Search

For the accuracy of simulated water surface profiles, the choosing of the required Manning coefficient is important. Furthermore, in the analysis of flow in open-channel, especially in hydraulic modeling, channel roughness variable forecasting is done. Therefore, it is important to calibrate the channel coefficient roughness for open channels, either artificial or natural. In the current investigation, the magnitude of Manning's coefficient “n” is occurred to calibrate the magnitude of the “n” coefficient by contrasting the simulated profiles of water surface with one reported, utilizing the HEC-RAS turbulent flow model for the Euphrates canal. The flows for the year 2020 were considered for this calibration. The magnitude of the roughness coefficient of Manning for the Euphrates river from Hindiya dam to Kufa dam indicates a strong agreement between the water surface profiles of observed and computed, n = 0.045 and n = 0.047 for the major channel and floodplain, respectively.

An approach to modelling volatile financial return series using stationary d-vine copula processes combined with Lebesgue-measure-preserving transformations known as v-transforms is proposed. By developing a method of stochastically inverting v-transforms, models are constructed that can describe both stochastic volatility in the magnitude of price movements and serial correlation in their directions. In combination with parametric marginal distributions it is shown that these models can rival and sometimes outperform well-known models in the extended GARCH family. 1

Monthly rainfall data for Blue Nile Basin (BNB) were obtained from the Ethiopian Meteorological Authority (1950–2018). Long-term trends in the BNB annual and monthly rainfall are investigated in this study. The challenges of the paper were to explore the impact of climate change on the study area using sound practical methods. The paper used the widely used statistical methods to find precisely the significance of the impact of climate change rainfall variability and distribution both spatially and temporally in the BNB. The statistical significance of the trend in the study is calculated by the Mann-Kendall (MK) test. Data were analyzed using the coefficient of variation, anomaly index, and precipitation concentration index. The coefficient of variation is high in Kiremt rainfall which implies more inter-annual variability of Bega rainfall than Kiremt (Coefficient of Variation (CV): Bega˃ Belg˃ Kiremt season). Based on Precipitation Concentration Index (PCI) value, the number of moderate concentration years (89.9%) has been increasing through time and the study area has encountered successive years of drought. The results showed that the annual, Bega, Belg, and Kiremt precipitation over the whole of BNB is significantly decreasing except Bega season with a magnitude of 36.38, 3.8, 7.8, and 24.7 mm per decade respectively. The rainfall in the study area is characterized by a high CV. Moreover, prolonged droughts have become common which adversely affects the agricultural system. It was also found that very low values of rainfall anomalies that correspond to severe droughts were associated with El Nino Southern Oscillation (ENSO) events.

The mechanical failure of fault plane during fluid injection can be conveniently approached by numerical methods, and the results can be applied in fault slip analysis to determine the corresponding magnitude of induced seismicity. During hydrofracturing, when faults are present and the fluid is injected into the fault, micro-seismic events are possible, although the magnitude is often somewhat larger than those associated with micro-seismic events produced from regular hydraulic fracturing because of the larger surface area available for fault rupture. This study considers the rate at which the changing elastic properties of materials influences the magnitude of seismic event during fault injection. The simulation is carried out under varying injection flow rates from 0.18 kg/s to 0.3 kg/s, and the thermo-hydro-mechanical (THM) model in FLAC3D is adopted. As the material elastic moduli increase significantly under isothermal injection, the resulted non-uniformity in the fault slip timing affects the magnitude of injection-induced seismicity. Rocks with lower moduli produced higher slip distance and seismicity during shear failure. However, in the coupled thermal case, the magnitudes of seismicity during injection are largely enhanced at lower elastic properties, which suggests that the energy of accumulated fluid pressure produces a larger rupture and longer slip displacement in cold injection than in the isothermal case. The resulting volumetric strain, both in the fault zone and in the matrix, is higher in lower moduli, meanwhile, it is much developed in non-isothermal injection as a result of the rock's response to the sum effect of thermal strain and the stress-induced strain.

We analyzed the number of cumulative positive cases of COVID-19 as a function of time in countries around the World. We tracked the increase in cases from the onset of the pandemic in each region for up to 150 days. We found that in 81 out of 146 regions the trajectory was described with a power-law function for up to 30 days. We also detected scale-free properties in the majority of sub-regions in Australia, Canada, China, and the United States (US). We developed an allometric model that was capable of fitting the initial phase of the pandemic and was the best predictor for the propagation of the illness for up to 100 days. We then determined that the power-law COVID-19 exponent correlated with measurements of human mobility. The COVID-19 exponent correlated with the magnitude of air passengers per country. This correlation persisted when we analyzed the number of air passengers per US states, and even per US metropolitan areas. Furthermore, the COVID-19 exponent correlated with the number of vehicle miles travelled in the US. Together, air and vehicular travel explained 70 % of the variability of the COVID-19 exponent. Taken together, our results suggest that the scale-free propagation of the virus is present at multiple geographical scales and is correlated with human mobility. We conclude that models of disease transmission should integrate scale-free dynamics as part of the modeling strategy and not only as an emergent phenomenological property.

Solar eclipses provide an excellent opportunity to study the effects of a sudden localized change in photoionization flux in the Earth's ionosphere and its consequent repercussion in the Geomagnetic field. We have focused on a subset of the data available from the North American 2017 eclipse in order to study VTEC measurements from GNSS data and geomagnetic field estimations from INTERMAGNET observatories near the eclipse path. Our simultaneous analysis of both datasets allowed us to quantify the ionosphere and magnetic field reaction to the eclipse event with which allowed us to compare how differently these take place in time. We found that studying the behaviour of VTEC differences with respect to reference values provides better insight of the actual eclipse effect and were able to characterize the dependence of parameters such as time delay of maximum depletion and recovery phase. We were also able to test models that link the ionospheric variations in a quantitative manner. Total electron content depletion measured from GNSS were fed into an approximation of Ashour-Chapman model at the locations of geomagnetic observatories and its predictions match the behaviour of magnetic field components in time and magnitude strikingly accurately., Comment: Accepted for publication in Advances in Space Research

Accurate representation of ionospheric equivalent slab thickness (τ) and scale height (Hm) plays a crucial role in characterizing the complex dynamics of topside and bottomside ionospheric constituents. In the present work, we examined the corresponding morphologies of ionospheric profile parameters with collocated global positioning system (GPS) and Digisonde Portable Sounder (DPS) setups at an equatorial location in west Africa Ilorin (8.50°N, 4.68°E), during a low solar activity year 2010. The extracted τ from GPS and DPS in selected quiet periods confirm it to be a first-order measure of Hm over Africa. The seasonal analysis of τ shows substantial enhancement in the magnitude during the post-sunset and solstice seasons, of which December solstice manifests relatively higher values than June solstice. This result could be associated with the elevation of the meridional wind and drift in the parameters, which are more substantial during the post-noon and solstices. Therefore, at solstices, the post-night increase could indicate solar cycle dynamics during HSA (high solar activity) and LSA (low solar activity). However, the extracted Hm from its relationship with τ did not show visible effects of dynamics in E × B plasma drift and the meridional wind. In our study, a decline in morphologies of Hm and τ from December solstice to June solstice through the equinox is not consistent with the existing observations at mid-latitude. The results would complement the relationships between bottomside and topside profile peak parameters and dynamics of ionospheric constituents for a realistic representation and modeling of the ionosphere over African equatorial and low latitude regions. Thus, it also contributes to the global effort of improving ionospheric prediction and forecasting models.

