Strike Angle Research Articles

Intensive field measurements for characterizing the permeability and methane release with the treatment process of pressure-relief mining

Characterizing the permeability evolution and methane release is of great significance for the safe mining of the high gas outburst seams, as well as coal and gas simultaneous extraction. It contributes to reduce methane emissions from coal mining for greenhouse effect control. Theoretical analysis, laboratory testing, and numerical simulation are widely used methods to characterize the permeability and methane release with the treatment process of pressure-relief mining. However, these methods cannot fully reflect the complexity of filed practice. In this study, we report the effectiveness of protective coal seam (PCS) mining and the pressure-relief area in the protected coal seam (PDCS) based on detailed and integrated field measurements in a Chinese coal mine. To the best of our knowledge, it is the first time to measure the permeability coefficient and gas pressure evolution in the PDCS during the process of PCS longwall mining. The evolution of the permeability coefficient in the pressure-relief area during PCS mining can be divided into four stages: slowly decreasing, sharply increasing, gradually decreasing, and basically stable. The maximum permeability coefficient is 322 times of the initial value and stabilized at 100 times after the goaf compacted. The gas pressure evolution in the PDCS indicates that the strike pressure relief angle is 52.2° at the active longwall face zone, and 59.3° at the installation roadway side. The inclined pressure relief angles at the lower and upper sides of the longwall face are 75° and 78.9°, respectively. The residual gas content and gas pressure of the PDCS in the pressure-relief area are reduced to less than 6 m3/t and within 0.4 MPa, respectively. The field measurements further prove that pressure-relief mining can prevent coal and gas outbursts in PDCSs. The field observations in this paper can serve as benchmark evidence for theoretical analysis and numerical simulations, and also provide insights into realizing safety mining in similar conditions.

Overall subshear but locally supershear rupture of the 2021 Mw 7.4 Maduo earthquake from high-rate GNSS waveforms and three-dimensional InSAR deformation

An Mw 7.4 left-lateral earthquake hit Maduo County in Qinghai province, China, on 21 May 2021. In this paper, we combined the 1-Hz global navigation satellite system (GNSS) displacement waveforms, GNSS static offsets and the three-dimensional (3D) co-seismic deformation field from the interferometric synthetic radar (InSAR) measurements to estimate the source kinematics of this event. Our results reveal that there was about 160 km of surface ruptures with varying strike angles, and the earthquake propagated bilaterally, with the bulk of the slip formed to the southeast of the epicenter. Substantial slip occurred to a depth of ~6 km, and the estimated maximum slip was ~5 m. The source time function presents a ~ 35-s total duration with two peaks, and the total geodetic seismic moment is 1.61 × 1020 Nm (equivalent to Mw 7.4). The near-field high-rate GNSS waveforms inversion results indicate that this earthquake is an overall subshear but locally supershear rupture event. The preferred average rupture velocity is 2.8 km/s while the velocities to the southeast and northwest of epicenter are 3.8 and 2.2 km/s, respectively. Supershear enhanced ground motion and simulation using the 3D curvilinear grid finite-difference method shows the acceleration caused by the earthquake exceeded the building code limits for bridges that collapsed due to strong ground shaking. Furthermore, this earthquake increased the stress level of the Maqin–Maqu segment of the East Kunlun Fault, and was also responsible for an off-fault aftershock sequence at the northwest end of the earthquake rupture.

A theoretical model for 3D hydraulic fracture intersecting with natural fracture

Hydraulic fracturing has been widely applied to enhance the productivity of shale gas reservoir. Natural fractures and weak layers usually exist in the reservoir formation. There are generally three modes when a hydraulic fracture reaches natural fracture, namely crossing, opening and slippage. The complex fracture network can improve the efficiency of extraction. Several of 2D models have been developed to describe the behavior of hydraulic fracture intersecting with natural fracture, which usually ignore the effects of vertical stress and dip angle. To accurately predict the intersecting mode, a 3D fracture intersection model is proposed considering the critical fluid pressures. Predictions of the developed model show good agreement compared with the experimental data. It is noted that the distribution of intersecting modes depends on the in-situ stress, the properties of the formation, the coefficient of friction, the cohesion of natural fracture, the strike and dip angle of natural fracture. Sensitivity of the parameters in the developed model is investigated, which affects the redistribution of crossing, opening and slippage zone.

