The dynamic recrystallization(DRX) and texture development, taking place during hot deformation of magnesium alloy AZ31 with a strong wire texture, were studied in compression at 673 K (0.73 Tm). Two kinds of samples ...The dynamic recrystallization(DRX) and texture development, taking place during hot deformation of magnesium alloy AZ31 with a strong wire texture, were studied in compression at 673 K (0.73 Tm). Two kinds of samples were machined parallelly to the extruded and transverse directions of Mg alloy rods. New fine grains are evolved at original grain boundaries corrugated at low strains and develop rapidly in the medium range of strain, finally leading to a roughly full evolution of equiaxial fine grains. Kink bands are evolved at grain boundaries corrugated and also frequently in grain interiors at low strains. The boundary misorientations of kink band increase rapidly with increasing strain and approach a saturation value in high strain. The average size of the regions fragmented by kink band is almost the same as that of new grains evolved in high strain. These characteristics of new grain evolution process are not changed by the orientation of the samples, while the flow behaviors clearly depend on it. It is concluded that new grain evolution can be controlled by a deformation-induced continuous reaction, i.e. continuous dynamic recrystallization(DRX). The latter is discussed by comparing with conventional, i.e. discontinuous DRX.展开更多
Annealing behaviors of hot-deformed magnesium alloy AZ31 were studied at temperatures from 300 to 673 K by optical and SEM/EBSD metallographic observation. Temperature dependence of the average grain size(D) is catego...Annealing behaviors of hot-deformed magnesium alloy AZ31 were studied at temperatures from 300 to 673 K by optical and SEM/EBSD metallographic observation. Temperature dependence of the average grain size(D) is categorized into three temperature regions, i.e. an incubation period for grain growth, rapid grain coarsening, and normal grain growth. The number of fine grains per unit area, however, is reduced remarkably even in incubation period. This leads to grain coarsening taking place continuously in the whole temperature regions. In contrast, the deformation texture scarcely changes even after full annealing at high temperatures. It is concluded that the annealing processes operating in hot-deformed magnesium alloy with continuous dynamic recrystallized grain structures can be mainly controlled by grain coarsening accompanied with no texture change, that is, continuous static recrystallization.展开更多
Grain size and texture changes of magnesium alloy AZ31 were studied in multidirectional forging(MDF) under decreasing temperature conditions.MDF was carried out up to large cumulative strains of 4.8 with changing the ...Grain size and texture changes of magnesium alloy AZ31 were studied in multidirectional forging(MDF) under decreasing temperature conditions.MDF was carried out up to large cumulative strains of 4.8 with changing the loading direction during decrease in temperature from pass to pass.MDF can accelerate the uniform development of fine-grained structures and increase the plastic workability at low temperatures.As a result,the MDFed alloy shows excellent higher strength as well as moderate ductility at room temperature even at the grain size below 1μm.Superplastic flow takes place at 423 K and depends on the anisotropy of MDFed samples.The mechanisms of strain-induced fine-grained structure development and of the plastic deformation were discussed in detail.展开更多
We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The ...We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The main idea is as follows. The distribution of the electric field around a thundercloud depends on the conductivity profile of the atmosphere. Quasi-static electric fields of a thundercloud decrease in those tropospheric regions where an increase of air conductivity is generated by pre-seismic activities due to emanation of radioactive gas and water into the lower atmosphere. The electric field becomes reduced in the lower troposphere, and the probability decreases of the cloud-to-ground (CG) strokes in such “contaminated” areas. Simultaneously, the electric field grows inside and above the thunderclouds, and hence, we anticipate a growth in the number of horizontal and tilted inter-cloud (or intra-cloud) (both termed as IC discharges) strokes. Spatial orientation of lightning strokes reduces vertical projection of their individual amplitudes, while the rate (median number strokes per a unit time) of discharges grows. We demonstrate that channel tilt of strokes modifies the spectral content of ELF/VLF radio noise and changes the rate of detected pulses during the earthquake preparation phase.展开更多
The effects of bacterial strain, salinity and pH on the bioleaching of a complex ore using mesophilic and extremely thermophilic bacteria were investigated and the statistical analysis of the results was performed usi...The effects of bacterial strain, salinity and pH on the bioleaching of a complex ore using mesophilic and extremely thermophilic bacteria were investigated and the statistical analysis of the results was performed using ERGUN’s test. The extreme thermophiles were shown to display superior kinetics of dissolution of zinc compared with the mesophiles as confirmed by the statistical analysis. Bioleaching performance of the extreme thermophiles is found to improve in response to the increase in acidity (pH from 2.0 to 1.0) whilst the activity of the mesophiles is adversely affected by decreasing pH. Statistical analysis of the bioleaching data indicates that the effect of pH is insignificant in the range of pH 1.0-1.2 for the extreme thermophiles and pH 1.4-2.0 for the mesophiles. Salinity is shown to have a suppressing effect on the mesophiles. However, the extreme thermophiles appear to be halophilic in character as they could operate efficiently under saline conditions (1%-4%Cl- (w/v)).展开更多
There has been enormous progress in the field of electromagnetic phenomena associated with earthquakes (EQs) and EQ prediction during the last three decades, and it is recently agreed that electromagnetic effects do a...There has been enormous progress in the field of electromagnetic phenomena associated with earthquakes (EQs) and EQ prediction during the last three decades, and it is recently agreed that electromagnetic effects do appear prior to an EQ. A few phenomena are well recognized as being statistically correlated with EQs as promising candidates for short-term EQ predictors: the first is ionospheric perturbation not only in the lower ionosphere as seen by subionospheric VLF (very low frequency, 3 kHz f 30 kHz)/LF (low frequency, 30 kHz f 300 kHz) propagation but also in the upper F region as detected by ionosondes, TEC (total electron content) observations, satellite observations, etc, and the second is DC earth current known as SES (Seismic electric signal). In addition to the above two physical phenomena, this review highlights the following four