Velocity Variation of Opak Fault GNSS Observation Station 2006 Yogyakarta Post-Earthquake

SUMMARY We use the recently deployed ScanArray network of broad-band stations covering most of Norway and Sweden as well as parts of Finland to analyse the propagation of Rayleigh waves in Scandinavia. Applying an array beamforming technique to teleseismic records from ScanArray and permanent stations in the study region, in total 159 stations with a typical station distance of about 70 km, we obtain phase velocities for three subregions, which collectively cover most of Scandinavia (excluding southern Norway). The average phase dispersion curves are similar for all three subregions. They resemble the dispersion previously observed for the South Baltic craton and are about 1 per cent slower than the North Baltic shield phase velocities for periods between 40 and 80 s. However, a remarkable sin(1θ) phase velocity variation with azimuth is observed for periods >35 s with a 5 per cent deviation between the maximum and minimum velocities, more than the overall lateral variation in average velocity. Such a variation, which is incompatible with seismic anisotropy, occurs in northern Scandinavia and southern Norway/Sweden but not in the central study area. The maximum and minimum velocities were measured for backazimuths of 120° and 300°, respectively. These directions are perpendicular to a step in the lithosphere–asthenosphere boundary (LAB) inferred by previous studies in southern Norway/Sweden, suggesting a relation to large lithospheric heterogeneity. In order to test this hypothesis, we carried out 2-D full-waveform modeling of Rayleigh wave propagation in synthetic models which incorporate a steep gradient in the LAB in combination with a pronounced reduction in the shear velocity below the LAB. This setup reproduces the observations qualitatively, and results in higher phase velocities for propagation in the direction of shallowing LAB, and lower ones for propagation in the direction of deepening LAB, probably due to the interference of forward scattered and reflected surface wave energy with the fundamental mode. Therefore, the reduction in lithospheric thickness towards southern Norway in the south, and towards the Atlantic ocean in the north provide a plausible explanation for the observed azimuthal variations.

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Analytical predictor–corrector entry guidance for hypersonic gliding vehicles

International Journal of Nonlinear Sciences and Numerical Simulation ◽

10.1515/ijnsns-2019-0290 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Huatao Chen ◽

Kun Zhao ◽

Juan L.G. Guirao ◽

Dengqing Cao

Keyword(s):

Feedback Control ◽

Velocity Variation ◽

Analytical Relation ◽

Aerodynamic Load ◽

Quasi Equilibrium ◽

Bank Angle ◽

Entry Guidance ◽

Guidance Algorithm ◽

Predictor Corrector ◽

Guidance Problem

AbstractFor the entry guidance problem of hypersonic gliding vehicles (HGVs), an analytical predictor–corrector guidance method based on feedback control of bank angle is proposed. First, the relative functions between the velocity, bank angle and range-to-go are deduced, and then, the analytical relation is introduced into the predictor–corrector algorithm, which is used to replace the traditional method to predict the range-to-go via numerical integration. To eliminate the phugoid trajectory oscillation, a method for adding the aerodynamic load feedback into the control loop of the bank angle is proposed. According to the quasi-equilibrium gliding condition, the function of the quasi-equilibrium glide load along with the velocity variation is derived. For each guidance period, the deviation between the real-time load and the quasi-equilibrium gliding load is revised to obtain a smooth reentry trajectory. The simulation results indicate that the guidance algorithm can adapt to the mission requirements of different downranges, and it also has the ability to guide the vehicle to carry out a large range of lateral maneuvers. The feedback control law of the bank angle effectively eliminates the phugoid trajectory oscillation and guides the vehicle to complete a smooth reentry flight. The Monte Carlo test indicated that the guidance precision and robustness are good.