Does the Achilles Tendon Influence Foot Strike Patterns During an Exhaustive Run?

The study purpose was to investigate whether there is a relationship between the Achilles tendon (AT) length, moment arm length, and the foot strike pattern (FP) change during an exhaustive run (EXR) in nonrearfoot FP runners. Twenty-eight runners were recruited and divided into 2 groups (highly trained/moderately trained) according to their weekly training volume. Participants underwent the graded exercise test, the EXR with biomechanical analysis at the beginning, and at the end, and the magnetic resonance imaging scan of the AT. Correlations were used to assess associations between FP change (value of the difference between end and beginning) and the selected performance and AT variables. AT length significantly correlated with the FP change according to foot strike angle (r = -.265, P = .049). The AT moment arm length significantly correlated with the FP change according to strike index during EXR (r = -.536, P = .003). Multiple regression showed that AT length was a significant predictor for the FP change according to foot strike angle if the second predictor was the graded exercise test duration and the third predictor was training group association. These results suggest that a runner's training volume, along with a longer AT and AT moment arm appear to be associated with the ability to maintain a consistent FP during EXR by nonrearfoot FP runners.

Three‐Dimensional Magnetotelluric Inversion for Arbitrarily Anisotropic Earth Using Unstructured Tetrahedral Discretization

AbstractWe propose a new three‐dimensional anisotropic inversion scheme for magnetotelluric (MT) data. In this method, the earth is discretized into unstructured tetrahedral grids that can fit complex structures well, such as the earth topography and coastline. We use a 3 × 3 tensor to describe the anisotropic conductivity in the governing equation for MT inversions that can be simplified to three principal conductivities and three rotation angles. The edge‐based finite‐element (FE) method is adopted to do the forward and adjoint modeling to compute full impedance and sensitivity. To make the inversion flexible in the restoration of anisotropic and isotropic structures tendentiously, we add an additional regularization in the objective function, with its weight controlled by a distribution function. Before solving the inverse problem using L‐BFGS optimization, we add upper‐bound and lower‐bound constraints to the parameters to suppress the solution space. Four synthetic experiments are designed to test the resolvability and resolution for the six anisotropic parameters in the inversion. The results show that our inversion method can well recover the resistivity in the principal x and y directions and the strike angle γ. Finally, we apply our inversion algorithm to the USArray MT data with the aim to reveal anisotropic structure under Oregon State.

Clinical Features in Parkinson's Disease Patients with Hyperechogenicity in Substantia Nigra: A Cross-Sectional Study.

BackgroundTranscranial ultrasound (TCS) can be used to reveal structural changes in the substantia nigra (SN) and is a potential tool for the early diagnosis of Parkinson’s disease (PD). This study aimed to explore the relationship between substantia nigra hyperechogenicity (SNH) and the clinical features of PD patients.MethodsA total of 96 PD patients were included in our study. All patients were detected by TCS and divided into two groups: PD patients with SNH (PDSN+) and those with normal SN echogenicity (PDSN-). The Unified Parkinson’s Disease Rating Scale (UPDRS) and the Hoehn & Yahr stage were used to assess the extent of disease-related disability of the PD patients. Non-motor symptoms were evaluated by using several scales. The instrumented stand and walk test was performed on all subjects, and gait data were gathered using a JiBuEn gait analysis system.ResultsSeventy-five PD patients were successfully assessed by TCS. We found that SNH was associated with a higher UPDRS II scores (p = 0.028). In addition, compared with PDSN- group, the PDSN+ group exhibited more severe gait impairment, including increased variability in stride length (p = 0.042), decreased heel strike angle (p = 0.017), decreased range of motion of hip joints (p = 0.031), and a more asymmetrical walking pattern (p = 0.028).ConclusionOur study demonstrated that SNH significantly correlated with activities of daily living and gait impairment in Chinese patients with PD, suggesting the formation of SNH might be a dynamic biomarker reflecting disease severity.