physical wave phenomena in ULF (ultra low frequency, frequency Hz)/ELF (extremely low frequency, 3 Hz frequency 3 kHz) ranges, including 1) ULF lithospheric radiation (i.e., direct radiation from the lithosphere), 2) ULF magnetic field depression effect (as an indicator of lower ionospheric perturbation), 3) ULF/ELF electromagnetic radiation (radiation in the atmosphere), and 4) Schumann resonance (SR) anomalies (as an indicator of the perturbations in the lower ionosphere and stratosphere). For each physical item, we will repeat the essential points and also discuss recent advances and future perspectives. For the purpose of future real EQ prediction practice, we pay attention to the statistical correlation of each phenomenon with EQs, and its predictability in terms of probability gain. Of course, all of those effects are recommended as plausible candidates for short-term EQ prediction, and they can be physically explained in terms of the unified concept of the lithosphere-atmosphere-ionosphere coupling (LAIC) process, so a brief description of this coupling has been carried out by using these four physical parameters though the mechanism of each phenomenon is still poorly展开更多
There have been published many papers on VLF (very low frequency) characteristics to study seismo-ionospheric perturbations. Usually VLF records (amplitude and/or phase) are used to investigate mainly the temporal evo...There have been published many papers on VLF (very low frequency) characteristics to study seismo-ionospheric perturbations. Usually VLF records (amplitude and/or phase) are used to investigate mainly the temporal evolution of VLF propagation anomalies with special attention to one particular propagation path. The most important advantage of this paper is the simultaneous use of several propagation paths. A succession of earthquakes (EQs) happened in the Kumamoto area in Kyusyu Island;two strong foreshocks with magnitude of 6.5 and 6.4 on 14 April (UT) and the main shock with magnitude 7.3 on 15 April (UT). Because the EQ epicenters are not far from the VLF transmitter (with the call sign of JJI in Miyazaki prefecture), we can utilize simultaneously 8 observing stations of our network all over Japan. Together with the use of theoretical computations based on wave-hop theory, we try to trace both the temporal and spatial evolutions of the ionospheric perturbation associated with this succession of EQs. It is found that the ionospheric perturbation begins to appear about two weeks before the EQs, and this perturbation becomes most developed 5 - 3 days before the main shock. When the perturbation is most disturbed, the maximum change in vertical direction is depletion in the VLF effective ionospheric height of the order of 10 km, and its horizontal scale (or its radius) is about 1000 km. These spatio-temporal changes of the seismo-ionospheric perturbation will be investigated in details in the discus-sion, a comparison has made with the VLF characteristics of the 1995 Kobe with the same magnitude and of the same fault-type, and a brief discussion on the generation mechanism of seismo-ionospheric perturbation is finally made.展开更多
The ultra-low frequency (ULF) magnetic field data at a station very close to the 2008 Sichuan earthquake (EQ) (on 12 May, 2008;M = 8.0) are extensively studied on the basis of combined statistical and natural time ana...The ultra-low frequency (ULF) magnetic field data at a station very close to the 2008 Sichuan earthquake (EQ) (on 12 May, 2008;M = 8.0) are extensively studied on the basis of combined statistical and natural time analyses. Two effects in ULF are treated: one is the well-known ULF radiation from the lithosphere, and the other is the non-conventional depression of ULF horizontal magnetic field. The simple statistical analysis has yielded: 1) no clear evidence of the presence of precursory ULF radiation, and 2) a significant effect of depression of ULF horizontal field a few days before the EQ (as a signature of ionospheric perturbations). The recently introduced natural time analysis has also been performed in order to study the critical features of the lithosphere and essentially new information has been brought about. The parameter “polarization”, as the ratio of vertical to horizontal components, showed critical features in the time period of 17 - 27 April, about one month to two weeks before the EQ as a signature of lithospheric radiation. Then, the natural time analysis has reconfirmed the presence of ionospheric perturbations a few days before the EQ, together with an additional time window found on 19 - 23 April, about one month before the EQ, exhibiting critical features in the ULF depression.展开更多
The hourly data of the vertical Z and the horizontal H components of 37 ground-based DC-ULF geomagnetic stations are examined during 20 April-12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, an...The hourly data of the vertical Z and the horizontal H components of 37 ground-based DC-ULF geomagnetic stations are examined during 20 April-12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, anomalies-a double low-point and a decreased amplitude-are registered on the curves of the Z component at 25 stations in a large-scale area surrounding the Wenchuan epicentral area. The H component shows none of the double low-point phenomenon but does exhibit a reduced magnitude at the same time. The geomagnetic index Kp is also examined and indicates that the anomalies appear at a solar quiet period. The appearing time shift(Tzs) between the first low-point on May 9 and the minimum point occurring time of May 1-5, 2008 is also checked.The results show that Tzs is on the order of 1-2 hours earlier or later than usual and there is a 2-6 hours’ gap between these two lowpoints. However, there is still a transition area which includes the epicenter where Tzs=0. Variation amplitude examined on vertical Z increases as the distance from the epicenter decreases. An Earth-air-ionosphere model has been employed to investigate a possible mechanism of this phenomenon and positive results have been unexpectedly attained. All these above-related results tend to prove that the variations of the Z and H on May 9, 2008 during the solar quiet period are probably associated with the forthcoming Wenchuan MS 8.0 earthquake.展开更多