It is widely accepted that a quiet time equatorial electrojet (EEJ) varies daily, monthly, seasonally, and longitudinally; however, detailed characterization of these variations has not yet been done using multiple ground based stations. Therefore, the purpose of this article is to give a reasonably comprehensive comparison of day-to-day, monthly, seasonal, and longitudinal variabilities of the EEJ and its reversal counter electrojet (CEJ) occurrence during the period from 2011 to 2013. The analysis is based on a 1-minute ground-based magnetic data recorded at eight dip equatorial stations. The results obtained in this study indicate that the mean day-side EEJ is strongest around equinoxes months in the Peruvian, Southeast Asia and Philippine regions throughout the years investigated. On the other hand, stations in the African and Indian regions show medium peaks in the equinoxes months of the years 2011 - 2012. The EEJ strength in the Pacific sector is weakest throughout the years. The observed seasonal behavior of the peak EEJ during equinox is observed at 10:30 - 12:00 LT for Peruvian, Southeast Asian, and Philippine regions, but in the West African and Indian sectors, the medium EEJ peaks were observed about 1 hour earlier. We also found that, on average, morning CEJ events occur more frequently than in the evening CEJ at TTB followed by AAE and HUA. The largest morning CEJ fluctuations were observed for the TTB during the whole months of the years considered in this study except the December months of 2012. During the December solstice months of 2011, the EEJ current in TTB is maximum while the medium peak has been shown in 2012 and 2013. Overall the observed average EEJ strength is maximum during equinoxes and minimum in solstices months as well as seasons. Our results also show that the magnitude of EEJ gradually increases in the Peruvian and Southeast Asian sectors while the rate of MCEJ occurrence increases at Brazilian and African regions from the years 2011 to 2013. It is also observed that the magnitude of EEJ is highering during the years of the increasing solar cycle.

Continental earthquakes, especially shallow earthquakes, can cause disasters in populated areas. On 20 May 2016, a moderate magnitude earthquake (Mw 6.0) ruptured on Northern Territory of Australia. With the aim of seismic hazard assessment, coseismic and postsesmic deformation of the Petermann earthquake has been determined using ALOS-2 ascending and Sentinel-1A descending images. The coseismic deformation field suggests that the earthquake ruptured in the NNW direction with a length of about 20 km, a rake angle of 57.1° and a moment magnitude of Mw 6.06. The maximum slip of 1.31 m can be observed at the depth of 1.25 km. The small baseline subset (SBAS) InSAR was utilized to obtain the postseismic deformation from 69 Sentinel-1A images in a descending orbit. The spatiotemporal evolution of the postseismic deformation presents a gradually decaying trend, with a maximum displacement of 5.4 cm within 858 days after the mainshock. Our afterslip model suggests that the maximum slip of 0.28 m occurred at the depth of 0.25 km with a slight shift to the northwest compared to the coseismic slip. The static Coulomb failure stress (CFS) changes at various depths were calculated, indicating the consistency between high loaded stress zones and aftershock distribution.

Monitoring ionospheric scintillation on a global scale requires introducing a network of widely distributed geodetic receivers, which call for a special type of scintillation index due to the low sampling rate of such receivers. ROTI, as a scintillation index with great potential being applied in geodetic receivers globally, lacks extensive verification in the high-latitude region. Taking the phase scintillation index ( σ ϕ ) provided by ionospheric scintillation monitoring receivers as the reference, this paper analyses data collected at 8 high-latitude GNSS stations to validate the performance of ROTI statistically. The data is evaluated against 4 parameters: 1, the detected daily scintillation occurrence rate; 2, the ability to detect the daily occurrence pattern of ionospheric scintillation; 3, the correlation between the detected scintillation and the space weather parameters, including the 10.7 cm solar flux, Ap, the H component of longitudinally asymmetric and polar cap north indices; 4, the overall distribution of the scintillation magnitude. Results reveal that the scintillation occurrence rates, the occurrence patterns of ionospheric scintillations and the correlations provided by ROTI are generally consistent with those given by σ ϕ , particularly in the middle-high-latitude region. However, the analysis on the distribution of σ ϕ for different ranges of ROTI shows ROTI cannot achieve accurate scintillation monitoring at the epoch level in all selected stations. The main outcomes of this paper are of importance in guiding the reasonable application area of ROTI and developing a high-latitude ionospheric scintillation model based on geodetic receivers.

Absorption level by riometer was estimated at high-latitudes during four moderate magnetic storms that occurred in 2018 and were similar by several features. The data of riometer absorption at 30 MHz was obtained from Sodankyla Geophysical Observatory in Finland (67.36°N, 26.63°E). Particle precipitations were estimated by POES satellite data. According to our results, the character of development of the magnetic disturbance and the similarity/difference of Space Weather parameter variations (IMF magnitude, solar wind parameters, Dst variation) did not played the leading role in the absorption peak value. The absorption level in the auroral oval during the considered similar moderate magnetic disturbances depended on the combination of factors: simultaneous electron bursts of particular energies, the number of precipitating particles in these bursts and the moment of the storm at which such precipitation bursts occurred. The highest absorption was caused by the large electron precipitations with energies of >40 keV and >130 keV that occurred just after the maximal storm development at the very beginning of the recovery phase of the storm.

This study provides insight into the effect of eccentric loading on soil arching. A numerical trapdoor model was developed using the discrete element method to investigate the evolution mechanism by considering the magnitude of the surcharge and the deviation distance. The parameters were validated using laboratory results. The numerical results showed that the Ground reaction curve (GRC) on the trapdoor could be divided into two categories. GRC type I included stages of initial soil arching, maximum soil arching, load recovery, and an ultimate stage. For GRC type II, the ultimate stage was replaced by a declining stage. The minimum soil arching ratio increased with the increasing surcharge, but decreased with the increasing deviation distance within 0.75B (B is the trapdoor width). The vertical displacement field inclined as the load deviated from the centered position, transforming from a trapezoid to a quadrilateral. The soil arching effect was degraded by the surcharge.

Yearly sunspot cycle 24 (SC24) activity reached a minimum in December 2019. Timeline for SC25 is explored with data for sunspot numbers (SSNs) and geomagnetic indices (aa/Ap) using our time-tested heuristic methodology not based on any model. We infer SC25 may be as active as SC24, reaching its peak (Rmax) in February 2024 ± 6 months, ruling out Dalton-like minimum in 21st century as well as McIntosh et al. [2020] forecast that “SC25 could have a magnitude that rivals the top few since records began.” Wide range of SC25 forecasts challenges our understanding of solar dynamo operation and reliability of future long-term space weather / climate forecasts. We cannot anticipate whether SC25 may have multiple peaks; no theory is tuned to predict fine structure of a SC. During ascending phase of SC24 a CME from the Sun barely missed the Earth. A direct hit by it could have caused damage of trillions of dollars, shutting down power grid and rendering satellites blind.