Ancient structural inheritance explains gold deposit clustering in northern Perú

Abstract The punctuated distribution of major gold deposits along orogenic belts is poorly understood. In northern Perú, gold deposits cluster along trends that transect the subparallel Phanerozoic belts that accreted onto the western margin of the Archean–Proterozoic Amazonian craton. This suggests the influence of as yet unrecognized pre-Andean basement structures in controlling the localization of Phanerozoic deposits. We report the newly discovered Tomac ophiolite, which represents a missing link in tracing a cryptic basement collisional suture striking obliquely to the Peruvian Andes. The Tomac ophiolite signals the opening of a former Neoproterozoic ocean basin between the Amazonian craton and a continental ribbon of dispersed microterranes. Re-accretion of the continental ribbon resulted in the formation of a collisional belt between ca. 465 and 440 Ma. Rifting and re-accretion occurred parallel to the strike of the ca. 1400–1000 Ma Grenvillian-Sunsás orogen, indicating that structural corridors that transect the Andes at an oblique strike angle reflect inheritance of preexisting lithospheric weak zones. Our study demonstrates that Phanerozoic gold deposits in northern Perú cluster at the intersection between the newly defined basement suture and the superimposed Andean belt and associated well-documented cross faults. Gold mineralization was localized at ancient structural intersections, where enhanced permeability facilitated anomalous energy and mass transfer, promoting major ore accumulation during episodes of accretion.

Source Model for the 2022 Qinghai Menyuan Ms 6.9 Earthquake Based on D-InSAR

On 8 January 2022, an Ms 6.9 earthquake occurred in Menyuan County, Qinghai Province, China. This earthquake ruptured a patch of the Qilian-Haiyuan fault in the northeast margin of the Qinghai-Tibet Plateau. In order to understand the seismogenic structure of this earthquake and analyze the fault activity, we use differential synthetic aperture radar interferometry (D-InSAR) technology to obtain a complete co-seismic displacement field on the surface, and use pixel tracking algorithm to extract the trace of the ruptured fault. The slip distribution of the seismogenic fault was inverted using the steepest descent method, and the Coulomb stress change caused by the earthquake was also calculated. Surface deformation results show that the Menyuan earthquake produced obvious surface displacements in an area of 50 × 40 km2. The displacements are mainly distributed in the western segment of the Lenglongling fault and the eastern segment of the Tolaishan fault. The maximum displacements in the ascending and descending orbits in the LOS direction are 59.7 and 94.7 cm, respectively. The co-seismic slip results show that the strike, dip and average slip angles of the seismogenic fault are 108°, 79° dipping to SW, and 4°, respectively. On the whole, the fault is mainly of left-lateral, with a small amount of thrust component and only one co-seismic rupture center in our inversion result. The rupture center is located at a depth of ∼5 km below the surface, and the maximum slip is 3.1 m. The total seismic moment released by this earthquake is 1.28 × 1019 N·m, and the corresponding moment magnitude is 6.67. Finally, the static Coulomb stress change results show that parts of the Lenglongling fault, the Tolaishan fault, the Sunan-Qilian fault and the Minyue-Damaging fault are loaded, emphasizing the importance for earthquake risk assessment of these fault.

Source mechanism of the 2020 Mw 6.3 Nima earthquake derived from Bayesian inversions with InSAR observations: Insight into E-W extensional activity in the central Tibet