Induction vectors have been extensively calculated using data from 19 Japanese observatories for a dozen years preceding the huge 2011 Tohoku earthquake (EQ). At 6 observatories anomalous variations of induction vecto...Induction vectors have been extensively calculated using data from 19 Japanese observatories for a dozen years preceding the huge 2011 Tohoku earthquake (EQ). At 6 observatories anomalous variations of induction vectors were separated in the years of 2008-2010 that can be identified as middle-term precursors. These observatories are located not at the shortest distance from the EQ epicenter, that is in agreement with the widely known phenomenon of spatial selectivity of EQ precursors. The analysis of horizontal tensors reveals a conductivity anomaly under the central part of the Boso peninsula (at 30 km from Tokyo) with a WNW-ESE strike coinciding both with the Sagami trough strike and the strike of well conducting 3 km thick sediments. A joint analysis of geoelectric and tectonic data leads to a preliminary conclusion that the Boso conductivity anomaly connects two large scale conductors: Pacific sea water and a deep magma reservoir beneath a volcanic belt. Between two so different conductors an unstable transition zone can be expected which should be sensitive to changes of stress. Applying our original processing including two steps analysis and elimination of annual and monthly periods, a short-term two-month-long precursor of bay-like form was successfully separated at the observatory of Kanozan, KNZ (over the Boso anomaly) despite its strong noise. All the results were obtained with advanced multi-windows multi-rr (remote reference) robust programs with a coherency control. Dependence of the results of induction vector calculation on geomagnetic activity was carefully studied, and this dependence is relatively strong when the magnetotelluric field and noise have approximately the same magnitude. But even in this case we could identify the precursor field.展开更多
There have been reported several papers on the ionospheric F region perturbations prior to the 2008 Sichuan earthquake (EQ) (magnitude 8.0), but it seems that very few reports have been published on the characteristic...There have been reported several papers on the ionospheric F region perturbations prior to the 2008 Sichuan earthquake (EQ) (magnitude 8.0), but it seems that very few reports have been published on the characteristics of ground-based ULF (ultra low frequency) magnetic field variations for this EQ. This paper deals with two different aspects of ground-based ULF magnetic field variations: 1) ULF radiation from the lithosphere, and 2) depression of ULF horizontal magnetic field as a signature of lower ionospheric perturbations. ULF data from two Chinese stations [Chengdu (epicentral distance, 80 km) and Xichang (about 300 km away from the EQ epicenter)] are analyzed, with paying attention to the local nighttime period (LT = 22 h to 02 h, UTC = 14 h to 18 h) in order to avoid man-made noise. We have analyzed powers of the horizontal component (H2), vertical component (Z2), polarization as their ratio (Z2/H2), depression of the horizontal component (as an inverse of horizontal magnetic field component power, 1/H2) and δDep as a variation of depression at a particular frequency of 0.01 - 0.02 Hz (10 - 20 mHz). It is then found that there seems no clear signature of lithospheric ULF radiation. Whilst, the most evident fact is the finding of depression of ULF horizontal magnetic field at Chengdu a few days before the Sichuan EQ, which suggests that the lower ionosphere was perturbed before the EQ. The characteristics of the lower ionospheric perturbations are compared with those of upper ionospheric perturbations reported before.展开更多
The relative importance of magnitude and depth of an earthquake (EQ) in the generation of seismo-ionospheric perturbations at middle latitudes is investigated by using the EQs near the propagation path from the Japane...The relative importance of magnitude and depth of an earthquake (EQ) in the generation of seismo-ionospheric perturbations at middle latitudes is investigated by using the EQs near the propagation path from the Japanese LF transmitter, JJY (at Fukushima) to a receiving station at Petropavsk-Kamchatsky (PTK) in Russia during a three-year period of 2005-2007. It is then found that the depth (down to 100km) is an extremely unimportant factor as compared with the magnitude in inducing seismo-ionospheric perturbations at middle latitudes. This result for sea EQs in the Izu-Bonin and Kurile-Kamchatka arcs is found to be in sharp contrast with our previous result for Japanese EQs mainly of the fault-type. We try to interpret this difference in the context of the lithosphere-atmosphere-ionosphere coupling mechanism.展开更多
After the 2011 Tohoku earthquake (EQ), there have been numerous aftershocks in the eastern and Pacific Ocean of Japan, but EQs are still rare in the western part of Japan. In this situation a relatively large (magnitu...After the 2011 Tohoku earthquake (EQ), there have been numerous aftershocks in the eastern and Pacific Ocean of Japan, but EQs are still rare in the western part of Japan. In this situation a relatively large (magnitude (M) ~6) EQ happened on April 12 (UT), 2013 at a place close to the former 1995 Kobe EQ (M~7), so we have tried to find whether there existed any precursors to this EQ, especially abnormal animal behavior (milk yield of cows), observed at Kagawa, Shikoku, near the EQ epicenter. The milk yield of cows has been continuously monitored at Kagawa, and it is found that the milk yield exhibited an abnormal depletion about 10 days before the EQ. This behavior has been extensively compared with the former electromagnetic precursors (ULF radiation, ionos-pheric perturbation). This leads to the discussion on the sensory mechanism of unusual behavior of mild yield of cows, and it may be suggested that ULF radiation among different electromagnetic precursors is a mostly likely driver, at least, for this EQ.展开更多
A statistical study on the basis of one-year data of 2014 has been performed in order to find whether abnormal animal behavior is related with seismic activity and also whether the ULF (Ultra Low Frequency) electromag...A statistical study on the basis of one-year data of 2014 has been performed in order to find whether abnormal animal behavior is related with seismic activity and also whether the ULF (Ultra Low Frequency) electromagnetic radiation might be a possible sensory mechanism of abnormal animal behavior. Abnormal animal behavior has been studied with the use of digitally recorded milk yield of cows at Ibaraki Prefecture Livestock Station, and the ULF magnetic field changes have been studied with the data at a magnetic observatory of Kakioka. As the result of correlation analyses, clear responses are observed for both the milk yield of cows and ULF magnetic field changes (both ULF radiation (ULF emissions from the lithosphere) and ULF depression (as an indicator of lower ionospheric perturbations)) for most powerful and not distant earthquakes (EQs) with magnitude > 6, that is, the milk yield of cows is found to exhibit a conspicuous depletion about 17 - 18 days before an EQ, though the correlation coefficient is not so big. Another important objective in this paper is to identify that ULF radiation is the main agent of abnormal behavior so that we have compared the temporal evolutions of milk yield of cows, ULF radiation and ULF depression for three major EQs. As a result, it is found that ULF radiation happens, at least, during the periods of abnormal depletion of milk yield of cows.展开更多
