一种定量建立主题数据库的算法

本文利用企业模型中的企业活动与实体之间的关系给出了实体组之间的相关系数定义，在此基础上，给出了实体组的分组算法，从而应可以根据主要数据库分划标准把实体划分成实体大组，形成主题数据库。     

论承包经营企业的短期行为及其对策

本文针对承包经营企业中的短期行为问题,列举了它的表现形式并对其成因进行了分析,在此基础上,提出了若干现实对策。     

仿生光磁导航技术发展研究综述

仿生导航是在仿生技术基础上发展起来的新型导航技术方法,该方法融合了仿生技术的优点,因其抗干扰性强、适应范围广的特点,迎来了研究的热潮。从仿生光流导航、仿生偏振光导航、仿生类脑导航和仿生地磁导航四个角度对近年来大量的相关文献进行了综合性地整理和分析,阐述了其导航原理、发展现状和动态,对其未来的发展前景进行了展望,指出了限制现有技术的难点和瓶颈,对未来仿生导航技术的发展提供了参考,有一定的指导作用。     

Comparison of observed ionospheric vertical TEC over the sea in Indian region with IRI-2016 model

The vertical ionospheric TEC values obtained from GAGAN grid based ionospheric delay correction values over the sea in the Indian equatorial region have been compared with the corresponding values derived from the International Reference Ionosphere model, IRI-2016. The objective of this work is to study the deviation of the vertical TEC derived from the IRI model from ground truths over the sea for different conditions. This will serve the basic intention of assessing the candidature of the IRI model as an alternative ionospheric correction model in navigation receivers in terms of accuracy. We have chosen different solar activity periods, seasons, geomagnetic conditions, locations etc. for our comparison and analysis. The TEC values by the IRI-2016 were compared with the actual measured values for the given conditions and errors were obtained. The measured vertical TEC values at the ionospheric grid points were derived from the GAGAN broadcast ionospheric delay data and used as reference. The IRI model with standard internal functions was used in estimating the TEC at the same ionospheric grid points. The errors in the model derived values are statistically analysed. Broadly, the results show that, for the Indian sector over the sea, the IRI model performs better on quiet days in off equatorial regions, particularly in the northern region. The overall performance degrades for other conditions with the model generally underestimating the true TEC values and most severely in the equatorial region. The performance is worst in this region for the disturbed days of the equinoctial period. The comparison study is also done with the TEC data measured directly by dual frequency GPS receivers. The results were found to be in general agreement with those obtained by comparing the model with GAGAN broadcast data as reference. This study will be useful in considering the IRI-2016 model for real time estimates of TEC as an alternative to the current parametric model in a satellite navigation receiver in absence of other options.     

Non-stationarity and cross-correlation effects in the MHD solar activity

The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously.     

Latitudinal distribution of solar coronal active regions

We studied the cyclic evolution of the latitudinal distribution of solar coronal active regions based on daily images from SOHO EIT for the period 1995–2017. Fully automated software was used, which included the following steps: initial preparation of images in the data series, normalization of histograms and correction of limb brightening, segmentation of images using threshold intensity values obtained from their histograms, scanning of segmented images in heliographic coordinates and obtaining profiles of latitudinal distribution of coronal active regions for each image of the data series. From the output data, we obtained a temporary change in the latitudinal distribution profiles and the migration of activity centers on the solar disk. From the period of minimum activity to the next minimum in both hemispheres, activity centers begin to migrate from high latitudes towards the equator. At the same time, the general center of activity repeatedly changes the direction of migration. The latitudinal distribution of the so-called presence factor of coronal active regions closely resembles the magnetic butterfly diagram, which proves their direct causal relationships. Variations in the presence factor of coronal active regions are correlated with cyclic variations in the sunspot daily numbers.     

How do interplanetary shock impact angles control the size of the geoeffective magnetosphere?