Aerodynamic roughness length ( z 0 m ) is a key parameter in the characterization of land surface turbulent heat fluxes and widely used in many surface and climate-related process models. The global products of time series of z 0 m at finer spatio-temporal resolution, however, have never been publicly available. Here we presented a practical method for global estimates of 500 m daily z 0 m with a combination of machine learning techniques, wind profile equation, observations from 273 sites and MODIS remote sensing data. Results showed that the random forest (RF) model outperformed the deep neural network (DNN) and convolutional neural network (CNN) models, and it could well reproduce the magnitude and temporal variability of daily z 0 m at almost all sites for all land cover types. In the validation of the RF-estimated daily z 0 m with the in-situ observations, the root mean square error (RMSE) varied between 0.02 m and 0.09 m, the mean absolute error (MAE) varied between 0.01 m and 0.05 m and the coefficient of determination ( R 2 ) was 1 for medium-to-high canopy shrublands, savannas and forests; for short-canopy croplands, grasslands and wetlands, the RMSE and MAE were 0.02 m and 0.01 m, respectively, and the R 2 varied between 0.94 and 1. Compared to the Climate Forecast System Version 2 (CFSv2, 0.3°/monthly) and ECMWF Reanalysis v5 (ERA5, 0.25°/monthly) products in 2019, the RF-estimated z 0 m was found to have the similar global spatial pattern but significantly larger temporal variability, and it also showed a higher and lower global mean of z 0 m over forests and non-forests, respectively. The RF-estimated z 0 m displayed a higher temporal variability but a similar global spatial pattern of this variability compared to the CFSv2, whereas the ERA5 z 0 m product exhibited almost no temporal variability except for grasslands and croplands. This study is beneficial for improving the simulation of the momentum, water and energy transfer between land and atmosphere and helping boost the development of high-resolution land surface models and Earth system models.

It is known from the literature that solutions of homogeneous linear stable difference equations may experience large deviations, or peaks, from the nonzero initial conditions at finite time instants. While the problem has been studied from a deterministic standpoint, not much is known about the probability of occurrence of such event when both the initial conditions and the coefficients of the equation have random nature. In this paper, by exploiting results on the volume of the Schur domain, we are able to compute the probability for deviations to occur. This turns out to be very close to unity, even for equations of low degree. Hence, we claim that “solutions of stable difference equations probably experience peak”. Then, we make use of tools from statistical learning to address other issues such as evaluation of the mean magnitude and maximum value of peak.

Background/Purpose This study measured the acceleration magnitude using a dummy model filled with various air-material ratios to elucidate the mechanism of resonance effect on ocular vestibular-evoked myogenic potential (oVEMP). Methods With the percentages of air volume altered by filling various materials (water, glycerol, or ethanol) in an acrylic-made hollow spherical model, a minishaker was utilized to deliver vibration stimuli to the model. Then, acceleration magnitude of each model was measured. Results Since the air was most occupied at the upper part of the model (z-axis), acceleration magnitude along the z-axis was selected for comparison. An increasing trend of the z-axis acceleration magnitude ranging 0.110–0.759 g was identified in air–water model with air volume percentage ranged 40–100%. On the other hand, a significant increasing trend of acceleration magnitude along the z-axis (0.157–0.759 g) was noted in air-glycerol model with 80–100% of air volume. While in air-ethanol model, a significant increasing trend in acceleration magnitude along the z-axis ranged 0.121–0.759 g correlating with 40–100% of air volume. Conclusion The mechanism for eliciting oVEMP is via the first-order bone vibration coupled with the second-order resonance effect. Both percentage of air volume (i.e. frontal sinus) and density of filling media (i.e. skull property) may contribute to the resonance effect, which then increases the acceleration magnitude so as to enhance the elicitation of oVEMP.

Estimating ground motion characteristics at various locations as a function of fault characteristics is useful for the proper damage assessment and risk mitigation strategies. This paper explores the application of machine learning approaches to predict peak ground acceleration (PGA) and peak ground velocity (PGV) using New Zealand’s strong motion data. Five machine learning algorithms, namely linear regression, kNN, SVM, Random Forest, and XGBoost, are used in this study. Using the New Zealand flat-file database, the geometric mean of the peak ground motion parameters is used as predictor variables in training the machine learning algorithms. The performance of the chosen algorithms and how they work on PGV and PGA are discussed. The best prediction for PGA is obtained using random forest but for PGV XGboost worked best. The relative importance of various features in the flat file is also presented for the best-performing machine learning algorithm. Although the magnitude of an earthquake is found to be most influential for PGV, rupture distance showed the highest impact for PGA. Finally, the predictions are also explained using SHApley Additive exPlanations (SHAP) for the overall dataset as well as on a sample by sample basis, for a few samples. Pairwise dependency of some features with the highest feature importance is also presented using SHAP.

Noise and whole-body vibration measurements were made in a Viking military vehicle to determine the variation that should be expected during repeat measures, the effect of speed (up to 60 km/h in 5 km/h increments), and during travel over different types of terrain (comprising concrete road, gravel track and rough cross-country). Measurements were made at various crew positions (including the driver and commander) in both the front and the rear cabs in the vehicles. Three translational axes of vibration were measured in each seat. Two speeds were investigated over road (35 km/h and 55–60 km/h) and gravel (20 km/h and 35 km/h) surfaces. The effect of varying speed of the vehicle on the measured noise and vibration magnitudes was also investigated. The highest sound pressure level (LAeq) of 104 dB(A) was measured at the commander’s standing position during travel over concrete road at 55 km/h. Higher noise levels occurred for a standing commander compared with when sitting on the seat. A maximum single axis frequency-weighted vibration magnitude of 1.0 m/s2 r.m.s. was measured on the driver’s seat during travel over track at 35 km/h. Higher vibration magnitudes occurred during travel over track compared with travel over road. Both noise and vibration exposure of crew within the Viking vehicle increased with increasing speed of the vehicle.

Diverse studies about equatorial plasma bubble structures and their relation with ionospheric scintillation have been performed in the last decades. Among many findings, the investigations usually reported dominant plasma bubble eastward velocity with a magnitude of few tens of m/s and larger amplitude scintillation for transionospheric signals aligned with these depleted structures. However, an uncommon long-lasting event with negligible average zonal drift prevailing for hundreds of minutes was registered over the Brazilian region, allowing a case study of the scintillation pattern under this particular condition. Data from ionosondes, all-sky imager (6300 A filter), geostationary satellites and Global Navigation Satellite System were used here, covering the eastern portion of the Brazilian ionosphere. The results show that the scintillation was less intense than in other nights around the event, suggesting that larger plasma density gradients and sequential bubble structures seem to cause more severe scintillation scenario than the alignment condition alone, even though the last also contributes to worsen the scintillation effects. Regarding the stagnant bubble pattern, the results suggest prevailing E region Hall conductivity and equatorward wind as potential agents.