The Kumamoto area of Kyusyu Island was attacked by a series of large earthquakes (EQs) in April, 2016. The first two foreshocks had the magnitudes of 6.5 and 6.4, and about 1 day later there was the main shock on 15 A...The Kumamoto area of Kyusyu Island was attacked by a series of large earthquakes (EQs) in April, 2016. The first two foreshocks had the magnitudes of 6.5 and 6.4, and about 1 day later there was the main shock on 15 April (UT) with magnitude 7.3. These are fault-type EQs, and so we would expect a variety of electromagnetic precursors to these EQs because we had detected different phenomena for the 1995 Kobe EQ, same fault-type EQ. As for the lithospheric effect, the ULF data at Kanoya observatory (about 150 km from the EQ epicenters) are used, but the simple statistical analysis could not provide us with any clear evidence of ULF radiation from the lithosphere. However, our conventional analyses indicated clear signatures in the atmosphere as ULF/ELF impulsive emissions and also in the ionosphere as observed by means of VLF propagation anomalies and ULF depression. ULF/ELF radiation appeared on 8-11 April (in UT) (maximum on 10 and 11 April (UT)), while ULF depression took place on 8 and 10 April (in UT), so that both atmospheric radiation and ionospheric perturbation took place nearly during the same time period.展开更多
Study of seismo-ionospheric coupling mechanism demands the quiet geomagnetic condition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. In this manuscript, we present the eff...Study of seismo-ionospheric coupling mechanism demands the quiet geomagnetic condition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. In this manuscript, we present the effect of back to back two geomagnetic storms before a strong earthquake happened in Imphal, India on January 4, 2016 (M</span><span style="font-family:""> </span><span style="font-family:Verdana;">=</span><span style="font-family:""> </span><span style="font-family:Verdana;">6.7). We studied the lower ionospheric irregularities for </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> duration of 31 days by computing the nighttime fluctuations in Very Low Frequency (VLF) radio signal received transmitter JJI (22.2 kHz) in Japan at Ionospheric and Earthquake Research Centre & Optical Observatory (IERCOO), Sitapur, India. We also studied the presence of Atmospheric Gravity Wave (AGW) in nighttime VLF signal in lower ionospheric heights and the same computed that from SABER/TIMED satellite. Two geomagnetic storms occurred on December 21, and 31, 2015. By the conventional analysis, we found that there is a significant decrease in nighttime trend and an increase in nighttime fluctuations around 15 days before the earthquake and just on the first storm and thus the pre-seismic effects on VLF signal gets contaminated due to the presence of storms. The wave-like structure in VLF fluctuations shows significant increase in intensity by using Fourier and Wavelet analysis before the earthquake. By analysis of SABER data, we found significant enhancement in AGW around 10 days before the earthquake. As the wavelike structures are coming from neutral acoustics reasons from pressure or temperature variations, this paper exhibits a significant example of contamination in ionospheric parameters due to geomagnetic storm where the acoustics parameters remain un-contaminated.展开更多
Schumann resonance （SR） is an electromag- netic resonance phenomenon in the Earth-ionosphere cavity exited by global lightning activities when the wavelength matches the circumference of the Earth, and the lowest fo...Schumann resonance （SR） is an electromag- netic resonance phenomenon in the Earth-ionosphere cavity exited by global lightning activities when the wavelength matches the circumference of the Earth, and the lowest four peak frequencies of SR are about 8, 14, 20, and 26 Hz. This article presents the new observational data of SR in China. The observations of two horizontal mag- netic components （BNs and BEw） in the frequency band range of 3-29 Hz at Yongsheng observatory （26.7°N, 100.8°E） in southwestern China were mainly analyzed. It is found that the SR amplitudes at peak frequencies in BNs and BEw components all showed diurnal and seasonal variations, and that the SR amplitude in BNS component is always higher than that in BEw component. Diurnal vari- ation of SR amplitude around equinoxes and solstices inBNs component is related to active intervals of three global thunderstorm centers, while SR amplitude in BEw com- ponent is the most significant at around 16 LT, corre- sponding to Asian center. SR amplitudes both in BNs and BEw components increase in the rainy season from May to September. In addition, the SR anomalies in association with the 2011 Japan earthquake are exhibited. The anom- alous effect was characterized by an increase in amplitude at the lowest four SR modes beginning at 4 days before this earthquake. Upon analyzing the wave interference between the direct wave and disturbed wave scattered by localized modification of lower ionosphere over the epicenter, Asian and African thunderstorm centers are found to contribute to anomalous effect observed at Yongsheng station. Modeling results of SR regular and disturbed spectra at different local times led to the similar conclusion.展开更多
The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is ...The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is the acoustic cavitation due to the non-uniform distribution of acoustic pressure in the chamber.Cavitation has a strong impact on the surface degradation mechanisms.In this work,a numerical calculation of the acoustic pressure distribution inside the reactor chamber was performed using COMSOL Multiphysics.The numerical results have revealed the dependence of the structure of the acoustic pressure field on the boundary conditions for various thicknesses of the piezoelectric transducer.In particular,the amplitude of the acoustic pressure is minimal in the case of absorbing boundaries,and the attenuation becomes more significant as the thickness of the piezoelectric transducer increases.In addition,reflective boundaries play a significant role in the formation and distribution of zones of maximum cavitation activity.展开更多
This work is dedicated to the experimental study of the shear properties of three-dimensional reinforced composites taking into account their structural features,in Iosipescu tests.Shear strains have been determined u...This work is dedicated to the experimental study of the shear properties of three-dimensional reinforced composites taking into account their structural features,in Iosipescu tests.Shear strains have been determined using Vic-3D non-contact three-dimensional digital optical system.The evolution of inhomogeneous strain fields on the surface of composite specimens of the structure under study has been analyzed.The variants of strain averaging in the specimen working area have been analyzed using Vic-3D tools.AMSY-6 acoustic emission system has been used to assess the structural integrity of composite materials under loading.展开更多
