True Bearing Research Articles

The effect of the balloon on balloon-borne infrasound measurements

Deploying acoustic sensors on free-flying, long-living balloons helps to reach the areas not accessible with the traditional ground-based sensors, reduce flow noise, and improve characterization of various infrasound sources. In particular, instrumented balloons can potentially increase the infrasonic detection range and the early warning lead time for natural hazards, such as tornadoes and avalanches. When assessing the capabilities of balloon-borne infrasonic sensors and interpreting the measurements, it is important to recognize that the balloon inevitably distorts both signals and the ambient infrasound field by scattering the incoming sound. Measurement distortions due to a nearby compact scatterer prove to be rather different from the well-understood effect of a rigid boundary on ground-based sensors. Using the recently developed theory of sound scattering by thin, prestressed elastic shells [O. A. Godin, J. Acoust. Soc. Am. 154, 3223–3236 (2023)], this paper quantifies the effects of hot-air and helium balloons on acoustic pressure and oscillatory velocity. It is found that balloon-borne vector sensors are more susceptible to the distortions than pressure sensors, leading to large differences between the apparent and true source bearing and directionality. Possible approaches to compensate for the distortions and retrieve the free-field acoustic quantities will be discussed.

Investigation on the tensile properties of PtAl and PtReAl coated Ni3Al-based single crystal superalloy

Tensile tests of uncoated, diffusion Pt-aluminide (PtAl) coated and Re modified PtAl (PtReAl) coated Ni3Al-based single crystal superalloy were conducted at room temperature (RT) and 1100 °C to investigate the effect of coating on the tensile behaviors and the cracking mechanism. The results revealed that the PtAl and PtReAl coatings had significantly impaired the ultimate tensile strength of the superalloy by about 10% at room temperature, ascribed to the decreasing true bearing section of the coated specimens caused by the cracking of the brittle coatings. At 1100 °C, the PtAl and PtReAl coating improved the oxidation resistance and ductility of the superalloy. However, due to the low high-temperature strength of the coatings, the yield strength and the ultimate tensile strength of the PtAl coated superalloy showed a reduction of about 19% and 17% when compared to the uncoated superalloy. Moreover, the PtReAl coated specimen presented relatively lower strength than PtAl coated specimen, which is attributed to the internal oxidation of the Re-rich layer during the tensile test process at 1100 °C.

Bearing performance of high-strength bolted corrugated steel longitudinal seams

The assembly-type corrugated pipes have been widely used in underground pipeline construction owing to their rapid construction speed and strong adaptability to deformation. However, research with respect to the bearing performance and design methods of their longitudinal seams is lacking. In this study, axial compression tests were conducted on a single high-strength bolted seam of longitudinal seams of galvanised middle-wave corrugated steel plate structures to investigate the damage characteristics and bearing performance of the seams in different failure modes. A finite element analysis was also conducted to verify the test results and perform parametric analysis. The results showed that, to realise the maximum seam strength, the plate thickness should be matched to the bolt diameter. The torque coefficient hardly affects the ultimate bearing performance of the longitudinal seam, and the ultimate bearing capacity of the plate bearing failure seam is significantly influenced by the slip resistance coefficient. With the increase in waveform, the bearing capacity of seams increased by approximately 8.8% and 17.1% for the bearing failure of the plate, while it increased only slightly for bolt shear failure mode. Finally, several codes of bearing capacity calculation methods were compared with the test and simulation results. The revised Eurocode BS EN 1993-1-8:2005 accurately reflects the true bearing performance of corrugated steel plates with high-strength bolted connections. This study provides relevant reference data and design recommendations for seams that are easily overlooked in the design of assembly-type corrugated pipe projects.

Ship collision avoidance behaviour recognition and analysis based on AIS data

A novel approach is proposed to automatically identify the ship collision avoidance behaviour from ship trajectories based on an improved Sliding Window Algorithm. The approach has three main stages: (1) determining the ships’ obligations according to the Convention on the International Regulations for Preventing Collision at Sea (COLREGs); (2) assessing the rudder angle according to the true bearing of the target ship; (3) identifying the corresponding ship handling behaviour from the ship trajectory taking into account the Rate of Turn and its derivative based on the Sliding Window Algorithm. Four typical encounter scenarios are studied to demonstrate the feasibility and effectiveness of the proposed method. The approach is then applied to near collision scenarios identified in the maritime traffic off the continental coast of Portugal, which allowed the characterization of the relative and spatial distributions of the locations at which the ships take evasive manoeuvres. The results show that the approach can be applied to accurately detect the ship collision avoidance behaviour from Automatic Identification System trajectory data, and the characterization of the collision avoidance behaviour can potentially be used by situational awareness systems and as the basis for ship collision avoidance decision-making.