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Accurate Simulation of the Four Modes of Post-Die Extrudate Shape Distortion

International Polymer Processing ◽

10.1515/ipp-2020-3995 ◽

2021 ◽

Vol 36 (1) ◽

pp. 69-78

Author(s):

M. Gupta

Keyword(s):

Layer Structure ◽

Die Design ◽

Velocity Variation ◽

Shape Distortion ◽

Exit Velocity ◽

Extrusion Die ◽

Combined Flow ◽

Extruded Product ◽

Simulation Results ◽

Extrudate Distortion

Abstract A combined flow, thermal and structural analysis is employed to simulate post-die extrudate distortion in different profile dies. All four factors which can cause extrudate distortion, namely, nonuniform exit velocity distribution, extrudate shrinkage, extrudate draw down, and deformed shape of the calibrator or sizer profile, are simulated. To analyze the effect of exit velocity variation on extrudate distortion, the parameterized geometry of a simple profile die is optimized using an extrusion die optimization software. The simulation results presented for a bi-layer profile die successfully demonstrate how gradually changing profile shape in successive calibrators/sizers can be used to simplify the die design for extrusion of complex profiles. The predicted extrudate shape and layer structure for the bi-layer die are found to accurately match with those in the extruded product.

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An Ultrahigh-Sensitivity Graphene Resonant Gyroscope

Nanomaterials ◽

10.3390/nano11081890 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1890

Author(s):

Yang Lu ◽

Zhan-She Guo ◽

Shang-Chun Fan

Keyword(s):

Angular Velocity ◽

High Sensitivity ◽

Velocity Variation ◽

Beam Length ◽

Sensing Element ◽

Finite Element Software ◽

Resonant Beam ◽

Frequency Output ◽

Length Width ◽

Ultrahigh Sensitivity

In this study, a graphene beam was selected as a sensing element and used to form a graphene resonant gyroscope structure with direct frequency output and ultrahigh sensitivity. The structure of the graphene resonator gyroscope was simulated using the ANSYS finite element software, and the influence of the length, width, and thickness of the graphene resonant beam on the angular velocity sensitivity was studied. The simulation results show that the resonant frequency of the graphene resonant beam decreased with increasing the beam length and thickness, while the width had a negligible effect. The fundamental frequency of the designed graphene resonator gyroscope was more than 20 MHz, and the sensitivity of the angular velocity was able to reach 22,990 Hz/°/h. This work is of great significance for applications in environments that require high sensitivity to extremely weak angular velocity variation.

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Monitoring Master Swimmers’ Performance and Active Drag Evolution along a Training Mesocycle

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18073569 ◽

2021 ◽

Vol 18 (7) ◽

pp. 3569

Author(s):

Henrique P. Neiva ◽

Ricardo J. Fernandes ◽

Ricardo Cardoso ◽

Daniel A. Marinho ◽

J. Arturo Abraldes

Keyword(s):

Aerobic Training ◽

Training Period ◽

Velocity Variation ◽

Hydrodynamic Drag ◽

Swimming Training ◽

Front Crawl ◽

Maximal Intensity ◽

Before And After ◽

Active Drag

This study aimed to analyze the effects of a swimming training mesocycle in master swimmers’ performance and active drag. Twenty-two 39.87 ± 6.10 year-old master swimmers performed a 25 m front crawl at maximal intensity before and after a typical four-week training mesocycle. Maximum, mean and minimum speeds, speed decrease and hip horizontal intra-cyclic velocity variation were assessed using an electromechanical speedometer, and the active drag and power to overcome drag were determined using the measuring active drag system. Maximum, mean and minimum front crawl speeds improved from pre- to post-training (mean ± 95% CI: 3.1 ± 2.8%, p = 0.04; 2.9 ± 1.6%, p = 0.01; and 4.6 ± 3.1%, p = 0.01; respectively) and the speed decrease along the 25 m test lowered after the training period (82.5 ± 76.3%, p = 0.01). The training mesocycle caused a reduction in the active drag at speeds corresponding to 70% (5.0 ± 3.9%), 80% (5.6 ± 4.0%), and 90% (5.9 ± 4.0%), but not at 100% (5.9 ± 6.7%), of the swimmers’ maximal exertions in the 25 m test. These results showed that four weeks of predominantly aerobic training could improve master swimmers’ performance and reduce their hydrodynamic drag while swimming mainly at submaximal speeds.

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