The measurements of very low frequency/low frequency (VLF/LF) signals at the Petropavlovsk-Kamchatsky (PTK) and Yuzhno-Sakhalinsk (YSH) stations in Russia and several observing stations in Japan were used for the anal...The measurements of very low frequency/low frequency (VLF/LF) signals at the Petropavlovsk-Kamchatsky (PTK) and Yuzhno-Sakhalinsk (YSH) stations in Russia and several observing stations in Japan were used for the analysis of lower ionospheric perturbations in possible association with two earthquakes (EQs) which occurred offshore the Pacific Ocean of Japan in November 2016. The first EQ with M (magnitude) = 6.1 (depth 42 km) happened close to the coast line on 11 November (UT). The second EQ was recorded in the sea on 21 November (UT) with M = 6.9 (depth 11 km) and they had a series of aftershocks with M up to 5.6. As for the long-range monitoring, the significant negative nighttime amplitude decreases as propagation anomalies were found for two subionospheric paths: NWC (Australia)-PTK and JJY (Fukushima, Japan)-YSH during about a week, mainly before the first EQ. The anomalies of signal in the path JJY-PTK were observed 4 - 5 days before the second EQ and 3 days after it. Extensive analyses have been performed as well for these two EQs by using the short-range monitoring of VLF data observed at all of the seven VLF/LF stations in Japan in relation to the JJY signal. As related with the 1st EQ, there were observed anomalies on the two paths of JJY-STU (Suttsu) and JJY-NSB (Nakashibetsu) (both stations in Hokkaido) on 2 and 3 November. While, for the 2nd EQ clear anomalies have been observed on 14 and 15, and on 21 November at Ito station in Izu peninsula, Kamakura, Togane and Katsuura in Chiba. Taking into account the possible influence of other factors which can produce perturbations in VLF/LF signals and also using control paths, we may conclude that observed anomalies were very likely to be signatures of lower ionospheric perturbations caused by impending EQs. Finally, we try to estimate the possible perturbation scale for both EQs.展开更多
文摘The dynamic recrystallization(DRX) and texture development, taking place during hot deformation of magnesium alloy AZ31 with a strong wire texture, were studied in compression at 673 K (0.73 Tm). Two kinds of samples were machined parallelly to the extruded and transverse directions of Mg alloy rods. New fine grains are evolved at original grain boundaries corrugated at low strains and develop rapidly in the medium range of strain, finally leading to a roughly full evolution of equiaxial fine grains. Kink bands are evolved at grain boundaries corrugated and also frequently in grain interiors at low strains. The boundary misorientations of kink band increase rapidly with increasing strain and approach a saturation value in high strain. The average size of the regions fragmented by kink band is almost the same as that of new grains evolved in high strain. These characteristics of new grain evolution process are not changed by the orientation of the samples, while the flow behaviors clearly depend on it. It is concluded that new grain evolution can be controlled by a deformation-induced continuous reaction, i.e. continuous dynamic recrystallization(DRX). The latter is discussed by comparing with conventional, i.e. discontinuous DRX.
基金Project(AF-2005006) supported by the Amada Foundation for Metal Work Technology and the Light Metals Educational Foundation, Japan
文摘Annealing behaviors of hot-deformed magnesium alloy AZ31 were studied at temperatures from 300 to 673 K by optical and SEM/EBSD metallographic observation. Temperature dependence of the average grain size(D) is categorized into three temperature regions, i.e. an incubation period for grain growth, rapid grain coarsening, and normal grain growth. The number of fine grains per unit area, however, is reduced remarkably even in incubation period. This leads to grain coarsening taking place continuously in the whole temperature regions. In contrast, the deformation texture scarcely changes even after full annealing at high temperatures. It is concluded that the annealing processes operating in hot-deformed magnesium alloy with continuous dynamic recrystallized grain structures can be mainly controlled by grain coarsening accompanied with no texture change, that is, continuous static recrystallization.
文摘Grain size and texture changes of magnesium alloy AZ31 were studied in multidirectional forging(MDF) under decreasing temperature conditions.MDF was carried out up to large cumulative strains of 4.8 with changing the loading direction during decrease in temperature from pass to pass.MDF can accelerate the uniform development of fine-grained structures and increase the plastic workability at low temperatures.As a result,the MDFed alloy shows excellent higher strength as well as moderate ductility at room temperature even at the grain size below 1μm.Superplastic flow takes place at 423 K and depends on the anisotropy of MDFed samples.The mechanisms of strain-induced fine-grained structure development and of the plastic deformation were discussed in detail.
文摘We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The main idea is as follows. The distribution of the electric field around a thundercloud depends on the conductivity profile of the atmosphere. Quasi-static electric fields of a thundercloud decrease in those tropospheric regions where an increase of air conductivity is generated by pre-seismic activities due to emanation of radioactive gas and water into the lower atmosphere. The electric field becomes reduced in the lower troposphere, and the probability decreases of the cloud-to-ground (CG) strokes in such “contaminated” areas. Simultaneously, the electric field grows inside and above the thunderclouds, and hence, we anticipate a growth in the number of horizontal and tilted inter-cloud (or intra-cloud) (both termed as IC discharges) strokes. Spatial orientation of lightning strokes reduces vertical projection of their individual amplitudes, while the rate (median number strokes per a unit time) of discharges grows. We demonstrate that channel tilt of strokes modifies the spectral content of ELF/VLF radio noise and changes the rate of detected pulses during the earthquake preparation phase.
文摘The effects of bacterial strain, salinity and pH on the bioleaching of a complex ore using mesophilic and extremely thermophilic bacteria were investigated and the statistical analysis of the results was performed using ERGUN’s test. The extreme thermophiles were shown to display superior kinetics of dissolution of zinc compared with the mesophiles as confirmed by the statistical analysis. Bioleaching performance of the extreme thermophiles is found to improve in response to the increase in acidity (pH from 2.0 to 1.0) whilst the activity of the mesophiles is adversely affected by decreasing pH. Statistical analysis of the bioleaching data indicates that the effect of pH is insignificant in the range of pH 1.0-1.2 for the extreme thermophiles and pH 1.4-2.0 for the mesophiles. Salinity is shown to have a suppressing effect on the mesophiles. However, the extreme thermophiles appear to be halophilic in character as they could operate efficiently under saline conditions (1%-4%Cl- (w/v)).