In the present paper, we investigate the electron density observations from the Langmuir probes (LPs) onboard low Earth orbiting (LEO) Swarm satellites. To accentuate its employability in model improvements, we compared the extracted F2 region critical electron density (foF2) and its corresponding altitude (hmF2) with the Digisonde observations and IRI-Plas 2017 model estimations at eight worldwide Digisonde locations during the year 2020. We attempted to visualize the discrepancy in magnitude between Swarm observation and IRI-Plas 2017 by independent simulation and then optionally ingesting the Digisonde foF2 and hmF2 parameters into the model. The results show that during nighttime, Swarm LP measured electron density model overestimates the IRI-Plas 2017 modeled electron density for all the stations. To confirm the above results, a comparison analysis has been performed for the Ne-Swarm A and Swarm B observations with that of IRI-2016 simulated output keeping the topside sub model as NeQuick along with other default options. The results show that Ne from Swarm A and Swarm B is higher than IRI-2016 estimations during the nighttime with the ratio ranging from 1 to 5 whereas during the daytime the ratio remains 0 to 1. This confirms that Swarm Ne observations have significantly higher values during nighttime over global region, reinforcing further studies on the surged nighttime variables. It has been also observed that there is no latitudinal disperency between Swarm and IRI-Plas 2017 modeled or IRI-2016 modeled observations.

Underground tunnels have offered a quick and cost - effective alternative for storage, traffic, and transportation in many countries. Due to intensive and more frequent occurrences of worldwide terrorism attacks on urban tunnels, there is a need to develop a methodology for designing underground structures that can withstand such attacks [14] . Therefore, in the present study, the physical modeling of D-Shaped shallow tunnels is carried out to understand tunnel behavior when subjected to a high rate of impact loading (projectile). To understand the tunnel deformation behavior, an extensive experimental investigation is performed on the physical model of the tunnel in synthetic rockmass subjected to impact loads. For rock-tunnel modeling, three different cover depths are considered. The impact loads of varying magnitude are applied at the center using drop hammer equipment. The deformation of the tunnel crown is measured along the tunnel length by means of a linear variable differential transducer (LVDT). Further, the finite element method based numerical investigation is carried out by using Abaqus/CAE numerical tool. The validation of the numerical model is performed by using the experimental results. It is found that the cover depth plays a vital role in determining the overall stresses and deformation when the tunnel is subjected to either static or dynamic loading. From the experimental and numerical investigations, it has been observed that the tunnel with the lowest cover depth experience excessive deformation, and the zone of influence, i.e., area through which crack propagates, is less. The maximum deformation along the tunnel length is observed in the D-Shaped shallow tunnel as compared to the Circular Shape tunnel.

Stochastic reconstruction (SR) is one of the most usable molecular reconstruction approaches applicable to heavy petroleum cuts, using statistical distribution to describe the structure attribute of molecules in a mixture. Suitable values for distribution parameters are estimated during an optimization process on the base of mixture characterization data. This study focuses on searching the connection between the parameter of structure attribute distributions and different types of experimental data, used for hydrocarbon mixture characterization. An algorithm has been introduced that allows to determine which types of analytical data affect the distribution of structure attributes based on testing statistical hypotheses. The core idea is looking for a significant correlation between calculated properties and distribution parameters, and then comparing the magnitude of parameter impact with measurement precision. It was shown that different types of analytical data can affect different parameters of the reconstructed composition: distillation curve data is the main source of information about distributions variance, while elemental analysis and PNA helps determine mean values for various structure attributes; information concerning the number of branches in molecules are strongly connected with 13C NMR data.

Deep-water bridges located in a V-shape canyon may suffer from spatially varying ground motions due to the canyon topography. This paper focused on the effect of canyon topography on the seismic responses of a deep-water continuous rigid-frame bridge that crosses a V-shape canyon. The ground motions in three example sites with different topography conditions were simulated by the numerical spectral element method. A database with one hundred point-sources considering the uncertainties of seismic magnitude and source location was sampled and adopted to simulate the seismic waves propagating from the source to the bridge site. Nonlinear seismic response analyses of the example deep-water bridge were performed under the simulated spatially varying ground motions considering the hydrodynamic added mass on the piers. The effects of the canyon topography on the seismic wave field, peak ground acceleration at bridge foundations, and seismic responses of the bridge were analyzed. According to the example studies, the canyon topography induces a significant spatial variation of the ground motions for the bridge in the canyon. Compared with the canyon topography, the influence of water within the canyon on the ground motion is slight. Neglecting the effect of canyon topography leads to the inappropriate assessment of the seismic fragility of the deep-water bridge in both component and system levels.

The present study reports the variations in bottom-side thickness (B0) and shape (B1) parameters from ionospheric measurements of Digisonde Portable Sounder, DPS-4 installed at Multan (geog coord 30.18°N, 71.48°E, dip 47.4°) during the deep solar minimum between solar cycles 23/24 i.e., 2008–09 as a continuation to our previous work (Ameen et al., 2018). We have found that B0 has peak values during daytime whereas, B1 exhibits nighttime peaks, with both parameters showing a diurnal pattern. Seasonally, B0 showed annual trend with maximum values during summer and the least values in winter. B1 has the converse seasonal behaviour with respect to B0. These electron density profile parameters have been compared with International Reference Ionosphere (IRI-2016) to check the performance of three available options namely, ‘Gul-1987’, ‘Bil-2000’ and ‘ABT-2009’. The least Root Mean Square Error (RMSE) values with respect to the three options show that ABT-2009 estimated seasonal B0 and B1 with greater confidence as compared to other two options. For day and nighttime values of the parameters, no specific model may be declared the best predicting B0 and B1 for the period under study. Much of the factors that influenced the behaviour of hmF2 over Multan (Ameen et al., 2018) seem to be affecting the magnitude of B0 including the post-sunset peak in winter. The present study may be helpful in updating sub-model ABT-2009 of IRI for better reconstruction of bottom-side profile over Multan.

This study extends the generalized true random-effects model to account for spatial dependence in persistent and transient inefficiency. For this purpose, a model with spatially autocorrelated persistent and transient inefficiency components is specified. Additionally, spatial dependence is also modeled in the noise component to account for uncontrolled spatial correlations. The proposed model is applied to a panel dataset of Wisconsin dairy farms observed between 2009 and 2017 and estimated using Bayesian techniques. Apart from the traditional output-input quantities, the utilized dataset also contains information on the exact location of farms based on their latitude and longitude coordinates as well as on environmental factors. The empirical findings suggest low levels of both persistent and transient inefficiency for farms. Additionally, all components exhibit spatial dependence with its magnitude being more than double for persistent inefficiency.