Normal faults and conjugate strike-slip faults have been considered to play an important role in response to the extension deformation of central Tibet. On 22 July 2020, a Mw 6.3 earthquake struck the Nima county, central Tibet, in China, which provides a rare opportunity to get insights into how the normal faults in central Tibet accommodates the east-west extension caused by the Indian-Eurasian convergence. In this study, the Sentinel-1 images are collected to measure the coseismic deformation associated with this 2020 event and image its slip distribution. To mitigate the atmospheric phase effects, the generic atmospheric correction online service (GACOS) model is used to correct the coseismic inteferograms. The final coseismic deformation results show mainly negative displacement with a maximum value of ∼ 30 cm in the line of sight (LOS) direction. After that, a Bayesian inversion method is used to invert the fault model. Our results reveal the optimal seismogenic fault of this event with a strike angle of 31.3°, a dip angle of 51.6°, and show that its slip distribution is dominated by normal slip with a maximum value of 2.55 m at a depth of 4.79–9.53 km, which suggest it’s a blind normal rupture with high east-trending dip angle. The total released geodetic moment is, equivalent to Mw 6.3. In addition, we analyze the Coulomb stress change due to the 2008 Gaize and this 2020 Nima events, suggesting the 2020 event should not be triggered by the 2008 event. Finally, we estimate an interseismic slip rate of 4.7±1.2 mm/yr on the Yibug Caka-RigainPun Co (YCRC) fault with published global navigation satellite system (GNSS) measurements. Given that these high frequent normal slip events but a low crustal extension rate of 4.7±1.2 mm/yr in this region, we speculate that the asthenosphere material upwelling should be also a possible reason for E-W extensional activities in central Tibet.

High Fall Risk Associated With Memory Deficit and Brain Lobes Atrophy Among Elderly With Amnestic Mild Cognitive Impairment and Mild Alzheimer's Disease.

ObjectivesThis study aimed to primarily examine the association between memory deficit and increased fall risk, second, explore the underlying neuroanatomical linkage of this association in the elderly with aMCI and mild AD.MethodsIn this cross-sectional study, a total of 103 older adults were included (55 cognitively normal, CN; 48 cognitive impairment, CI, elderly with aMCI, and mild AD). Memory was assessed by the Auditory Verbal Learning Test (AVLT). Fall risk was evaluated by the Timed Up and Go (TUG) Test, heel strike angles, and stride speed, which were collected by an inertial-sensor-based wearable instrument (the JiBuEn™ gait analysis system). Brain volumes were full-automatic segmented and quantified using AccuBrain® v1.2 from three-dimensional T1-weighted (3D T1W) MR images. Multivariable regression analysis was used to examine the extent of the association between memory deficit and fall risk, the association of brain volumes with memory, and fall risk. Age, sex, education, BMI, and HAMD scores were adjusted. Sensitivity analysis was conducted.ResultsCompared to CN, participants with aMCI and mild AD had poorer cognitive performance (p < 0.001), longer TUG time (p = 0.018), and smaller hippocampus and medial temporal volumes (p = 0.037 and 0.029). In the CI group, compared to good short delayed memory (SDM) performance (AVLT > 5), the elderly with bad SDM performance (AVLT ≤ 3) had longer TUG time, smaller heel strike angles, and slower stride speed. Multivariable regression analysis showed that elderly with poor memory had higher fall risk than relative good memory performance among cognitive impairment elderly. The TUG time increased by 2.1 s, 95% CI, 0.54∼3.67; left heel strike angle reduced by 3.22°, 95% CI, −6.05 to −0.39; and stride speed reduced by 0.09 m/s, 95% CI, −0.19 to −0.00 for the poor memory elderly among the CI group, but not found the association in CN group. In addition, serious medial temporal atrophy (MTA), small volumes of the frontal lobe and occipital lobe were associated with long TUG time and small heel strike angles; small volumes of the temporal lobe, frontal lobe, and parietal lobe were associated with slow stride speed.ConclusionOur findings suggested that memory deficit was associated with increased fall risk in the elderly with aMCI and mild AD. The association might be mediated by the atrophy of medial temporal, frontal, and parietal lobes. Additionally, increased fall risk, tested by TUG time, heel stride angles, and stride speed, might be objective and convenient kinematics markers for dynamic monitoring of both memory function and fall risk.