文摘There has been enormous progress in the field of electromagnetic phenomena associated with earthquakes (EQs) and EQ prediction during the last three decades, and it is recently agreed that electromagnetic effects do appear prior to an EQ. A few phenomena are well recognized as being statistically correlated with EQs as promising candidates for short-term EQ predictors: the first is ionospheric perturbation not only in the lower ionosphere as seen by subionospheric VLF (very low frequency, 3 kHz f 30 kHz)/LF (low frequency, 30 kHz f 300 kHz) propagation but also in the upper F region as detected by ionosondes, TEC (total electron content) observations, satellite observations, etc, and the second is DC earth current known as SES (Seismic electric signal). In addition to the above two physical phenomena, this review highlights the following four physical wave phenomena in ULF (ultra low frequency, frequency Hz)/ELF (extremely low frequency, 3 Hz frequency 3 kHz) ranges, including 1) ULF lithospheric radiation (i.e., direct radiation from the lithosphere), 2) ULF magnetic field depression effect (as an indicator of lower ionospheric perturbation), 3) ULF/ELF electromagnetic radiation (radiation in the atmosphere), and 4) Schumann resonance (SR) anomalies (as an indicator of the perturbations in the lower ionosphere and stratosphere). For each physical item, we will repeat the essential points and also discuss recent advances and future perspectives. For the purpose of future real EQ prediction practice, we pay attention to the statistical correlation of each phenomenon with EQs, and its predictability in terms of probability gain. Of course, all of those effects are recommended as plausible candidates for short-term EQ prediction, and they can be physically explained in terms of the unified concept of the lithosphere-atmosphere-ionosphere coupling (LAIC) process, so a brief description of this coupling has been carried out by using these four physical parameters though the mechanism of each phenomenon is still poorly
文摘There have been published many papers on VLF (very low frequency) characteristics to study seismo-ionospheric perturbations. Usually VLF records (amplitude and/or phase) are used to investigate mainly the temporal evolution of VLF propagation anomalies with special attention to one particular propagation path. The most important advantage of this paper is the simultaneous use of several propagation paths. A succession of earthquakes (EQs) happened in the Kumamoto area in Kyusyu Island;two strong foreshocks with magnitude of 6.5 and 6.4 on 14 April (UT) and the main shock with magnitude 7.3 on 15 April (UT). Because the EQ epicenters are not far from the VLF transmitter (with the call sign of JJI in Miyazaki prefecture), we can utilize simultaneously 8 observing stations of our network all over Japan. Together with the use of theoretical computations based on wave-hop theory, we try to trace both the temporal and spatial evolutions of the ionospheric perturbation associated with this succession of EQs. It is found that the ionospheric perturbation begins to appear about two weeks before the EQs, and this perturbation becomes most developed 5 - 3 days before the main shock. When the perturbation is most disturbed, the maximum change in vertical direction is depletion in the VLF effective ionospheric height of the order of 10 km, and its horizontal scale (or its radius) is about 1000 km. These spatio-temporal changes of the seismo-ionospheric perturbation will be investigated in details in the discus-sion, a comparison has made with the VLF characteristics of the 1995 Kobe with the same magnitude and of the same fault-type, and a brief discussion on the generation mechanism of seismo-ionospheric perturbation is finally made.
文摘The ultra-low frequency (ULF) magnetic field data at a station very close to the 2008 Sichuan earthquake (EQ) (on 12 May, 2008;M = 8.0) are extensively studied on the basis of combined statistical and natural time analyses. Two effects in ULF are treated: one is the well-known ULF radiation from the lithosphere, and the other is the non-conventional depression of ULF horizontal magnetic field. The simple statistical analysis has yielded: 1) no clear evidence of the presence of precursory ULF radiation, and 2) a significant effect of depression of ULF horizontal field a few days before the EQ (as a signature of ionospheric perturbations). The recently introduced natural time analysis has also been performed in order to study the critical features of the lithosphere and essentially new information has been brought about. The parameter “polarization”, as the ratio of vertical to horizontal components, showed critical features in the time period of 17 - 27 April, about one month to two weeks before the EQ as a signature of lithospheric radiation. Then, the natural time analysis has reconfirmed the presence of ionospheric perturbations a few days before the EQ, together with an additional time window found on 19 - 23 April, about one month before the EQ, exhibiting critical features in the ULF depression.
基金supported by NSFC (National Natural Science Foundation of China) under grant agreement No.41774084National Key R & D Program of China under grant No.2018YFC 1503506
文摘The hourly data of the vertical Z and the horizontal H components of 37 ground-based DC-ULF geomagnetic stations are examined during 20 April-12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, anomalies-a double low-point and a decreased amplitude-are registered on the curves of the Z component at 25 stations in a large-scale area surrounding the Wenchuan epicentral area. The H component shows none of the double low-point phenomenon but does exhibit a reduced magnitude at the same time. The geomagnetic index Kp is also examined and indicates that the anomalies appear at a solar quiet period. The appearing time shift(Tzs) between the first low-point on May 9 and the minimum point occurring time of May 1-5, 2008 is also checked.The results show that Tzs is on the order of 1-2 hours earlier or later than usual and there is a 2-6 hours’ gap between these two lowpoints. However, there is still a transition area which includes the epicenter where Tzs=0. Variation amplitude examined on vertical Z increases as the distance from the epicenter decreases. An Earth-air-ionosphere model has been employed to investigate a possible mechanism of this phenomenon and positive results have been unexpectedly attained. All these above-related results tend to prove that the variations of the Z and H on May 9, 2008 during the solar quiet period are probably associated with the forthcoming Wenchuan MS 8.0 earthquake.
文摘Induction vectors have been extensively calculated using data from 19 Japanese observatories for a dozen years preceding the huge 2011 Tohoku earthquake (EQ). At 6 observatories anomalous variations of induction vectors were separated in the years of 2008-2010 that can be identified as middle-term precursors. These observatories are located not at the shortest distance from the EQ epicenter, that is in agreement with the widely known phenomenon of spatial selectivity of EQ precursors. The analysis of horizontal tensors reveals a conductivity anomaly under the central part of the Boso peninsula (at 30 km from Tokyo) with a WNW-ESE strike coinciding both with the Sagami trough strike and the strike of well conducting 3 km thick sediments. A joint analysis of geoelectric and tectonic data leads to a preliminary conclusion that the Boso conductivity anomaly connects two large scale conductors: Pacific sea water and a deep magma reservoir beneath a volcanic belt. Between two so different conductors an unstable transition zone can be expected which should be sensitive to changes of stress. Applying our original processing including two steps analysis and elimination of annual and monthly periods, a short-term two-month-long precursor of bay-like form was successfully separated at the observatory of Kanozan, KNZ (over the Boso anomaly) despite its strong noise. All the results were obtained with advanced multi-windows multi-rr (remote reference) robust programs with a coherency control. Dependence of the results of induction vector calculation on geomagnetic activity was carefully studied, and this dependence is relatively strong when the magnetotelluric field and noise have approximately the same magnitude. But even in this case we could identify the precursor field.