Based on the known fault distribution in Sichuan-Yunnan region (SYR), a rigid Euler rotation model is constructed by using GPS velocities (1998 ~ 2016) after excluding the stations near the fault boundaries and simultaneously a translation-rotation-strain model is constructed by using almost all GPS velocities to calculate three periods strain rate fields (2008.6 ~ 2010.4, 2010.5 ~ 2013.4 and 2013.5 ~ 2016.12) after Wenchuan earthquake. The results show that: (1) the strike-slip activity is the most common trends for the regional faults. The Xianshuihe-Xiaojiang fault, the Lancangjiang-Weixi-Weishan-Wuliangshan fault and the Longmenshan fault are the most active in the whole SYR, and the dislocation rate is more than 15 mm/a, and the trend of activity gradually decreases from the northwest to the southeast. (2) The different activity rates of the faults in the study area indicate that some of the eastward extrusion of the Tibet Plateau is absorbed and adjusted by the inside faults, and it is not a few large strike-slip faults. (3) Through the analysis of three periods’ grid velocity fields, we found that the movement rates of the Bitu section of Lanchangjiang fault, the Northwestern section of Weixi-Weishan fault and the Nujiang fault after Wenchuan earthquake are larger than that after Yushu and Ya’an earthquake, and the difference is about 8 mm/a. Besides, the activity rate of Northwestern section of Longmenshan fault after the Wenchuan earthquake is larger than that after the Ya’an earthquake, although the two epicentres distances are relatively close. (4) The strain rate fields and surface expansion rates show that the high value area is mainly distributed at or around the intersection among some fault zones and its surroundings, and the maximum area is mainly located at some long and deep fault zones such as the Longriba fault, the Longmenshan fault zone, the Ganzi-Yushu fault and the Xianshuihe, and the magnitude is about 35 ~ 50 nanstrain/a. The research should provide fundamental material for the study of crustal stress variation and earthquake prediction in Sichuan-Yunnan region.

To analyze the influence of a curved ceiling and fire location on the combustion characteristics in a utility tunnel, the burning rate and temperature profile produced by a pool fire beneath a curved ceiling were investigated experimentally and theoretically. The results showed that oxygen supply and heat feedback from the surrounding form a competitive mechanism, determining the evolution of the burning rate. A qualitative analysis was performed to elucidate this competitive mechanism. With the fire source moving close to the sidewall, the positive influence from the heat feedback is is gradually compensated for by the negative influence from oxygen supply limitation. Moreover, it was inferred that the magnitude of decline of the burning rate near the wall has a positive correlation with heat release rate of the fire source. A characteristic inclined angle was defined to replace the changing angle of the curved ceiling along the ceiling jet path. Based on the definition of the characteristic ‘inclined angle’ concept, the relationship between the temperature profile beneath the curved ceiling centerline, tunnel height and horizontal position from fire source was unified by an empirical model. The maximum temperature delay beneath the curved ceiling centerline produced by the pool fire was analyzed by radial flow and one-dimensional flow. The proposed models for radial flow and one-dimensional flow were validated and could effectively predict the maximum temperature delay, which can be applied in utility tunnel’s fire protection engineering.

International audience; The estimation of tropospheric gradients in GNSS data processing is a well-known technique to improve positioning precision.To study the correlation between the tropospheric gradients and the topography, we computed Zenith Wet Delay (ZWD) and tropospheric gradients using the GIPSY-OASIS II SOFTWARE from 2 years of GPS observations recorded at 52 worldwide permanent stations, focusing on regions with significant relief. We observe that gradient directions are stable over time and point towards the relief for most of the considered stations. Based on these results, we discuss the physical meaning of the tropospheric horizontal gradients and we investigate why gradients have this particular direction for stations located nearby high mountains. The GPS stations were selected and classified into four main categories: stations close to a mountain range or an isolated mountain (class 1 and 2), stations surrounded by isolated mountains in several directions or in all directions (class 3 and 4). The correlation between the gradient direction and their magnitude with respect to mountain slopes was analysed. A very clear correlation appears for stations of classes 1 and 2 whereas no correlation is obvious for stations of classes 3 and 4. For 89% of stations in classes 1 and 2, a relevant correlation appears, varying between 0.4 and 1. For 64% of stations in classes 1 and 2, a relevant correlation appears, varying between 0.6 and 1. Horizontal gradients estimation show very significant amplitude and a stable direction all along the year, this main direction is most of the time pointing towards the direction of mountains. This behaviour can be explained by a vertical shift of the tropospheric layer due to the presence of mountains, close to the station and up to the maximum distance of 60 km from the station. This orientation does not seem to depend on seasons because no annual or bimonthly means variations appear for all stations. Moreover diurnal variations do not appear on the spatial distribution of the gradients and results are similar for neighbouring stations, separated by few km, which show that local effects such as multipath propagation have influence.

In this paper, we have considered a two-phase flow in a groovy curved channel. The fluid contains a uniformly distributed small particles and the flow is generated by a transient pressure gradient along the grooves. The governing equations describing the flow in the groovy curved domain are developed and the analytical solution of the complex flow field is determined using domain perturbation method. The effect of the particles on the flow is discussed through the particle relaxation time relative to the flow characteristic time. It is found that the fluid and particle velocities depend on the magnitude of particle relaxation time relative to the flow characteristic time. The effect of the grooves on the transient flow is examined in the presence of the fluid-particle interactions, and the associated results have been reported. The results are further compared with those of a two-phase flow in a smooth curved channel and a particle-free flow in a groovy curved channel, which are special cases of the present study.

This study focuses on the changes in wave energy in response to tidal currents in the western sea of Jeju Island where high-energy wave conditions along with strong tidal currents are usual. Here, an ocean-wave coupled modeling system was used to investigate the effect of tidal currents on the wave energy condition. A comparative experiment with and without tidal currents shows that the current largely affects wave energy in terms of the wave spectrum as a response to the relative direction between waves and currents. When the direction of the tidal current is the same as that of wave propagation, the magnitude of wave height is reduced with energy transfer from shorter periods of 7–9 s to longer periods of 10–12 s, resulting in a decrease (increase) of shorter (longer) wave energy. This reaction is reversed when the tidal current flows in a direction opposite to that of wave propagation. The uncoupled model tends to overestimate/underestimate the wave energy during the ebb/flood tides when the waves follow/oppose the currents by approximately 25%. This study demonstrates that ocean-wave coupling is capable of improving model wave conditions, and therefore, this model is useful for estimating potential wave energy resource and candidate sites.

The Langshan Piedmont fault (LPF) is an active Holocene normal fault that borders Langshan Mountain and the Hetao Graben in the northwest of Ordos Block of China. In this study, paleoseismic trenching was undertaken at three sites and 11 fault outcrops are well exposed. The results show that eight paleoearthquake events occurred on the LPF since 43 ka BP, and six paleoearthquake events are complete since 14 ka BP, the latest event is 2300–2400 a BP; the LPF has the characteristic of quasi-periodic recurrence and the average recurrence interval is 2350 years. Therefore, there is a high probability that the LPF will have another earthquake. The vertical activity rate of the LPF is ~1.12 ​mm/yr since Holocene, and ~0.77 ​mm/yr since 14 ka BP. In this study, it is considered that the LPF is mainly characterized by simultaneous rupture of the whole segment. The vertical displacement of the paleoearthquake events is 0.8–2.5 ​m and the corresponding maximum paleoearthquake magnitude is M 7.4. The seismic hazard of Langshan area should not be ignored. The buildings in Langshan area, especially Wulatehouqi and Qingshan town, should be able to withstand a magnitude 8 earthquake.

