Velocity Cone Research Articles

Correlation between Shear-Wave Velocity and Dynamic Cone Resistance for Gravelly Soil

Correlation between Shear-Wave Velocity and Dynamic Cone Resistance for Gravelly Soil

Reciprocal Safety Velocity Cones for Decentralized Collision Avoidance in Multi-Agent Systems

In this paper, we solve the inter-agent collision avoidance problem in an arbitrary n-dimensional Euclidean space using reciprocal safety velocity cones (RSVCs). We propose a decentralized feedback control strategy that guarantees simultaneously asymptotic stabilization to a reference and collision avoidance. Our algorithm is purely decentralized in the sense that each agent uses only local information about its neighbouring agents. Moreover, the proposed solution can be implemented using only inter-agent bearing measurements. Therefore, the algorithm is a sensor-based control strategy which is practically implementable using a wide range of sensors such as vision systems and range scanners. Simulation results in a two dimensional environment cluttered with agents shows that the number of possible deadlocks is marginal and decrease with the decrease in the clutteredness of the workspace.

On Free Velocity Cones of Narrow Passages of High-DoF Kinematic Chains

Narrow passages in free space pose great challenges to many sampling-based motion planners. In problems with high-dimensional configuration spaces (C-spaces), narrow passages in free space (C-free) can be hard to find and navigate and, sometimes, even counterintuitive. In this article, we present an algorithm to construct cones of available instantaneous velocities (“free velocity cones” or, briefly, “free cones”) on the boundary of C-free to facilitate finding and navigating narrow passages. This is accomplished by first developing free cones and associated measures of local C-space narrowness for a single rigid link. These results are then extended to kinematic chains (open and closed) of arbitrary degrees of freedom. It turns out that the degeneracy of the free cones dictates the existence of C-space narrow passages, and the locations and orientations of the links in the workspace relate intimately to the corresponding connected component of C-free. This observation leads us to a modified probabilistic roadmap (M-PRM) algorithm and a modified rapidly exploring random vine (M-RRV) algorithm of combining the enumeration of topological components and random sampling of the free cones. Experimental results from applying our algorithms to several challenging examples show that our new algorithms are more efficient than some variants of the PRM algorithms, and several variants of the rapidly exploring random tree (RRT) algorithms, such as RRT-CONNECT and RRV.

Efficient Trajectory Optimization for Constrained Spacecraft Attitude Maneuvers

This paper introduces an optimal trajectory planner for spacecraft rest-to-rest attitude transfers subject to input saturation, angular velocity, and nonconvex exclusion cone constraints. The proposed solution adapts the Projection-Operator-Based Newton’s Method for Trajectory Optimization (PRONTO) to address the nonlinearity of the unit quaternion manifold. The system constraints are then handled using a modified interior point method designed to remain applicable when an intermediate solution estimate is infeasible. Through an extensive numerical study, the proposed solution is compared with a state-of-the-art commercial solver, its computational efficiency is demonstrated, and its unique ability to provide feasible intermediate solutions is highlighted. These results strongly indicate PRONTO as a suitable real-time optimal maneuver planner for spacecraft attitude control.

Rigorous test of the performance of shear-wave velocity correlations derived from CPT soundings: A case study for Groningen, the Netherlands

An improved correlation between shear-wave velocity VS and cone penetration test (CPT) parameters was derived for the Groningen region, the Netherlands, using a set of 154 pairs of CPTs and seismic CPTs. An analysis of a high-quality subset showed that the subdivision into Holocene versus Pleistocene intervals or into cohesive versus non-cohesive intervals did not significantly improve correlation, nor did filtering out of the transition intervals between clay and sand in the non-cohesive dataset. In addition, using qt or qc resulted in similar regression results. We therefore propose a single new equation and we applied this to all available CPTs in the region. The analysis of the fitting bias showed that there is a trend relative to the measured VS. We therefore recommend performing SCPT measurements when very soft soils (VS < ~100 m/s) are encountered, rather than relying on the empirical correlation based on CPT parameters.The comparison of the VS30 values from CPTs to the model VS30 of Groningen shows that correlation is excellent: 90% of the calculated VS30 values from the CPTs fall within one standard deviation of the VS30 of the corresponding geological zone of the model. Although the resulting CPT-VS correlation is specific for the Groningen region, the approach can be applied to other regions with a paired SCPT-CPT dataset.