Analysis of the Protection Performance of Face Guard for Large Mining Height Hydraulic Support

With the increase of mining height, the problem of coal wall spalling in the working face gradually worsens. Hydraulic support and its face guard structure are the key pieces of equipment to restrain the coal wall spalling. However, at present, the hydraulic jack is mostly considered as rigid in the analysis of protection mechanism. This simplification cannot effectively reflect the true bearing state of the face guard. In order to improve the accuracy of analysis, this study considers the face guard jack as a flexible spring and establishes a rigid-flexible coupling analysis model of the face guard mechanism. First, based upon the multibody dynamics software ADAMS®, the multibody numerical model of the face guard of the hydraulic support was established. The influence of the two kinds of structures on the coal wall disturbance was analyzed and compared. Then, the rigid model was meshed. The hydraulic jacks were equivalent to the spring system, and the rigid-flexible coupling model was established. Based upon the application load on different positions of the rigid-flexible model, the load-bearing characteristics and hinge point force transfer characteristics of the two face guards were analyzed. The results show that the support efficiency of the integral type was higher than that of the split type. In the vertical support attitude, the dynamic disturbance of the coal wall, produced by the two kinds of face guards, was small. The four-bar linkage effectively improved the ultimate bearing capacity of the integral face guard. The results provide theoretical support for the design and optimization of the face guard.

EXPERIMENTAL STUDY ON BEARING CAPACITY OF DANGEROUS AND/OR OLD PRE-STRESSED CONCRETE BOX GIRDERS

In order to obtain the true bearing capacity of dangerous and old pre-stressed concrete box girder bridges, experiments on flexural and shear bearing capacity of full-scale dangerous and old pre-stressed concrete small box girders are conducted to study the mechanical degradation behavior of dangerous and old pre-stressed concrete box girders. Through the residual bearing capacity test of the full-scale prefabricated box girder, the load, deflection, strain and crack width of the test girders are measured and analyzed. The residual bending and shear ultimate capacity and stiffness of the small box girders are analyzed. The bending and shear behavior and failure mechanism of precast box girders in danger are obtained. The comparisons between the results of full-scale test and the calculated value of bearing capacity and also the design value of the internal force of I-Class highway are operated to analyze the actual performance of the small box girder made of dilapidated concrete. The damage reduction coefficient is introduced to establish the formula of ultimate bearing capacity of the girder. The test results stated that the structural damage affected the bearing performance of this box girder. The deflection of the test girder in the uncracked stage did not meet the proof stiffness requirements under the variable load of highway bridge. The calculated results of the flexural bearing capacity are basically identified with the result from full scale flexural test, which is 70% higher than the design bending moment by the internal force of the main girder. The results of full-scale shear tests are respectively 32% and 37% higher than the internal shear design values of the girder. The formulas with damage reduction coefficient for calculating the bending and shearing capacity of the concrete box girders is applicable to evaluate the bearing capacity of the dilapidated concrete girders with more accurate results, which can provide a reference for the evaluation and maintenance of massive existing small concrete box girders in China.

Bearing capacity of strip footings on sand over clay

Estimation of the bearing capacity of shallow foundations on layered soil profiles, such as a sand layer of finite thickness over clay, is mainly based on empirical models resulting from the interpretation of experimental test results. While it is generally accepted that such models may be applicable to soil properties and footing geometries outside the range tested experimentally, they offer limited insights on how the assumed failure mechanism affects their range of application. In particular, the contribution of the sand layer to the overall capacity is accounted for via simple considerations, which are valid only for a specific range of problem parameters. This paper addresses the estimation of the undrained bearing capacity of a rigid strip footing resting on the surface of a sand layer of finite thickness overlying clay, using finite element limit analysis (FELA). The rigorous upper and lower bound theorems of plasticity are employed to bracket the true bearing capacity of the footing, and identify the geometry of possible failure mechanisms. Insights gained from FELA simulations are used to develop a new simple bearing capacity model, which captures the variation in shear resistance from the sand layer with the dimensionless undrained strength of the clay layer. The proposed model provides results that are in close agreement with published experimental studies, and allows treating simple problems, such as the design of working platforms, without having to resort to numerical simulations.

