and generally unenforceable. There is no formal structure for assessing how and to what extent we affect those environments, no opportunity for public participation, no uniform protocol for documenting and registering the effects of our actions and no requirement to mitigate adverse impacts or take them into consideration in the decision-making process. Except for precautions limiting forward biological contamination and issues related to Earth satellites, environmental impact analysis, when done at all, remains focused on how missions affect the Earth and near-Earth environments, not how our actions affect the Moon, Mars, Europa, comets and other potential destinations. Extraterrestrial environmental impacts are potentially counterproductive to future space exploration, exploitation and scientific investigations. Clear, consistent and effective international protocols guiding a process for assessing such impacts are warranted. While instruments such as the US National Environmental Policy Act provide legally tested and efficient regulatory models that can guide impact assessment here on Earth, statutory legal frameworks may not work as well in the international environment of outer space. A proposal for industry-driven standards and an environmental code of conduct based, in part, on best management practices are offered for consideration.     

浅谈环境会计核算方法

生态环境的恶化使环境保护问题日益受到关注,各国不断加强对环境会计核算体系的研究,并取得一定的成果。但是,在我国有关环境会计核算的理论和实务研究尚处于起步阶段。本文从环境会计的内涵着手,对企业环境会计事项包含的内容,以及大循环成本理论下的账户设置进行了较为深入的探讨和研究。以期能对我国相关会计准则的建设、提高环境会计信息的可比性有所助益。