In this paper, we investigate temporal and spatial magnetosphere response to the impact of interplanetary (IP) shocks with different inclinations and speeds on the Earth’s magnetosphere. A data set with more than 500 IP shocks is used to identify positive sudden impulse (SI⁺) events as expressed by the SuperMAG partial ring current index. The SI⁺ rise time (RT), defined as the time interval between compression onset and maximum SI⁺ signature, is obtained for each event. We use RT and a model suggested by Takeuchi et al. (2002) to calculate the geoeffective magnetospheric distance (GMD) in the shock propagation direction as a function of shock impact angle and speed for each event. GMD is a generalization of the geoeffective magnetosphere length (GML) suggested by Takeuchi et al. (2002), defined from the subsolar point along the X line toward the tail. We estimate statistical GMD and GML values which are then reported for the first time. We also show that, similarly to well-known results for RT, the highest correlation coefficient for the GMD and impact angle is found for shocks with high speeds and small impact angles, and the faster and more frontal the shock, the smaller the GMD. This result indicates that the magnetospheric response depends heavily on shock impact angle. With these results, we argue that the prediction and forecasting of space weather events, such as those caused by coronal mass ejections, will not be accurately accomplished if the disturbances’ angles of impact are not considered as an important parameter within model and observation scheme capabilities.     

Statistical characteristics of low latitude Pc4s: Influence of solar wind and IMF parameters

Pc4 signatures for the year 2013, extracted from geomagnetic north–south and east–west components of induction coil magnetometer (LEMI 30) from low latitude station Desalpar (DSP), operated by Institute of Seismological Research (ISR), India have been investigated vis-à-vis the prevalent interplanetary parameters (IMF) as well as the geomagnetic activity indices. A clear dominance of Pc4-5 (467 events) over Pc3 (17 events) is observed. Local time variation of Pc4 shows a peak in the noon sector in both X and Y components. Our investigations show that the dominant peak frequency is 10 mHz at low latitude region. Correlations with solar wind and IMF parameters illustrate highest occurrence of Pc4 for a solar wind speed of 300–400 km/s and average IMF B field of 3–6 nT. The amplitude of Pc4s at DSP shows an increase with increasing solar wind speed, plasma density, solar wind dynamic pressure and average B field which is also reflected in the trend of frequency variation of these pulsations. We report that IMF clock angle at low latitude does not have influence on Pc4 occurrence. Based on the characteristics of these events, detected in latitudinally distributed stations from low and mid-latitudes from northern and southern hemisphere, we infer that modes were compressional, which could be driven by K-H instability or solar wind dynamic pressure, as compressional modes can propagate to low latitude with little attenuation.     

半个太阳活动周期内我国中纬地区上空电离层等效板厚的变化特征

本文用新乡(电离层400km对下点是:32.4°N,115.6°E)、重庆(电离层400km对下点是:27.2°N,108.7°E)接收日本同步卫星ETS-Ⅱ的信标资料,研究了我国中纬地区上空半个太阳活动周期内(1981—1985)电离层等效板厚的变化特征,得到了等效板厚日变化、季变化的二维和三维等值图。由付里叶分析和回归方法得出等效板厚日变化各谐波分量与太阳黑子数12个月滑动平均值之间存在弱的线性关系。同时指出在等效板厚日变化中,于当地时0400—0700LT存在一明显的黎明峰。并对出现这种峰的原因作了讨论。      

基于故障行为的惯导产品贮存寿命试验设计

以典型惯导产品加速度计贮存寿命评估为例,提出了一种基于故障行为模型的加速退化试验设计方法,解决了缺乏预试验数据情况下试验应力水平设计的问题。在通过对产品特性和主机理分析基础上,确定表征产品贮存寿命特征参数及试验应力,构建了考虑材料等分散性的加速度计故障行为模型,用以描述参数加速时变规律的特性。在试验应力最高水平确定的情况下,基于给定置信度和故障行为模型,以高应力水平下退化量的置信下限与低应力水平下退化量的置信上限不交叉为原则,采用基于仿真的加速退化试验设计方法,优化确定低应力和中间应力水平,从而设计给出试验剖面,并给出了加速退化试验方案优选流程,最终从备选方案集中确定加速度计试验最优方案。通过实际案例分析,验证了该方法的有效性。