Turbine blade strike tests for evaluation and optimization of fish-friendly turbine

Widening the knowledge for fish injury and mortality mechanism caused by pressure, shear stress and blade strikes inside turbine was constructive for optimizing fish-friendly turbine design and turbine operation regime. A special designed test equipment was applied for simulating the rotating blade inside turbine passage, anesthetized fish (crucian carp) was placed on the route of the blade for strike tests. The fish length, blade thickness, strike angle, and strike speed were independent variables during the tests, the injury rate, degree of injury and mortality rate were analysed according to observation or anatomical examination after repeated tests. The injury types were classified into: imbalance, ribs broken, gill cover broken, internal hemorrhage and death. The injury severity was directly affected by strike speed under same blade thickness and fish length. The ratio of blade thickness and fish length also affect the injury rate. Multiple injuries can be observed on one fish after tests, and combined injuries are more likely to lead to death. In the fish-friendly turbine design, blade thickness in the leading edge and blade numbers shall be carefully considered and the rotational speed shall be calculated.

Simple foot strike angle calculation from three-dimensional kinematics: A methodological comparison

ABSTRACT A simple and accurate method of determining foot strike angle (FSA) during running can simplify data collections and validations of wearable sensors. The purpose of this study was to determine the validity of two simplified methods for estimating FSA and foot angle (throughout the ground contact) from three-dimensional kinematics. Markers were placed on the heel and head of the second metatarsal (HEEL-TOE) or on the lateral side of the head of the fifth metatarsal (HEEL-MET5). When compared to the reference foot segment, the HEEL-TOE method performed similarly with a minimal mean difference (0.28° [0.19°,0.36°], p < 0.001), a high Pearson’s r (r = 0.994; p < 0.001), and low bias (−0.20°±1.05°). Alternatively, the HEEL-MET5 method underestimated FSA: mean difference = 4.28° [4.07°,4.91°] (p < 0.001), Pearson’s r = 0.968 (p < 0.001), and bias = −4.58°±2.61°. Throughout the contact phase, significant SPM cluster regions were identified, indicating that the HEEL-MET5 method underestimated the angle of the foot for all foot strike patterns in the first 23–34% of the stance (p < 0.025). This study supports the idea that the HEEL-TOE method can be used as a simplified method for determining FSA from 3D kinematics. Researchers should proceed with caution when employing the HEEL-MET5 method, as it is likely underestimating FSA due to foot inversion in the early stance phase.

A Monte-Carlo based 3-D ballistics model for guiding bat carcass surveys using environmental and turbine operational data

Wind turbines cause direct mortality of bats through collision with turbine blades. However, accurate bat fatality estimates are unavailable for many facilities and regions due to lack of physically consistent guidance for surveying bat carcasses. We develop a Monte-Carlo based 3-D ballistics model to address this important gap to guide carcass surveys, help improve fatality estimates by combining it with statistical models and offer post-construction impact assessment guidelines. Monte-Carlo simulations account for variability of environmentally relevant parameters and subsequently the variability of the generated carcass fall zone distributions. The input parameters are bat characteristics, including mass, size, and drag coefficient, wind speed, turbine RPM, yaw, bat flight speed, bat strike angle, and bat strike locations on the rotor. Using turbine SCADA (Supervisory Control and Data Acquisition), bat biometrics data, and carcass drag coefficient range, probability density functions of the input parameters were computed. With the help of carcass survey and SCADA details, bat fatalities were selected, and Monte-Carlo based ballistics model simulations were performed using corresponding values of the input parameters of the ballistics model. The surveyed carcass location for a bat found on the same day was in good agreement with the modelled fall zone distribution, providing a measure of model validation. Next, simulations were conducted for a bat fatality for which the carcass was found four days after collision. It was found that the observed location was within the modeled fall zone distribution showing the model capacity for planning surveys. Further, Monte-Carlo based 3-D ballistics model simulations were performed for the full migration season and the resulting 1-D (radial) and 2-D (surface) histograms were compared with the survey 1-D and 2-D histograms, respectively. The modelled 2-D fall zone distribution hot spot overlaps with surveyed carcass positions indicating the model robustness over a wide range of meteorological conditions and time scales. However, by comparison, the modeled 1-D fall zone distribution was found to be different from the surveyed 1-D fall zone distribution. We hypothesize that uncertainty in bat radial strike location (distribution of bat collisions on turbine blades in radial direction) distribution is primary source of difference between the surveyed and modelled 1-D fall zone distribution. There are no measurements available for this key input parameter. As a next step, the sensitivity of carcass fall zone distributions with respect to bat radial strike location distributions were tested. It was found that the probability density function for bat radial strike location affects the modelled fall zone distributions significantly. There is a need to measure bat radial and angular strike locations which can be used as input in the ballistics modeling framework to improve prediction of carcass fall zone distributions. The proposed model is useful for carcass survey planning, improving survey estimates, designing turbine curtailment studies, and collision risk modeling.