Effect of Viscosities on the Spray Characteristics of Pressure Swirl Nozzle

The effects of medium viscosity on the spray flow rate, spray Sauter Mean Diameter, droplet velocity and spray cone angle of pressure swirl nozzles are investigated by making use of the particle dynamics analysis system and high-speed photographic system. Based on the axial and radial distribution characteristics of Sauter Mean Diameter and droplet velocity, the water-glycerol mixture is used to simulate medium with a wide range of viscosities. It is found that with the increase of viscosity, the turbulence of the medium flow and the swirling effect is weakened, and the rated pressure becomes larger and the spray flow rate increases. Spray Sauter Mean Diameter and droplet axial velocity becomes larger, while the spray cone angle decreases. The development of the axial velocity distribution of spray cone is characterized by the radial and axial position parameters. The area of the large-droplet region on both sides of spray cone becomes larger, and the area of small-droplet region near the axis becomes smaller.

Scattering of neutrons on $${\upalpha }$$-particles in three-dimensional space

This letter demonstrates that there are some mistakes in the article of Roshan et al (Pramana – J. Phys. 90(3): 30, 2018) in dealing with the scattering of neutrons on $${\upalpha }$$ -particles in three-dimensional space. In fact, there is no one-to-one correspondence between the incident neutron energy and the scattering angle of the $${\upalpha }$$ -particle even if they have definite velocities before scattering. Instead, the situation is complex, and all the scattered $${\upalpha }$$ -particles will emit in a cone, which is called the velocity cone. At each scattering angle, which is smaller than the apex angle of the velocity cone, there are two groups of $${\upalpha }$$ -particles with different kinetic energies.

Evaluation of failure modes and undrained shear strength by cone penetrometer for Natural Gas hydrate-bearing pressure-core sediment samples recovered from the Krishna–Godavari Basin, offshore India

Compressional wave velocity measurements and cone penetration tests were carried out for pressure cores recovered from the Krishna–Godavari Basin off the eastern coast of India, using an instrumented pressure testing chamber constructed by the Japanese National Institute of Advanced Industrial Science and Technology. For pressure cores with high gas hydrate saturations (Sh) and exhibited high compressional wave velocities also display a high loading force that resulted in tensile failure. A pressure core sample with low compressional wave velocities and low gas hydrate saturations led to a low loading force, which resulted in radial shear. The cone factor connecting the cone resistance and the undrained shear strength, Nk, was estimated using cone penetration testing and the uniaxial compressional results. We estimated its value as Nk = 45 by using a uniaxial compression loading speed of 0.01%/min and a cone insertion loading speed of 0.25 mm/s. Undrained shear strengths, estimated from cone penetration results using Nk = 45, were assumed to be equal to the tensile strengths between hydrate-hydrate and hydrate-particle interface when Sh is less than 50% and increases when Sh is more than 50% assuming that gas hydrate morphology was matrix supporting.

Performance evaluation of newly developed variable rate sprayer for spray deposition in guava orchard

Application of pesticide inside orchards with conventional sprayers often results in an inefficient application as these are constant rate applicators and also the significant amount of pesticide gets lost in spaces between trees. To reduce the pesticide losses inside orchards, a variable rate sprayer was developed which sprayed only after the occurrence of the tree and according to the size of the tree. The performance of the developed variable rate sprayer was evaluated inside guava trees to quantify the spray deposition at six different plant positions. The sprayer was operated at three forward speeds (2, 3 and 4 km/h) with four air velocity levels (20, 25, 30 and 35 m/s) and two different types of nozzles (hollow cone and flat fan nozzle). The observed data was statistically analyzed to study the significance of selected parameters on spray deposition. The spray deposition was found to significantly increase with the increase in air velocity and hollow cone nozzle was able to deposit more amount of spray as compared to flat fan nozzle. There was no significant variation was observed with different forward speeds. The maximum spray was deposited on upper leaf surface at all selected plant position. The uniform spray deposition was observed with the air velocity of 35 m/s and hollow cone nozzle. Even though the developed variable rate sprayer varied the discharge of nozzles according to tree size, it was able to deposit the adequate amount of spray at all selected plant positions.