文摘There have been reported several papers on the ionospheric F region perturbations prior to the 2008 Sichuan earthquake (EQ) (magnitude 8.0), but it seems that very few reports have been published on the characteristics of ground-based ULF (ultra low frequency) magnetic field variations for this EQ. This paper deals with two different aspects of ground-based ULF magnetic field variations: 1) ULF radiation from the lithosphere, and 2) depression of ULF horizontal magnetic field as a signature of lower ionospheric perturbations. ULF data from two Chinese stations [Chengdu (epicentral distance, 80 km) and Xichang (about 300 km away from the EQ epicenter)] are analyzed, with paying attention to the local nighttime period (LT = 22 h to 02 h, UTC = 14 h to 18 h) in order to avoid man-made noise. We have analyzed powers of the horizontal component (H2), vertical component (Z2), polarization as their ratio (Z2/H2), depression of the horizontal component (as an inverse of horizontal magnetic field component power, 1/H2) and δDep as a variation of depression at a particular frequency of 0.01 - 0.02 Hz (10 - 20 mHz). It is then found that there seems no clear signature of lithospheric ULF radiation. Whilst, the most evident fact is the finding of depression of ULF horizontal magnetic field at Chengdu a few days before the Sichuan EQ, which suggests that the lower ionosphere was perturbed before the EQ. The characteristics of the lower ionospheric perturbations are compared with those of upper ionospheric perturbations reported before.
文摘The relative importance of magnitude and depth of an earthquake (EQ) in the generation of seismo-ionospheric perturbations at middle latitudes is investigated by using the EQs near the propagation path from the Japanese LF transmitter, JJY (at Fukushima) to a receiving station at Petropavsk-Kamchatsky (PTK) in Russia during a three-year period of 2005-2007. It is then found that the depth (down to 100km) is an extremely unimportant factor as compared with the magnitude in inducing seismo-ionospheric perturbations at middle latitudes. This result for sea EQs in the Izu-Bonin and Kurile-Kamchatka arcs is found to be in sharp contrast with our previous result for Japanese EQs mainly of the fault-type. We try to interpret this difference in the context of the lithosphere-atmosphere-ionosphere coupling mechanism.
文摘After the 2011 Tohoku earthquake (EQ), there have been numerous aftershocks in the eastern and Pacific Ocean of Japan, but EQs are still rare in the western part of Japan. In this situation a relatively large (magnitude (M) ~6) EQ happened on April 12 (UT), 2013 at a place close to the former 1995 Kobe EQ (M~7), so we have tried to find whether there existed any precursors to this EQ, especially abnormal animal behavior (milk yield of cows), observed at Kagawa, Shikoku, near the EQ epicenter. The milk yield of cows has been continuously monitored at Kagawa, and it is found that the milk yield exhibited an abnormal depletion about 10 days before the EQ. This behavior has been extensively compared with the former electromagnetic precursors (ULF radiation, ionos-pheric perturbation). This leads to the discussion on the sensory mechanism of unusual behavior of mild yield of cows, and it may be suggested that ULF radiation among different electromagnetic precursors is a mostly likely driver, at least, for this EQ.
文摘A statistical study on the basis of one-year data of 2014 has been performed in order to find whether abnormal animal behavior is related with seismic activity and also whether the ULF (Ultra Low Frequency) electromagnetic radiation might be a possible sensory mechanism of abnormal animal behavior. Abnormal animal behavior has been studied with the use of digitally recorded milk yield of cows at Ibaraki Prefecture Livestock Station, and the ULF magnetic field changes have been studied with the data at a magnetic observatory of Kakioka. As the result of correlation analyses, clear responses are observed for both the milk yield of cows and ULF magnetic field changes (both ULF radiation (ULF emissions from the lithosphere) and ULF depression (as an indicator of lower ionospheric perturbations)) for most powerful and not distant earthquakes (EQs) with magnitude > 6, that is, the milk yield of cows is found to exhibit a conspicuous depletion about 17 - 18 days before an EQ, though the correlation coefficient is not so big. Another important objective in this paper is to identify that ULF radiation is the main agent of abnormal behavior so that we have compared the temporal evolutions of milk yield of cows, ULF radiation and ULF depression for three major EQs. As a result, it is found that ULF radiation happens, at least, during the periods of abnormal depletion of milk yield of cows.
文摘The Kumamoto area of Kyusyu Island was attacked by a series of large earthquakes (EQs) in April, 2016. The first two foreshocks had the magnitudes of 6.5 and 6.4, and about 1 day later there was the main shock on 15 April (UT) with magnitude 7.3. These are fault-type EQs, and so we would expect a variety of electromagnetic precursors to these EQs because we had detected different phenomena for the 1995 Kobe EQ, same fault-type EQ. As for the lithospheric effect, the ULF data at Kanoya observatory (about 150 km from the EQ epicenters) are used, but the simple statistical analysis could not provide us with any clear evidence of ULF radiation from the lithosphere. However, our conventional analyses indicated clear signatures in the atmosphere as ULF/ELF impulsive emissions and also in the ionosphere as observed by means of VLF propagation anomalies and ULF depression. ULF/ELF radiation appeared on 8-11 April (in UT) (maximum on 10 and 11 April (UT)), while ULF depression took place on 8 and 10 April (in UT), so that both atmospheric radiation and ionospheric perturbation took place nearly during the same time period.