This study focuses on the assessment of the seismic performance for a 12-story high reinforced concrete structure situated in Bucharest, Romania. The structural system is common for many newly built office buildings in Bucharest and it consists of a flat slab with columns and thick reinforced concrete core walls. The seismic performance of the structural system is evaluated using ground motions with considerable long-period spectral amplifications, that are characteristic to Bucharest area during large magnitude Vrancea intermediate-depth earthquakes. The building is the first office building having a flat slab structure with core walls designed for the seismic conditions of Bucharest which is evaluated according to US Resiliency Council criteria and according to recent criteria proposed by Italian Guidelines. The results of the seismic rating show that it can be classified as a 3-stars for the safety criterion and as a 4-stars one for both the recovery time and repair cost criteria according to US Resiliency Council criteria. Moreover, the building can be graded as a class A one based on the criteria from the Italian Guidelines.

The direction and magnitude of a solar sail acceleration are strongly related. For this reason, once the characteristic acceleration has been fixed, it is not possible to modulate the acceleration in a particular direction. In this work, a semi-analytical switching control law is derived, enabling a solar sail to emulate a smaller effective characteristic acceleration (without changes in geometry or optical properties); by periodically changing the pitch (cone) angle of the sail, in average over time, the acceleration produced by the sail matches exactly (in both direction and magnitude) that of a “smaller” sail. The range in which this is possible is determined, and the limitations on this range due to the size difference is computed. The method is validated on optimal Earth-Mars trajectories.

The Sutlej river, one of the important tributaries of the Indus river, debouches into the Punjab-Haryana plains and makes a conspicuous change in its flow direction i.e., from southwest to west. This anomalous flow of the Sutlej river has given rise to a large interfluve between the Indus and Ganga river systems, in which an ephemeral Ghaggar river flows towards southwest that terminates inland. This study investigates the large interfluve between the Sutlej and the Yamuna rivers for its drainage reorganization including the westward deflection of the Sutlej river, using landforms and stream orientation analysis. The drainage network in the area can be divided into two orientation domains - west flowing and south-west/south flowing. Statistical and vector analysis of around 600 drainage vectors (including paleochannels and modelled flow vectors) and more than 9000 slope vectors indicate that the present-day drainage networks and their directivity vary with respect to the paleo-drainage networks as well as the modelled flow patterns. Regional slope deviatory and slope parallel channels point towards a shift of the Sutlej river from south to west in multiple stages. It is suggested that the westward avulsion of the Sutlej river is primarily driven by tectonics of the frontal zone, aided possibly by high magnitude extreme hydro-meteorological events.

Various information-theoretic divergences have been proposed for the cost function in tasks such as matrix factorization and clustering. One class of divergence is called the Beta divergence. By varying a real-valued parameter β , the Beta divergence connects several well-known divergences, such as the Euclidean distance, Kullback-Leibler divergence, and Itakura-Saito divergence. Unfortunately, the Beta divergence is properly defined only for positive real values, hindering its use for measuring distances between complex-valued data points. We define a new divergence, the Complex Beta divergence, that operates on complex values, and show that it coincides with the standard Beta divergence when the data is restricted to be in phase. Moreover, we show that different values of β place different penalties on errors in magnitude and phase.

Pitch angle greatly affects the performance of VAWT. Aiming at the maximum value of CT, this study first obtains the theoretical optimal angles of attack, i.e., 17.7° and −18.4° in upwind and downwind zones. A 2.5D model is simulated using Fluent to determine the magnitude and direction of induced velocity, and an initial pitch angle adjustment law is obtained combining the proposed local TSR. Compared with a prototype wind turbine, CP is increased by 2.69% after applying the initial adjustment law. The fitting curve angle δ at the abrupt part of pitch angle is analyzed. The smaller the angle δ is, the more evident the performance improvement of VAWT becomes. CP is increased by 11.68% when the angle is δ = 0°. On this basis, the adjustment law corresponding to δ = 0° of 100°

Tropospheric delay is one of the major sources of error in VLBI (Very Long Baseline Interferometry) analysis. The principal component of this error can be accurately computed through reliable surface pressure data —hydrostatic delay— yet there is also a small but volatile component —wet delay— which is difficult to be modelled a priori. In VLBI analysis, troposphere delay is typically modelled in the theoretical delays using Zenith Hydrostatic Delays (ZHD) and a dry mapping function. Zenith Wet Delay (ZWD) is not modelled but estimated in the analysis process. This work studies inter alia the impact of including external GNSS estimates to model a priori ZWD in VLBI analysis, as well as other models of a priori ZWD. In a first stage, two different sources of GNSS troposphere products are compared to VLBI troposphere estimates in a period of 5 years. The solution with the best agreement to VLBI results is injected in the VLBI analysis as a priori ZWD value and is compared to other options to model a priori ZWD. The dataset used for this empirical analysis consists of the six CONT campaigns. It has been found that modelling a priori ZWD has no significant impact either on baseline length and coordinates repeatabilities. Nevertheless, modelling a priori ZWD can change the magnitude of the estimated coordinates a few millimeters in the up component with respect to the non-modelling approach. In addition, the influence of a priori ZWD on Earth Orientation Parameters (EOP) and troposphere estimates —Zenith Total Delays (ZTD) and gradients—has also been analysed, resulting in a small but significant impact on both geodetic products.

Intractable delays occur in air traffic due to the imbalance between ever-increasing air traffic demand and limited airspace capacity. As air traffic is associated with complex air transport systems, delays can be magnified and propagated throughout these systems, resulting in the emergent behavior known as delay propagation. An understanding of delay propagation dynamics is pertinent to modern air traffic management. In this work, we present a complex network perspective of delay propagation dynamics. Specifically, we model air traffic scenarios using spatial-temporal networks with airports as the nodes. To establish the dynamic edges between the nodes, we develop a delay propagation method and apply it to a given set of air traffic schedules. Based on the constructed spatial-temporal networks, we suggest three metrics—magnitude, severity, and speed—to gauge delay propagation dynamics. To validate the effectiveness of the proposed method, we carry out case studies on domestic flights in the Southeastern Asia Region (SAR) and the United States. Experiments demonstrate that the propagation magnitude in terms of the number of flights affected by delay propagation and the amount of propagated delays for the US traffic are respectively five and 10 times those of the SAR. Experiments further reveal that the propagation speed for U.S. traffic is eight times faster than that of the SAR. The delay propagation dynamics reveal that about six hub airports in the SAR have significant propagated delays, while the situation in the United States is considerably worse, with a corresponding number of around 16. This work provides a potent tool for tracing the evolution of air traffic delays. Civil Aviation Authority of Singapore (CAAS) National Research Foundation (NRF) Accepted version This work was supported by SUG Research Grant M4082126.050 by School of Mechanical and Aerospace Engineering (MAE), Nanyang Technological University (NTU), Singapore and NTU-CAAS Research Grant M4062429.052 by ATM Research Institute, School of MAE, NTU, Singapore.

