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1.
Decelerated motion of 12 coronal eruptions is studied. It is found that the measured decelerations and deceleration rates depend on the events' plane-of-sky velocities and heights. The dependence of deceleration on the velocity is described better by a quadratic function then by linear fit. Results are interpreted in terms of a viscous drag. An empirical relation expressing the decrease of the drag effectiveness with the projected height is established. The interplay between the Lorentz force, viscous drag, and gravity is discussed. Several examples are considered to illustrate the relative contributions of these forces under various circumstances. 相似文献
2.
Dušan Polomčić Bojan Hajdin Zoran Stevanović Dragoljub Bajić Katarina Hajdin 《Hydrogeology Journal》2013,21(7):1519-1530
The Vi? Bare groundwater source is used to supply water to the population and industry of Obrenovac, one of the municipalities of Belgrade (the capital of Serbia). It is a typical riverbank filtration site; exploitation is performed through 30 drilled wells and two radial wells located in the meander of the Sava River. The established hydraulic connection between the river and tapped aquifer is so great that the river regime has a dominant influence on the aquifer. As a consequence of this, water-delivery reduction occurs in the dry months (summer–autumn), when the population needs water the most. Based on the data associated with the river’s gauges, precipitation, quantity of pumped water and groundwater-level fluctuation, a simulation of the groundwater regime for non-steady-state flow conditions has been undertaken through a numerical model. To overcome problems of water shortage during the dry season, the possibility of artificial recharge using an infiltration channel, made up of two connected parts, was analyzed. During the dry months, 80 % of the wells receive water partly from the infiltration channel. In this way, possibilities for extracting additional water are created. The application of this concept is discussed. 相似文献
3.
Longitude–latitude grids are commonly used for surface analyses and data storage in GIS. For volumetric analyses, three‐dimensional meshes perpendicularly raised above or below the gridded surface are applied. Since grids and meshes are defined with geographic coordinates, they are not equal area or volume due to convergence of the meridians and radii. This article compiles and presents known geodetic considerations and relevant formulae needed for longitude–latitude grid and mesh analyses in GIS. The effect of neglecting these considerations is demonstrated on area and volume calculations of ecological marine units. 相似文献
4.
We present a statistical study of the characteristics of type-II radio bursts observed in the metric (m) and deca-hectometer
(DH) wavelength range during 1997–2008. The collected events are divided into two groups: Group I contains the events of m-type-II
bursts with starting frequency ≥ 100 MHz, and group II contains the events with starting frequency of m-type-II radio bursts
< 100 MHz. We have analyzed both samples considering three different aspects: i) statistical properties of type-II bursts, ii) statistical properties of flares and CMEs associated with type-II bursts, and iii) time delays between type-II bursts, flares, and CMEs. We find significant differences in the properties of m-type-II bursts
in duration, bandwidth, drift rate, shock speed and delay between m- and DH-type-II bursts. From the timing analysis we found
that the majority of m-type-II bursts in both groups occur during the flare impulsive phase. On the other hand, the DH-type-II
bursts in both groups occur during the decaying phase of the associated flares. Almost all m-DH-type-II bursts are found to
be associated with CMEs. Our results indicate that there are two kinds of shock in which group I (high frequency) m-type-II
bursts seem to be ignited by flares whereas group II (low frequency) m-type-II bursts are CME-driven. 相似文献
5.
We present a simple method of forecasting the geomagnetic storms caused by high-speed streams (HSSs) in the solar wind. The
method is based on the empirical correlation between the coronal hole area/position and the value of the Dst index, which is established in a period of low interplanetary coronal mass ejection (ICME) activity. On average, the highest
geomagnetic activity, i.e., the minimum in Dst, occurs four days after a low-latitude coronal hole (CH) crosses the central meridian. The amplitude of the Dst dip is correlated with the CH area and depends on the magnetic polarity of the CH due to the Russell – McPherron effect.
The Dst variation may be predicted by employing the expression Dst(t)=(−65±25×cos λ)[A(t
*)]0.5, where A(t
*) is the fractional CH area measured in the central-meridian slice [−10°,10°] of the solar disc, λ is the ecliptic longitude of the Earth, ± stands for positive/negative CH polarity, and t−t
*=4 days. In periods of low ICME activity, the proposed expression provides forecasting of the amplitude of the HSS-associated
Dst dip to an accuracy of ≈30%. However, the time of occurrence of the Dst minimum cannot be predicted to better than ±2 days, and consequently, the overall mean relative difference between the observed
and calculated daily values of Dst ranges around 50%. 相似文献
6.
Tatiana Pertuz Alireza Malehmir Jordan Bos Bojan Brodic Yinshuai Ding Richard de Kunder Paul Marsden 《Geophysical Prospecting》2022,70(1):79-94
A prototype electromagnetic vibrator, referred to here as E-Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E-Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two-dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E-Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E-Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E-Vib source for improved targeting in hardrock geological settings. 相似文献
7.
8.
In this report, we present the situation in Slovenia, Europe with regard to natural hazards, emphasizing land-sliding problems.
Furthermore, we shortly present the University of Ljubljana and the Faculty of Civil and Geodetic Engineering as the new member
of the ICL that was selected to be the World Center of Excellence on Landslide Risk Reduction for the period of 2008–2013
with the project entitled “Mechanisms of landslides in over-consolidated clays and flysch” in the Activity scale and targeted
region as “National.” Some preliminary results of this project are shortly presented at the end. 相似文献
9.
Planning Geotechnical Investigation Using ANFIS 总被引:2,自引:2,他引:0
Bojan Žlender Primož Jelušič Djamalddine Boumezerane 《Geotechnical and Geological Engineering》2012,30(4):975-989
Engineering experience may be written in mathematical form by using adaptive network-based fuzzy inference system (ANFIS). In this article we propose a method to use engineering experience and build a model, which can be used as a systematic decision support tool for engineers dealing with new problems. Planning geotechnical investigations is based on experience, which are used to obtain optimal number of investigation points, field and laboratory tests. To achieve this objective we define minimum number of investigation points and several input parameters which could increase or decrease the number of investigation points. The expert’s evaluations were put in a table, from which we generate the basis of the system. The paper presents a concept for planning geotechnical investigation for buildings using ANFIS and practical examples show its usefulness. 相似文献
10.
We examined the occurrence of marine debris in the gastrointestinal tract of 54 loggerhead sea turtles (Caretta caretta) found stranded or incidentally captured dead by fisheries in the Adriatic Sea, with a curved carapace length of 25.0-79.2 cm. Marine debris was present in 35.2% of turtles and included soft plastic, ropes, Styrofoam and monofilament lines found in 68.4%, 42.1%, 15.8% and 5.3% of loggerheads that have ingested debris, respectively. The dry mass of debris per turtle was low, ranging from <0.01 to 0.71 g, and the ingestion was not significantly affected by sex or body size (all p > 0.05). Marine debris averaged 2.2 ± 8.0% of dry mass of gut content, with a maximum of 35% found in a juvenile turtle that most likely died due to debris ingestion. Considering the relatively high occurrence of debris intake and possible sub-lethal effects of even small quantities of marine debris, this can be an additional factor of concern for loggerheads in the Adriatic Sea. 相似文献