Gravity aspects from recent gravity field model GRGM1200A of the Moon and analysis of magnetic data

The gravity aspects for the Moon (the gravity disturbance, the Marussi tensor, two gravity invariants, dimensionality ratio, the strike angles, and the virtual deformations), all combined with magnetic anomalies and detailed surface topography, allow new views of specific locations on the Moon. Using these new gravity quantities, we hypothesize the following for several features on the Moon. A dike-like intrusion (exceeding ~100 km in length) from inside to outside of the Clavius crater likely solidified at the time of the existence of lunar dynamo. Mare Crisium analyses show a specific distribution of faulting across the mare. The same size impacts, Crisium and Clavius, present the dilatational deformation that is smoother for Crisium, while Clavius is under variable concentric compression due to an uplift of denser rock. Mare Orientale deformation not only confirmed the prior finding of the near surface faults, but also reveals a nature of the faulting (expansion vs compression blocks). Magnetic analyses of related lunar anomalies constrain mascon extent under the Copernicus structure and outline contraction areas from cooling of the upwelled mantle material. Mare Imbrium impact event has demagnetized regolith along with the Copernicus crater using a novel mechanism of shock propagation while plasma demagnetization. Clavius' magnetic field reveals magnetization that is likely more than four billion years old. Mare Crisium impact has a unique magnetization signature by impact related transient field. Mare Orientale showed, for the first-time, rippling-like effect of the Moon's mantle. This process of upwelled rippled mantle allows efficient demagnetization of the Orientale basin. For the first time, the application of the gravity aspects has been extended from the Earth to the Moon. This approach opens a new and inspiring field of planetary studies and point to otherwise hardly detectable phenomena. More detailed studies should follow.

Analytical Investigation of Ricochet Range of Ogive—Shaped Nose Projectile Obliquely Penetrating Thick Steel Target

The ricochet phenomenon has been studied worldwide for a long time in consideration of its significance in ballistics. A ricochet projectile has proven to be worthless to its launcher, as warheads fail to penetrate the interior of targets and strike the facilities and personnel of enemies effectively. A large portion of related research has been dedicated to avoiding ricocheting, which mainly focuses on improving the penetration ability of a projectile in order to obtain a better penetration effect, while investigations on the proactive protection of key targets from damage caused by a ricochet projectile are minor. This study analytically explores the ricochet range of a projectile obliquely penetrating a thick steel target. Firstly, the moment of momentum equation of the ricochet projectile based on theoretical mechanics is utilised to analytically calculate its trajectory, where a mathematical model of a two-stage ricochet impacting is established through the geometrical analysis of the ricochet process for determining the ricochet range of a projectile and the size of the bulletproof structure. Then, impact experiments of a projectile obliquely penetrating thick steel targets at different striking velocities and inclination angles are carried out, and the influences of the striking velocity and angle of attack on the damage pattern, area and penetration depth are discussed to identify the ricochet phenomenon. Moreover, the deflection angle of the ricochet projectile is computed, which is compared with the experimental measurements in order to validate the accuracy of this proposed model. This proposed research may promote security protection during live-firing training and provide a theoretical foundation for the optimisation of purposeful protection.