Hotspot volcanism in the southern South Atlantic: Geophysical constraints on the evolution of the southern Walvis Ridge and the Discovery Seamounts

The southern Atlantic hosts a variety of magmatic structures, namely the Walvis Ridge, the Discovery Seamounts and the Shona Ridge, which are believed to be related to the evolution/movement of hotspots. Although the basement of the Walvis Ridge has been sampled at different locations, geophysical data are too sparse to provide sufficient information about its deeper structure to compare it with other hotspot tracks. The Discovery Seamounts represent a completely different type feature in a way that it cannot be connected to any onshore volcanic feature. However, geological sampling of the volcanic basement indicates that the petrology of the Discovery track is very similar to Gough Island and the southern branch of Walvis Ridge. Both structures erupted into already existing seafloor and so have been seismically investigated to document how/if an associated thermal anomaly might have modified the underlying and surrounding oceanic crust. Seismic lines for both structures indicate rather normal seismic velocity distributions for oceanic crust. Both, the Walvis Ridge and the largest volcano of the Discovery Seamounts have a maximum thickness in our research area of ~13km. An interesting difference between these structures is a high velocity cone (>6km/s) at 2.4km depth in the central part of Discovery Seamount. This might indicate a primarily intrusional type of seamount such as has been reported for several similar structures. In contrast the Walvis Ridge velocity structure does not show evidences for a shallow intrusional cone, but seismic velocities typical for oceanic layer 3 at a more or less constant depth level along the entire profile. This might indicate that the ridge's present-day topography is built mainly by extrusive material.

Large-gap quantum spin Hall state in functionalized dumbbell stanene

Two-dimensional dumbbell (DB) stanene has been proposed as a promising candidate material for realizing quantum spin Hall effect (QSHE) by Tang et al. [Phys. Rev. B 90, 121408 (2014)]. However, the small bulk-gap limits its possible applications at room temperature. Based on first-principles calculations, we predict that its band gap can be enhanced to 148 meV under methyl-functionalization, which can be further tuned by applying lattice strain. The QSHE is confirmed by s-px,y band inversion, topological invariant Z2 = 1, and helical gapless edge within bulk band gap. Notably, the characteristic properties of edge states, such as the large Fermi velocity and Dirac cone, can be modulated by edge modification. The effects of substrates on topological properties are explored when it is grown on various substrates, like SiC, h-BN, and Bi2Te3 sheets. These findings provide significant guidance for future fabrication and realistic applications of QSHE based on stanene in spintronics.

KidVO: a kinodynamically consistent algorithm for online motion planning in dynamic environments

Purpose– The purpose of this paper is to propose an efficient method, called kinodynamic velocity obstacle (KidVO), for motion planning of omnimobile robots considering kinematic and dynamic constraints (KDCs).Design/methodology/approach– The suggested method improves generalized velocity obstacle (GVO) approach by a systematic selection of proper time horizon. Selection procedure of the time horizon is based on kinematical and dynamical restrictions of the robot. Toward this aim, an omnimobile robot with a general geometry is taken into account, and the admissible velocity and acceleration cones reflecting KDCs are derived, respectively. To prove the advantages of the suggested planning method, its performance is compared with GVOs, the so-called Hamilton-Jacobi-Bellman equation and the rapidly exploring random tree.Findings– The obtained results of the presented scenarios which contain both computer and real-world experiments for complicated crowded environments indicate the merits of the suggested methodology in terms of its near-optimal behavior, successful obstacle avoidance both in static and dynamic environments and reaching to the goal pose.Originality/value– This paper proposes a novel method for online motion planning of omnimobile robots in dynamic environments while considering the real capabilities of the robot.

Human motion control with physically plausible foot contact models

The foot-to-ground contact model plays an important role in the simulation of highly dynamic motions, such as turns and kicks. In this paper, we propose a method for solving dynamically cumbersome slipping contact problems, which are frequently observed in highly dynamic motions. We employ and modify a combination of two different types of cones representing the inequality constraints of a contact model: the friction cone and the velocity cone. The friction cone makes character animation physically plausible while the velocity cone allows a character to perform a sharp turn without foot-to-ground penetration. Our system effectively simulates human behavior using an inverted pendulum on a cart (IPC) model and motion capture data. In the pre-processing step, we analyze motion capture data to extract meaningful information for the IPC model. At run-time, our system produces a physically simulated character by tracking the desired motion that is predicted by the IPC model. We formulate human motion control as a quadratic programming satisfying the proposed foot-to-ground contact constraints. Our examples show that the proposed system can produce physically plausible character animation without noticeable foot-to-ground contact artifacts.