MAGDAS PEN was established on 19th September 2019 as one of the MAGDAS observatory arrays located at Universiti Sains Malaysia (USM) (5.15°, 100.50°). The main objective of the MAGDAS project is to monitor global electromagnetic and the ambient plasma density in the geospace environment. This installation has contributed to a better understanding of the Sun-Earth coupling system. This paper presents the installation process of one of the MAGDAS magnetometers named YU-8 T magnetic sensor and provides a preliminary analysis of geomagnetic HDZ components amplitude-time that was observed at PEN station. A one-month HDZ-geomagnetic field data was processed from 1st November to 30th November 2019. The daily variations with a consistent pattern in delta H geomagnetic field components are observed throughout the day with eastward electric field effects that are observed during solar peak hours. The delta H-component gradually increases around 0700LT and reaches the maximum reading at 1300LT with a range of value ~ 40-70nT. The value slowly decreases that started from 1400LT until the night time. The reading during the night time shows a constant variation with magnitude varies in between −10nT to + 10nT. The average H-component value of the night time is used as the baseline for the observation system. Overall, the observed trends portray a good sign of solar quiet field and Sq with no solar-terrestrial disturbances.

Chong (1995) and Bai (1997) proposed a sample-splitting method to estimate a multiple-break model. However, their studies focused on stationary time series models, in which the identification of the first break depends on the magnitude and the duration of the break, and a testing procedure is needed to assist the estimation of the remaining breaks in subsamples split by the break points found earlier. In this paper, we focus on nonstationary multiple-break autoregressive models. Unlike the stationary case, we show that the duration of a break does not affect whether it will be identified first. Rather, it depends on the stochastic order of magnitude of signal strength of the break under the case of constant break magnitude and also the square of the magnitude of the break under the case of shrinking break magnitude. Since the subsamples usually have different stochastic orders in nonstationary autoregressive models with breaks, one can therefore determine which break will be identified first. We apply this finding to the models proposed in Phillips and Yu (2011) and Phillips et al. (2011, 2015a, 2015b). We propose an estimation procedure as well as the asymptotic theory for the model. Some extensions to more general models are provided, and the hypothesis test with the null hypothesis being the unit root model is examined. Results of numerical simulations and an empirical study are given to illustrate the finite-sample performance.

Ionospheric response during the annular solar eclipse of June 21, 2020, has been examined in terms of the Total Electron Content (TEC) obtained from six Global Positioning System (GPS) receivers positioned in the Chinese-Taiwanese region. We have shown TEC variation from satellites designated by PRNs (Pseudo-Random Noise code) 2, 6, and 19. PRN wise TEC trend was observed to depend upon satellite-pass trajectory to the receiver's location during the eclipse period. A time lag of ~15–30 min is also observed in maximum TEC decrement after the phase of maximum eclipse. Instead of the percentage of eclipse magnitude, a reduction in TEC is seen more for the station for which the orbital track of respective satellites was in closer view relative to receivers for more hours of eclipse window. Additionally, the eclipse day diurnal variations are compared with the pre-eclipse day TEC trend, and observed results show a clear decrease in TEC values at all chosen stations after the eclipse onset then reached the lowest value a few minutes afterward the maximum eclipse phase.

Mapping and monitoring of the glacier changes over different regions of Earth surface is a challenging task due to regional rugged topography and climate conditions. This study focused on the monitoring of snow or ice cover changes over Chhota-Shigri glacier, Western Himalaya, India. A subpixel-based change detection (SCD) approach is proposed, aiming to identify the transition zones (mixed pixels) between the two class categories. The SCD approach involves the integration of subpixel classification and change vector analysis (CVA) to define the changes in the form of magnitude and direction between two multitemporal dates at the subpixel level. To check the efficacy of proposed SCD, experimental outcomes have also been compared with existing neural-network (NN) based SCD (NN‒SCD). The result analysis has shown that proposed SCD achieved better accuracy (84.80%) as compared to NN‒SCD (78.80%). In addition, a time series data was acquired using the Landsat series (Landsat 5, 7 and 8 as per availability) to perform the trend analysis over Chhota-Shigri glacier, during the period 2001–2019. This study offers the effective way of estimating the bi-temporal snow/ice changes especially over rugged terrains around the globe.

There was a shallow earthquake in the Central Sulawesi province of Sulawesi island of Indonesia with a moment magnitude (Mw) 7.5 on 28th September 2018 at 18:02:44 local time. The event was preceded by major foreshocks and followed by aftershocks of significant magnitude. The epicenter of the main shock was in the Donggala regency of Minahasa peninsula of Central Sulawesi, approximately 70 km from the provincial capital of Palu. The earthquake was caused by the tectonic movement of the left lateral Palu- Koro fault within the Molucca Sea microplate, triggering major geotechnical failure and structural damage in Palu city and Sigi regency. Thousands of people died or are still unaccounted for, and countless others were injured. Balaroa, Petobo, Jono-Oge and Sibalaya were the worst hit mainly due to large-scale flow-slides and mud flows. It was the first time that such large-scale flow failures were triggered by an earthquake, and that the failure of very gentle sloping ground swept away whole localities. The objective of this research was to provide insight into the scale of ground failure and other infrastructural damage caused by the event, especially in Jono-Oge area, where the flow distance was longest. The authors performed preliminary and detailed surveys in the area twice by conducting Portable Dynamics Cone Penetration Test (PDCPT), collecting disturbed and undisturbed samples and using aerial drone (UAV) photography. The findings of the reconnaissance survey are described here along with subsequent data interpretation. Finally, the mechanism of the flow-slides is discussed.

LiDAR (Light Detection and Ranging) remote sensing is the most popular technology delivering higher detailed information and accuracy. LiDAR data is majorly used for generating a high-resolution digital elevation model (DEM), which is one of the primary data for most of the remote sensing applications. DEM forms the basis to derive other terrain parameters that are important to understand the topographic variations for the majority of applications. This research work highlights the potential of airborne LiDAR data for the extraction of terrain parameters. The airborne LiDAR dataset used in this study is of the St. Petersburg region of Russia. Terrain parameters like digital surface model (DSM), bare earth model (BEM), slope, aspect, curvature and terrain ruggedness index (TRI) are estimated from the airborne LiDAR data. Ground control points surveyed using Differential Global Positioning System (DGPS) technique are used to assess the accuracy of the generated digital elevation model. An RMSE of 1.30 cm is obtained for the generated DSM with a maximum error of 3.5 cm magnitude. A complete analysis of derived parameters is done to observe the accuracy achieved.