The hydraulic fracturing with multiple influencing factors in carbonate fracture-cavity reservoirs

In carbonate fracture-cavity reservoirs, such as the Tahe oilfield in China, natural cavities are the main storage space of oil. It is critical to control the propagation of hydraulic fractures in order to enhance the connectivity between wellbores and oil-filled cavities. In this work, the influencing factors, including natural fracture strike angle, confining stress, the internal fluid pressure of natural cavities and fluid injection pressure are investigated numerically using the TOUGH-AiFrac simulator. Our results show that when multiple influencing factors are taken into account, natural fractures have dominant impacts on hydraulic fractures propagation, followed by the impacts of confining stress. These two influencing factors are critical to the hydraulic fracturing design in carbonate fracture-cavity reservoirs. Fluid injection pressure control can be limited by the capacity of the field equipment and the influence of cavity internal fluid pressure that tends to attract propagating fractures depending on the site-specific reservoir conditions. The present work provides guidance on how to optimize the design of hydraulic fracturing in carbonate fracture-cavity reservoirs.

Sensitivity Analysis of Fault Failure Parameters to the Maximum Tsunami Heights

The initial waveform of the tsunami is determined by fault parameters such as the width and the length of the fault, the strike angle, the dip angle, the slip angle, the vertical distance from the seabed to the fault, and the displacement. Consequently, the tsunami run-up height is changed for various characteristics of the incoming tsunami waves. In this study, we present the analysis of the effect of fault parameters on the maximum tsunami height. The maximum tsunami height was calculated by altering the fault parameter in the tsunami numerical model and the parameter sensitivity to the maximum tsunami height was demonstrated. The depth of the fault did not significantly affect the maximum tsunami height, but the angle and the displacement are related to the maximum tsunami height. Furthermore, the strike angle and the slip angle have significant effects on the maximum tsunami height.

The Relationship of Some Kinematic Variables to the Performance of Forehand Clear Stroke with Accuracy in Badminton Players

The study aimed to: Recognizing the values of a number of kinematical variables for the performance of the forehand clear stroke for badminton players. Recognizing the values of the accuracy test for the performance for the forehand clear stroke of badminton players. Recognizing the relationship between a number of kinematical variables and the accuracy values of the forehand clear stroke for badminton players. In order to verify the objectives of the study, the researcher had assumed the following: - There is a significant relationship between the values of a number of bio kinematical variables and the accuracy values of the forehand clear stroke for badminton players. The researchers used the descriptive approach with the correlational style, for its suitability to the study nature, The research sample was selected from the players of the elite clubs registered with the Iraqi Badminton Federation, and the research sample consisted of (7) players. The researcher used the resources, scientific references, interviews, questionnaires, testing, measurement and scientific observation as means of data collecting, the study included biokinematical variables, and the accuracy of the forehand clear stroke skill. The main experiment was conducted in two different locations due to the presence of the research sample (4) of them representing the Iraqi national badminton team in Baghdad and (3) players representing the Akad Sports Club in Erbil province, and in order to achieve the first scientific and technical observation, two digital cameras were used. At a speed (240 f /s), the first camera was placed on the side of the player's hitting arm at a distance of (4 m) and with a lens height (1.25 m) , and the second was placed in front of the player at a distance of (3.35 m) With a lens height (1.25 m). In order to achieve the second scientific and technical observation, two digital cameras were used. The first camera was placed on the side of the player's hitting arm at a distance (5.35 m) and a lens height (1.29 m), it was set at speed (300f /s), and the second camera was placed in front of the player at a distance (3.70 m) and with a lens height (1.29 m), and it was set at speed (210 f/s). The data were statistically handled using the (SPSS) program to obtain (the arithmetic mean, standard deviation, coefficient of variation, simple correlation coefficient, and T-test for independent samples. The researchers concluded: - The variables (horizontal displacement, horizontal velocity and velocity resultant) for BMC in the final phase of the forehand clear stroke skill had a positive significant relationship with accuracy. - The shuttlecock starting velocity in the forehand clear stroke skill had a direct relationship with accuracy. - Accuracy has a direct relationship with variable of the striking arm wrist joint angle and inversely with the forearm angle with the racket variable at the moment of maximum return of the racket in the forehand clear stroke skill. - The relationship was direct between (shoulder angle, forearm angle with the racket) variables (each separately) with the accuracy at the moment of shuttlecock impact in the forehand clear stroke skill. - The increase in the angular deference of the forearm with racket was significantly correlated with accuracy in the main phase of the forehand clear stroke skill. - There is a direct relationship between the angular velocity of the forearm with the racket variable with the accuracy in the main phase of the forehand clear stroke skill. Through the conclusions, the researchers recommend: - The necessity to direct the players to pay attention to the ideal angles of technical performance of badminton skills. - Directing the coaches to use a kinematic analysis programs or seeking the help of an expert and specialist in kinetic analysis to correct some of the players' performance errors that are not seen with the naked eye. - Paying attention to the results of the current study for use by workers in the field of badminton training and education.

