This article reports a method for forecasting an earthquake by synchronous anomalies of optical astronomic time-latitude residuals. The so-called optical astronomic time-latitude residuals for a certain astrometric instrument are the rest after deducting the effects of Earth whole motion from the astronomical time and latitude observations determined by the instrument. Forecasting practice for four earthquakes around the Yunnan Observatory occurring after 2010 shows that it does not generate false forecasts, and also does not miss forecasts of major earthquakes. This forecasting practice proves that the synchronous anomalies of astronomical time-latitude residuals can provide effective warning sign for earthquake occurrence around observatory station, thus deserves attention and further study. and Su Youjin, Gao Yuping, Hu Hui.
Purification of quartz using an environment-friendly method is important in the contaminants removal. This paper presents advanced method based on calcination pretreatment combined with ultrasound-assisted leaching, for removing iron impurities from industrial quartz. The solvent used is a mixture comprised by diluted hydrochloric acid and oxalic acid. The effects of experimental parameters were investigated and the purification mechanism was discussed using particle size analyzer, scanning electron microscope and polarized light microscope. SiO2 content of concentrate could be increased from 99.6828% to 99.9047%, which achieved 3N level high purity quartz, and Fe2O3 content reduced from 0.0857% to 0.0223%, under the optimal conditions, i.e., calcination temperature of 900 °C, holding time of 2 h, oxalic acid concentration of 10 g/L, hydrochloric acid concentration of 5%, liquid solid ratio of 5, leaching temperature of 60 °C, ultrasound power of 400 W and treatment time of 30 min. Compared to conventional method, the proposed method significantly accelerates the leaching process and increases the iron removal rate. At the same time, the method also can remove gas-liquid inclusions. and Yang Changqiao, Li Suqin, Bai Jiaxing, Han Shuaishuai.
The velocities of the Global Positioning System (GPS) stations are widely employed for numerous geodynamical studies. The aim of this paper is to investigate the reliability of station velocities and to draw reader’s attention that for proper estimates of velocity, we need to consider the optimal character of noise. We focus on a set of 115 European GPS stations which contributed to the newest release of the International Terrestrial Reference Frame (ITRF), i.e. ITRF2014. Based on stacked Power Spectral Densities (PSDs), we show that amplitudes o f seasonal signals are significant for nine harmonics of tropical year (365.25 days) and two harmonics of draconitic year (351.60 days). The amplitudes of tropical annual signal fall between 0.1-8.4 mm and are much higher for vertical component than for horizontal. Draconitic annual signal reaches the maximum amplitudes of 1.2 and 0.9 mm for North and East, respectively, whereas is slightly higher for the Up component with a maximum of 3.1 mm. We performed a noise analysis with Maximum Like lihood Estimation (MLE) and found that stations in Central and Northern Europe are characterized by spectral index between flicker and random-walk noise, while stations in Southern and Western Europe: between white and flicker noise. Both amplitudes and spectral indices of power-law noise show a spatial correlation for Up component. We compared the uncertainties of velocities derived in this study with a combination of power-law and white noises to the ones offici ally released in the ITRF2014 with a pure white noise. A ratio of the two estimates is larger than 10 for 13 % and 30 % of stations in horizontal and vertical direction, respectively with medians of 6 and 7. The large differences support the fact that at the velocity determination the proper noise characteristic should be taken into account to avoid any mislead interpretation., Anna Klos and Janusz Bogusz., and Obsahuje bibliografické odkazy
In the general tropospheric tomography model, the tomographic area is divided into a large number of voxels, which provides convenience for reconstructing tomographic observation equations. However, due to the defect of GNSS acquisition geometry, there are plenty of empty voxels for any tomographic epoch. Moreover, an unreasonable assumption that water vapor density is constant within a voxel was imposed on the tomographic model. In this study, we proposed an improved method based on the dynamic node parameterized algorithm to solve both key problems. The proposed approach first tries to select effective GNSS signals and determines the dynamic scope of the tomographic area using the dynamic algorithm. The parameterization of the tomography model is performed by a cubic spline formula and Gauss weighted function. Additionally, a piecewise linear fitting method based on Newton-Cotes interpolation is introduced to estimate the tomographic observation of slant water vapor (SWV). The experimental results show that the average number of effective signals increased by 32.33 % and the mean RMSE of the tomographic results is decreased by 45 % with the proposed method. Further, compared with the tomographic results of the general method, the improved solutions have a more centralized distribution and a smaller bias., Wenyuan Zhang, Shubi Zhang, Nan Ding and Pengxu Ma., and Obsahuje bibliografii