A total of 160 earthquakes in North East Indian region and surroundings were analysed for earthquake precursor detection using GPS based Total Electron Content (TEC) estimation in the Ionosphere. TEC is very sensitive to short-term disturbances of a geomagnetic storm, solar flares and seismic activities. In the present study, TEC in the ionosphere was measured using dual-frequency signals from five GPS-based continuously operating reference stations/system (CORS) installed in North Eastern states of India. The abnormality in TEC variations was observed by constructing boundary limits using statistical method, the values crossing the limits being the anomaly. The results for Mw > 5 earthquakes such as Mw 5.5 Kohima Earthquake (July 14, 2012), Mw 6.8 Myanmar earthquake (November 11, 2012) and Mw 5.6 Kokrajhar Earthquake (June 28, 2015) covering North East India suggest TEC anomaly 10 days, 12 days and 13 days prior to the events. Analysis of 160 earthquakes suggests that the rate of success in TEC based anomaly detection for earthquake precursor increases with increase in Magnitude of the earthquakes. In average Mw 6 earthquakes could be fully detectable. Rate of success with reference to CORS were also computed and was found in the order of Cherrapunjee, Meghalaya > Madankamdev, Assam > Mohanpur, Agartala > Mawtawar, Meghalaya > Khanapara, Assam. Therefore present investigations confirmed TEC anomalies prior to earthquakes and present the expected rate of success, making it imperative to set up an automated system for real-time monitoring of TEC for Earthquake precursor detection and appropriate forewarning in near future.

At two-way stop controlled (TWSC) intersections drivers on minor stream are generally at risk because of the difficulty in judging safe gap between major stream vehicles. Any misjudgment by the driver while choosing gap may result in a collision with major stream vehicle. This paper provides important insights for determining and analyzing spatial critical gaps of drivers at high speed and medium speed TWSC intersections. The critical gap line (CGL) fitted for the accepted and rejected gaps using parametric (binary logit model-BLM) and non-parametric (support vector machines-SVM) techniques gives critical gap values at 15th, 50th and 85th percentile speeds. The evaluation of spatial critical gap with respect to major road vehicle (conflicting vehicle) speed makes it easier to understand the impact of variation in speed on spatial gaps accepted by the drivers on the minor road. The logit models developed revealed that the probability of accepting gap decreases with increase in the speed of the conflicting vehicle and it increases with increase in the distance of conflicting vehicle. The spatial critical gaps estimated using support vector machines were found in close approximation with those estimated using binary logit model. The study results showed that SVMs have very good potential to be an alternative tool for the estimation of driver's critical gap. The spatial critical gaps corresponding to 15th, 50th and 85th percentile speeds for medium speed intersections were 32 m, 38 m and 46 m respectively and for high speed intersections these values were 64 m, 76 m and 104 m respectively. The increase in the magnitude of gap value with respect to the percentile speed clearly states the effect of speed on spatial gaps. The insights from the study can be used to suggest various measures to improve the safety of crossing drivers at uncontrolled intersections.

The focus of the present study is to estimate the active surface deformation/displacement affecting the landscape of the eastern Kachchh basin with a particular emphasis on the Wagad, Khadir Island, Bela Island, Chorar Island, and adjoining regions by implementing Differential Interferometry Synthetic Aperture Radar (DInSAR) technique using ENVISAT and SENTINEL-1A radar imagery. To evaluate the deformation pattern using DInSAR, we used ENVISAT-ASAR 2003 to 2005 and 2006 to 2009 data products and SENTINEL-1A data set of 2018–2020. The cumulative displacement of 0.2–0.3 cm for the period of 2003–2005 and 0.19–0.22 cm for the period of 2006–2009 has been observed for the South Wagad Fault region. Similarly, the results acquired from SENTINEL-1A data set revealed a cumulative displacement of 0.16–0.18 cm for the period of 2018–2020. The Island Belt Fault zone shows 0.27 cm displacement, while it is 0.10–0.17 cm for the Gedi Fault zone. The rate of deformation estimated from the present study is well corroborated with the existing results of GPS driven uplift rates. The combined results of DInSAR and GPS indicate that the northern part of the Wagad region is deforming much faster than the south Wagad region. The displacement detected to the east of the epicentral zone of the 2001 Bhuj earthquake indicates the presence of a zone of weaker structures, which may trigger a large magnitude earthquake in the future. Our estimated results of the short-term ground displacement are well corroborated with the existing geological information. This ground displacement is attributed to the tectonic subsidence towards the eastern part of the South Wagad Fault region and within the wide zone of the Island Belt Fault and Gedi Fault zones. The areas with a high amount of displacement have experienced continuous seismicity during the last two decades in the Eastern Kachchh region and might encounter moderate to high seismicity in the near future. The results also provide a better understanding of the active surface deformation pattern taking place in the seismically sensitive eastern Kachchh region.

Dynamic identifier is developed for a nonlinear sine-Gordon model. It is shown that the spatially-varying magnitude of the sine-wise external force comes identifiable provided that the model is persistently excited by a nonzero input. The present investigation focuses on the case where the full state information is available for the measurement. Capabilities of the theoretical results obtained are numerically illustrated in the case study of a spatially-invariant plant parameter.

Chamoli district of Garhwal Himalaya is one of the highly seismically active region and probable zone for impending great earthquake in the CSG. In the present study, to understand the upper crustal anisotropy of Chamoli region, shear wave splitting (SWS) analysis is performed for local seismic events. For events > 2 M reported at Ghuttu station during the period Nov 2014 to JULY 2015, SWS parameters are measured. A considerable temporal difference in delay time was observed during the SWS study with respect to the 4.9Mw magnitude earthquake that occurred in the Chamoli region on 1st April 2015 at 21:23 hrs (UTC). A rise in delay time prior to the earthquake which decreases steadily over time is observed at GTU station. This decrease in delay time can be related to the region’s stress relief. The calculated average delay time (δt) is 3.83 ms/km and a maximum value of 5.37 ms/km for the earthquake of magnitude 4.9Mw. Sfast polarization direction range from N120° to N170° has been observed for the majority of the earthquakes. An average NW-SE orientation of the shallow subsurface micro-cracks along the ray path beneath the Chamoli region has also observed. Present study is a step towards earthquake precursory research in Garhwal-Kumaun region for monitoring of the state of accumulated stress. This study clearly demonstrate that SWS measurements for local earthquakes can be utilized for continuous monitoring of temporal variation in time delay (δt) and probably used for stress forecast for an impending earthquake.

A case of high magnitude chatter vibrations of a flexible tubular part is considered via dynamical modelling in time domain, in a delayed differential equation (DDE) framework. A ploughing term is introduced into the tool-workpiece interaction law. This term is based on a penalty-type law depending on the instant effective clearance angle. This ploughing interaction produces a vibration limiting mechanism featuring realistic maximum magnitudes, as compared to experimental measurements. It is also shown that in spite of interrupted surface pattern, the cut remains continuous under chatter. Furthermore, this model restitutes re-stabilisation at the exit of a stability lobe, with several instabilities occurring during the operation.