Reexamination of tsunami source models for the twentieth century earthquakes off Hokkaido and Tohoku along the eastern margin of the Sea of Japan

Large earthquakes around Japan occur not only in the Pacific Ocean but also in the Sea of Japan, and cause both damage from the earthquake itself and from the ensuing tsunami to the coastal areas. Recently, offshore active fault surveys were conducted in the Sea of Japan by the Integrated Research Project on Seismic and Tsunami Hazards around the Sea of Japan (JSPJ), and their fault models (length, width, strike, dip, and slip angles) have been obtained. We examined the causative faults of M7 or larger earthquakes in the Sea of Japan during the twentieth century, comprising events of 1940, 1964, 1983, and 1993, using seismic and tsunami data. The 1940 off Shakotan Peninsula earthquake (MJMA 7.5) appears to have been caused by the offshore active faults MS01, MS02, ST01, and ST02 as modeled by the JSPJ. The 1993 off the southwest coast of Hokkaido earthquake (MJMA 7.8) likely occurred on the offshore active faults OK03a, OK03b, and OK05, while the 1983 Central Sea of Japan earthquake (MJMA 7.7) probably related to MMS01, MMS04, and MGM01. For these earthquakes, the observed tsunami waveforms were basically reproduced by tsunami numerical simulation from the offshore active faults with the slip amounts obtained by the scaling relation with three stages between seismic moment and source area for inland earthquakes. However, the observed tsunami runup heights along the coast were not reproduced at certain locations, possibly because of the coarse bathymetry data used for the simulation. The 1983 west off Aomori (MJMA 7.1) and the 1964 off Oga Peninsula (MJMA 6.9) earthquakes showed multiple faults near the source area that could be used to reproduce the observed tsunami waveforms; therefore, we could not identify the causative faults. Further analysis using near-field seismic waveforms is required for their identification of their causative faults and their parameters. The scaling relation for inland earthquakes can be used to obtain the slip amounts for offshore active faults in the Sea of Japan and to estimate the coastal tsunami heights and inundation area which can be useful for disaster prevention and mitigation of future earthquakes and tsunamis.Graphical

Three-dimensional magnetotelluric inversion considering electrical anisotropy with synthetic and real data

Electrical anisotropy increases the non-uniqueness of magnetotelluric (MT) inversions. However, it is still useful to develop MT anisotropic inversion to provide new knowledge for this field. In this study, we developed a three-dimensional (3-D) MT inversion code considering electrical anisotropy. The forward procedure is based on a staggered-grid finite-difference method and solves the governing equation for the electric fields with a direct method. The values of a traditional objective function and its gradient could then be calculated. The inversion procedure was completed with a well-developed subroutine of non-linear conjugate gradient method. Synthetic tests for different isotropic models indicate the validity of this inversion code. Furthermore, we performed 3-D anisotropic inversions for synthetic and real data. The results indicate that vertical resistivity is still indistinguishable in the anisotropic inversion results. In our synthetic tests, it becomes more difficult to recover low-resistivity components of anisotropic anomalies as the depth increases, and the vertical sizes of anisotropic anomalies are reduced, as characterized by a much shallower bottom boundary. The anisotropic strike angle is not as stable as the principal resistivities in the inversion process. Under the same changes in model parameters, the strike angle may cause larger deviations of the responses than the principal horizontal resistivities. With this code, we revisited the field data collected at the northern margin of the Tibetan Plateau. The inversion results indicate a possible anisotropic anomaly exists below the boundary between the plateau and its northern neighbor. This anisotropic anomaly could represent an area of concentration of shear deformation.