文摘Study of seismo-ionospheric coupling mechanism demands the quiet geomagnetic condition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. In this manuscript, we present the effect of back to back two geomagnetic storms before a strong earthquake happened in Imphal, India on January 4, 2016 (M</span><span style="font-family:""> </span><span style="font-family:Verdana;">=</span><span style="font-family:""> </span><span style="font-family:Verdana;">6.7). We studied the lower ionospheric irregularities for </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> duration of 31 days by computing the nighttime fluctuations in Very Low Frequency (VLF) radio signal received transmitter JJI (22.2 kHz) in Japan at Ionospheric and Earthquake Research Centre & Optical Observatory (IERCOO), Sitapur, India. We also studied the presence of Atmospheric Gravity Wave (AGW) in nighttime VLF signal in lower ionospheric heights and the same computed that from SABER/TIMED satellite. Two geomagnetic storms occurred on December 21, and 31, 2015. By the conventional analysis, we found that there is a significant decrease in nighttime trend and an increase in nighttime fluctuations around 15 days before the earthquake and just on the first storm and thus the pre-seismic effects on VLF signal gets contaminated due to the presence of storms. The wave-like structure in VLF fluctuations shows significant increase in intensity by using Fourier and Wavelet analysis before the earthquake. By analysis of SABER data, we found significant enhancement in AGW around 10 days before the earthquake. As the wavelike structures are coming from neutral acoustics reasons from pressure or temperature variations, this paper exhibits a significant example of contamination in ionospheric parameters due to geomagnetic storm where the acoustics parameters remain un-contaminated.
基金supported by the Basic Research Project of Institute of Earthquake Science,CEA (2013IES0101,2010IES0202)
文摘Schumann resonance （SR） is an electromag- netic resonance phenomenon in the Earth-ionosphere cavity exited by global lightning activities when the wavelength matches the circumference of the Earth, and the lowest four peak frequencies of SR are about 8, 14, 20, and 26 Hz. This article presents the new observational data of SR in China. The observations of two horizontal mag- netic components （BNs and BEw） in the frequency band range of 3-29 Hz at Yongsheng observatory （26.7°N, 100.8°E） in southwestern China were mainly analyzed. It is found that the SR amplitudes at peak frequencies in BNs and BEw components all showed diurnal and seasonal variations, and that the SR amplitude in BNS component is always higher than that in BEw component. Diurnal vari- ation of SR amplitude around equinoxes and solstices inBNs component is related to active intervals of three global thunderstorm centers, while SR amplitude in BEw com- ponent is the most significant at around 16 LT, corre- sponding to Asian center. SR amplitudes both in BNs and BEw components increase in the rainy season from May to September. In addition, the SR anomalies in association with the 2011 Japan earthquake are exhibited. The anom- alous effect was characterized by an increase in amplitude at the lowest four SR modes beginning at 4 days before this earthquake. Upon analyzing the wave interference between the direct wave and disturbed wave scattered by localized modification of lower ionosphere over the epicenter, Asian and African thunderstorm centers are found to contribute to anomalous effect observed at Yongsheng station. Modeling results of SR regular and disturbed spectra at different local times led to the similar conclusion.
文摘The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is the acoustic cavitation due to the non-uniform distribution of acoustic pressure in the chamber.Cavitation has a strong impact on the surface degradation mechanisms.In this work,a numerical calculation of the acoustic pressure distribution inside the reactor chamber was performed using COMSOL Multiphysics.The numerical results have revealed the dependence of the structure of the acoustic pressure field on the boundary conditions for various thicknesses of the piezoelectric transducer.In particular,the amplitude of the acoustic pressure is minimal in the case of absorbing boundaries,and the attenuation becomes more significant as the thickness of the piezoelectric transducer increases.In addition,reflective boundaries play a significant role in the formation and distribution of zones of maximum cavitation activity.
基金the Russian Foundation for Basic Research within the Projects(Grants 19-31-90148 and 18-01-00763)The experimental studies of shear material properties were conducted within the State Assignment of the Ministry of Education and Science of the Russian Federation(9.7529.2017/9.10).
文摘This work is dedicated to the experimental study of the shear properties of three-dimensional reinforced composites taking into account their structural features,in Iosipescu tests.Shear strains have been determined using Vic-3D non-contact three-dimensional digital optical system.The evolution of inhomogeneous strain fields on the surface of composite specimens of the structure under study has been analyzed.The variants of strain averaging in the specimen working area have been analyzed using Vic-3D tools.AMSY-6 acoustic emission system has been used to assess the structural integrity of composite materials under loading.
文摘The measurements of very low frequency/low frequency (VLF/LF) signals at the Petropavlovsk-Kamchatsky (PTK) and Yuzhno-Sakhalinsk (YSH) stations in Russia and several observing stations in Japan were used for the analysis of lower ionospheric perturbations in possible association with two earthquakes (EQs) which occurred offshore the Pacific Ocean of Japan in November 2016. The first EQ with M (magnitude) = 6.1 (depth 42 km) happened close to the coast line on 11 November (UT). The second EQ was recorded in the sea on 21 November (UT) with M = 6.9 (depth 11 km) and they had a series of aftershocks with M up to 5.6. As for the long-range monitoring, the significant negative nighttime amplitude decreases as propagation anomalies were found for two subionospheric paths: NWC (Australia)-PTK and JJY (Fukushima, Japan)-YSH during about a week, mainly before the first EQ. The anomalies of signal in the path JJY-PTK were observed 4 - 5 days before the second EQ and 3 days after it. Extensive analyses have been performed as well for these two EQs by using the short-range monitoring of VLF data observed at all of the seven VLF/LF stations in Japan in relation to the JJY signal. As related with the 1st EQ, there were observed anomalies on the two paths of JJY-STU (Suttsu) and JJY-NSB (Nakashibetsu) (both stations in Hokkaido) on 2 and 3 November. While, for the 2nd EQ clear anomalies have been observed on 14 and 15, and on 21 November at Ito station in Izu peninsula, Kamakura, Togane and Katsuura in Chiba. Taking into account the possible influence of other factors which can produce perturbations in VLF/LF signals and also using control paths, we may conclude that observed anomalies were very likely to be signatures of lower ionospheric perturbations caused by impending EQs. Finally, we try to estimate the possible perturbation scale for both EQs.