Validation of impact penetrometer data by cone penetration testing and shallow seismic data within the regional geology of the Southern North Sea

This study presents the assessment of total cone resistance from in situ deceleration measurements using the Lance Insertion Retardation meter (LIRmeter) in the Southern North Sea. The penetrometer is equipped with a measurement lance that is up to 6 m in length. The aim was to validate LIRmeter data interpretation within the regional geological context by comparison with static velocity cone penetration testing (CPT) and sub-bottom profiles. In total, 13 datasets were taken, in addition to preexisting hydroacoustical and static velocity CPT datasets. The dynamically acquired data were processed and compared to the reference static velocity data. The validation encourages the use of acceleration-based dynamic penetration tests, since a high degree of agreement was demonstrated between independently acquired dynamic and static cone resistance data. Moreover, the results reveal evidence of two successive formations with different geotechnical properties, consistent with existing knowledge on the regional setting. Additionally, there is novel indication of an incised glacial valley with muddy low-permeability sediments extending much further than reported to date, which would necessitate updating of older maps. The main advantage of penetrometer-based deceleration measurements lies in the robustness of the method, and the reliability of the sensors. However, penetration depth is, for dimensioning reasons, limited to the order of a few meters. Additionally, data processing includes the dependency of knowledge about the soil type to correct the dynamic data. These limitations can be satisfactorily outweighed by combination with reference data from static velocity tests, as demonstrated by integrating these data into a soil classification scheme.

INTRODUCTION TO NUMERICAL ANALYSIS OF DIRECTED FRAGMENTATION WARHEADS

The aim of the paper is to presents one of the possible approaches to the numerical analysis of the behaviour of directed fragmentation war heads. These kinds of warheads consists of: metallic or composite cover, explosive material and a driven and fragmentation liner. The explosives are initiated by a booster causes driving the liner in a few milliseconds up to about 900 m/s. The liner fragments into many parts during this intensive and dynamic load. The fragments move in a cone which dimensions depend on the warheads shape and mechanical parameters of others warheads parts. All of the warheads elements are selected to meet the assumed parameters. The fragments velocity, their mass or geometric dimensions and cone angle are the most important parameters of the warheads fragments. Such a warhead, in the initial phase of the liner driving can be numerically modelled in the field of the continuum damage mechanics. Such a description is presented in other papers. This approach in a further phase of driving cause the increases of inaccuracies. Therefore, this paper proposes the use of ALE and FSI approach to describe the behaviour of the fragmentation warheads. A three-dimensional numerical model of the directed fragmentation warheads was made in the MSC Patran, and the dynamic phenomena analysis used a nonlinear finite element method implemented in the LS-Dyna program.

Evaluating the effectiveness of rolling impact compaction at a brownfield site with high and low frequency seismic surface waves and geotechnical testing

ABSTRACTUsing a case study from a brownfield site in Australia that contained substantial uncontrolled crushed rock fill, we demonstrate that innovative geophysics and ground improvement using rolling dynamic compaction can provide alternatives to costly excavation, removal and re‐engineering of soils. This approach can also overcome some of the limitations of conventional geotechnical testing in such conditions. The process we have developed involves selection and levelling of trial areas within larger brownfield sites. These are initially screened with electromagnetic geophysics to target environmental sampling sites, buried objects and local areas of potentially unsuitable or contaminated soils for removal and replacement. High and low frequency surface wave testing is then completed along closely spaced lines within the trial areas using specially adapted Multi‐channel Analysis of Surface Waves (MASW) methods and a modified land streamer. This provides S‐wave velocity distributions within fill and deeper materials over two depth ranges, at high vertical resolution from approximately 0 to 2 m and at lower resolution from 2 to ~10 m. These results are compared with geotechnical engineering test information. Ground improvement works are then undertaken using rolling dynamic compaction with a ‘square’ impact roller.Within this brownfield trial area, geotechnical testing showed that post‐compaction in‐situ densities increased by about 6 to 10%, while S‐wave velocities increased by up to 40%. This clearly demonstrates the sensitivity of S‐wave velocities to soil and fill modulus. The S‐wave velocity sections also showed the consistency of the landform created by impact rolling and that both high and low frequency MASW testing is needed for more accurate assessment of the densification of both shallow and deeper fill. Normalized S‐wave velocity difference sections and Cone Penetrometer Testing (CPT) provided a clear indication of the depth of influence of the impact rolling.A relationship was developed between post‐compaction S‐wave velocity and Dry Density Ratio (DDR) that formed the basis of a viable geotechnical verification strategy for the ground improvement works on the larger brownfield site. Electromagnetic and advanced surface wave geophysics, combined with innovative ground improvement methods by rolling dynamic compaction, represent an advance over current practice for brownfield site development.