Water is one of the most important components of the environment, having a direct effect on the maintenance of life on the Earth. In this paper, analysis of groundwater level variations, water balance and all the parameters included in these quantities, i.e. precipitation, evapotranspiration, surface run-off and subsurface run-off, were performed in the area of the Sudety Mountains for the period of November 2002 - October 2015. The groundwater level variations were computed on the basis of the mean Terrestrial Water Storage (TWS) values determined from Gravity Recovery and Climate Experiment (GRACE) observations and Global Land Data Assimilation System (GLD AS). TWS data have been determined with a spatial resolution of one degree and temporal resolution of one month. According to the results, groundwater level variation can be approximately determined by water balance changes (with reverse sign). Specifically, for the Sudety area a high average stability of total water storage over the period of past 13 years and decline in groundwater level by about 13 cm (approximately 1 cm/year) was detected., Zofia Rzepecka, Monika Birylo, Joanna Kuczynska-Siehien, Jolanta Nastula and Katarzyna Pajak., and Obsahuje bibliografické odkazy
High temperature alters the internal microstructure of rocks and consequently changes the physical and mechanical properties of rocks. Many studies have been carried out to examine the transformations in the microstructures of rocks under high temperature through near infrared spectroscopy (NIR), Raman spectroscopy, or thermo gravimetric analysis (TGA). The current review synthesizes the data from a number of literatures and summarizes the major transformations of silica rocks under high temperature. The analysis shows that silica rocks starts to lose the water adsorbed in open pores upon heating at about 150 °C. At 200-300 °C, the reaction between SiOH (silanole) in the rocks generates new Si-O-Si bonds as well as H2O, and decreases the open pores. The rocks undergo volume expansion at >550 °C, and the volume contracts and forms new micro pores or cracks which play an important role in the evacuation of the water., Jishi Geng, Qiang Sun, Yuchun Zhang and Yuliang Zhang., and Obsahuje bibliografické odkazy
Secondary deformations are ground movements occurring in areas of ceased underground mining. These are associated with delayed readjustment of rock mass resulting in subsidence, discontinuous deformations (sinks, cracks, etc.) due to destruction of underground, usually shallow, workings, and elevation of ground surface in response of rock mass to rising groundwater levels following the end of mine water drainage. Comparative analysis of secondary deformations in two former mining areas in the first period after cessation of underground hard coal mining is the subject of this study. We used ERS-1/2 and Envisat satellite radar interferometry data processed with PSInSAR technique and GIS to map vertical (in satellite’s line of sight, LOS) movements of the surface and analyse them in relation to location of coal fields and underground water table rise. In the study, two areas have been compared, the Ostrava city in the Czech part of the Upper Silesian Basin and the Wałbrzych Coal Basin in Poland. The results of analyses based on the results of PSInSAR processing between 1995 and 2000 for the Wałbrzych site indicate uplift (up to +12 mm/year) in closed parts of coal fields and subsidence (up to -8 mm/year) in areas of declining mining. Results of PSInSAR analysis over the Ostrava site indicate decaying subsidence after mine closures in the rate of up to -6 mm/year during 1995-2000. Residual subsidence and gentle uplift have been partly identified at surroundings of closed mines in Ostrava from 2003-2010 Envisat data. In Wałbrzych gentle elevation has been determined from 2002 to 2009 in areas previously subsiding. and Blachowski Jan, Jiránková Eva, Lazecký Milan, Kadlečík Pavel, Milczarek Wojciech.
The use of Continuously Operating Reference Stations, both singly and as part of an active network, is widely employed in surveying, engineering and other geomatics applications, achieving high accuracy positioning even in real time. With an active network the measurements of the reference stations are processed jointly in order to model the errors and compute network RTK corrections. Due to distance dependent errors (ionospheric and tropospheric delays), single base RTK positioning accuracy decreases with increased baseline length. However, the network solution (NRTK) retains the accuracy and the time to fix ambiguities (TTFA) at a constant level. This study aims to contribute to the scientific research on real time positioning based on active networks. In Southern Spain, ERGNSS, a national CORS network that provides GNSS data for post-processing and real time single- b ased reference station corrections, shares territory with the Andalusian Positioning Network (RAP), a local active network. RAP provides network an d single-based RTK corrections. In order to analyze the quality of real time positioning based on both networks, several tests have been performed on a sample of test points. The reference frame, the time to fix ambiguity resolution, precision, accuracy and repeatability of RTK positioning are considered as the evaluation parameters. The results confirm that the RAP network complements the precise positioning services provided by the ERGNSS network, ensuring accurate real time positioning, full cove rage and reliable positioning services in the Andalusian Community., Mª Selmira Garrido, Antonio J. Gil and Rafael Gaitán., and Obsahuje bibliografické odkazy