A microelectromechanical system digital 3C array seismic cone penetrometer

A digital 3C array seismic cone penetrometer has been developed for multidisciplinary geophysical and geotechnical applications. Seven digital triaxial microelectromechanical system accelerometers are installed at 0.25-m intervals to make a 1.5-m-long downhole seismic array. The accelerometers have a flat response up to 2 kHz. The seismic array is attached to a class 1 digital seismic cone, which measures cone tip resistance, sleeve friction, pore-pressure, and inclination. The downhole 3C array can be used together with impulsive seismic sources and/or high-frequency vibrators that are suitable for high-resolution shallow applications. Results from two field experiments showed that a good data quality, including a constant source function within an array, and a dense depth-sampling allowed robust estimation of seismic velocity profiles in the shallow subsoil. Using horizontal and vertical seismic sources, downhole 9C seismic array data can be easily acquired. The quality of the shear-wave data is much superior when the surface seismic source is a controlled, high-frequency vibrator in stead of a traditional sledge hammer. A remarkable correlation in depth, in a fine scale, between low-strain seismic shear wave velocity and high-strain cone tip resistance could be observed. The array measurements of the full-elastic wavefield and the broad spectral bandwidth are useful in investigating frequency-dependent seismic wave propagation in the porous near-surface soil layers, which is informative of the in situ fluid-flow properties. Stable estimates of dispersive seismic velocity and attenuation can be obtained.

Development of a Spray Characterization Experimental Facility

Abstract In the recent years, development of alternative jet fuels is gaining importance owing to the demand for diversifying fuel and cleaner combustion. Liquid fuels have high volumetric energy content and ease of handling therefore preferred by the aviation industry. However, liquid fuels add additional complications in combustion process in thrust generation due to the needed preparatory steps of atomization and vaporization. Alternate jet fuels then must meet the vital needed requirements such as rapid atomization, vaporization, quick re-ignition at high altitude, stable combustion before being used. At TAMUQ - Micro-Scale Thermo Fluids Laboratory (MSTF), an experimental facility is designed and developed to carry out a detailed investigation on the spray characteristics of jet fuels at different injection conditions. The spray characteristics such as droplet size, velocity and spray cone angle are investigated at different injection pressures. These details are obtained using the state-of-the-art non-intrusive laser diagnostics techniques. Experimental techniques involving both point-wise as well as plane-wise measurements are planned using the Phase Doppler Particle Analyzer (PDPA) and Global Sizing Velocimetry (GSV) respectively to obtain the spray characteristics. Initially, water is used to tune and establish experimental parameters in TAMUQ spray characterization facility followed by the conventional jet fuel, JetA1. The spray characteristics of water will then be compared with that of JetA1 fuel. This facility will later be used to study the spray characteristics of different gas-to-liquid (GTL) fuels as part of the on-going Qatar Science and Technology Park (QSTP) funded project involving Texas A&M at Qatar (TAMUQ), German Aerospace Laboratory (DLR), and Rolls-Royce (UK). The main objective of this work is to support the initial phase of the QSTP funded project. The spray characterization facility developed at TAMUQ will help to explore the potential of GTL fuels as an environmental friendly, alternate jet fuel.

Characterization of Norwegian marine clays with combined shear wave velocity and piezocone cone penetration test (CPTU) data

A database of research-quality piezocone cone penetration test (CPTU) and shear wave velocity, Vs, information for Norwegian marine clays has been assembled to study the small-strain stiffness relationships for these materials and to examine the potential use of CPTU and Vs data in combination for the purposes of characterizing these soils. Data for sites where high-quality block sampling was carried out have mostly been used. Improvements have been suggested to existing correlations between the small-strain shear modulus, Gmax, or Vs and index properties for these soils. Recent research has shown that CPTU corrected cone tip resistance, qt, and especially the pore pressure measured during CPTUs, u2, and Vs can be measured reliably and repeatably and are not operator or equipment dependant. Therefore, a new soil classification chart involving the normalized cone resistance, Qt, and normalized shear wave velocity, Vs1, or Vs1 and Δu/[Formula: see text] (where u is the pore-water pressure and [Formula: see text] is the in situ vertical effective stress) is presented. Using this chart it is possible to clearly distinguish between clays of different overconsolidation ratios (OCRs).

On the velocity field structure of jet streams and eddies in the ocean

The new velocity-based feature model, called streamlets model, is proposed for objective analysis of the three-dimensional velocity structure of jets and eddies. Streamlets comprise stream-coordinates, based on streamlines of maximum velocity as an axis, and vertical velocity cross sections, defined as an inclined velocity cone with elliptical base. Assimilation of velocity measurements is converted to fitting this cone to the available data. The proposed model is justified using the concept of coherent structures. We corroborate streamlets with observations of real oceanic jets and eddies using the Acoustic Doppler Current Profiler.