Effect of acoustic horizontal refraction on DOA estimation with a single vector hydrophone

The effect of horizontal refraction (HR) on DOA estimation with a single vector hydrophone is studied. It has been demonstrated in a previous study that HR may bring about a significant deviation between the true bearing of the source and the direction of time-averaged sound flux at the receiver point, i.e., DOA estimation error. [J. Tang et al., 2018, 43(2), ACTA ACUSTICA (in Chinese)]. In the present work, the DOA estimation error in a more realistic scenario is studied, more precisely, source signals are considered to be wide-band instead of time-harmonic, and meanwhile ambient noise is added to the received signal. The ocean waveguide used in simulations is a 3D version of the standard ASA wedge, which implies that the HR considered in this work is raised from multiple reflections between a horizontal sea surface and a sloping sea bottom. The results of this work shall offer some reference to DOA estimation in circumstances with strong HR effects.

Methods for studying water characteristics and the spatial orientation of vector-scalar module

The results of natural studies of the methods for simultaneous measurements of the speed of sound in water and water temperature, as well as the depth, true bearing, and orientation of vector-scalar antenna in three-dimensional space, are reported. The tests were performed in the towing mode using a portable multifunctional complex, including hydrophysical, orientation, and direction finding units. The complex is recommended to be included in the composition of stationary or towed scalar or vector-scalar antennas.

Error Analysis on Bearing Estimation of a Towed Array to a Far-Field Source in Deep Water

Multipath arrivals received by a towed array with different arrival angles result in a bearing estimation error (BEE) when conventional beamforming is used in the real ocean waveguide. This paper investigates the errors based on simulated data, focusing on their dependence on the range and bearing of a far-field broadband source. The BEE varies periodically with range, reaching local minima and local maxima at the edges of convergence zones (CZs). The estimated source bearing always lies between the true source bearing and the broadside direction of the towed array. The physical mechanism is analyzed by using normal-mode theory for theoretical interpretation and the ray method for perceptual analysis. Based on conventional beamforming, the approximate analytical solution of the beam-forming output is derived in terms of normal modes and can predict the BEE quantitatively. The ray trace is used to illustrate the range dependence. The BEEs for different ocean depths are also discussed and the results can be used as auxiliary information for source localization.

Investigation of horizontal refraction on Florida Straits continental shelf using a three-dimensional Gaussian ray bundling model.

Acoustic transmission loss measurements from the calibration operations (CALOPS) experiment for the Shallow Water Array Performance (SWAP) program included horizontally refracted returns that were as much as 30° away from the true bearing between source and receiver. In many cases, the in-shore refracted path was 20 dB stronger than the true bearing path. In this study CALOPS transmission loss measurements at 415 Hz are compared to predictions from a three-dimensional Gaussian ray bundling model. The geoacoustic model that provides good model-data comparison is consistent with the geologic and sediment core data collected at the location but differs slightly from the bottom model used at lower frequencies (206 and 52.5 Hz) in a previous study.

Simulation studies on static thermal behaviour of true elliptical and orthogonally displaced non-circular journal bearing

Purpose The current trend of modern industry is to use machineries which rotate at high speed along with the capability of carrying heavy rotor loads. This paper aims at static thermal analysis of two different profiles of non-circular journal bearings – a true elliptical bearing and orthogonal bearing. Design/methodology/approach The Reynolds equation has been solved through finite difference method to compute the oil film pressure. Parabolic temperature profile approximation technique has been used to solve the energy equation and thus used for computation of various bearing performance characteristics such as thermo-hydrodynamic oil film pressure, temperature, load capacity, Sommerfeld number and power loss characteristics across the bearing. The effect of ellipticity ratio on the bearing performance characteristics has also been obtained for both the elliptical and vertical offset bearing using three different commercially available grades of oil (Hydrol 32, 68 and 100). Findings It has been observed that the thermo-hydrodynamic pressure and temperature rise of the oil film is less in orthogonal bearing as compared to the true elliptical bearing for same operating conditions. The effect of ellipticity ratio of non-circularity on bearing performance parameters have been observed to be less in case of elliptical bearing as compared to orthogonal bearing. It has been concluded that though the rise in oil film temperature is high for true elliptical bearing, but still it should be preferred over orthogonal profile under study, as it has comparably good load-carrying capacity. Originality/value The performance parametric analysis will help the designers to select such kind of non-circular journal bearing for various applications.

Multifunctional portable hydrophysical module with units for orienting and estimating true bearing

A portable hydrophysical module, matched with orientation and direction finding units, has been developed and investigated. This module is aimed at measuring simultaneously the speed of sound, water temperature, and hydrostatic pressure at the module horizon and estimating true bearing and the module orientation in the three-dimensional space.

Influence of backfill on coal pillar strength and floor bearing capacity in weak floor conditions in the Illinois Basin

This paper discusses the current theoretical design equations associated with foundation design in the Illinois Basin, as well as the benefits of utilizing high density backfill in a numerical model, to improve pillar and floor stability. Based upon the results, Vesic’s bearing capacity solution for a two layered soil tends to underestimate the true bearing capacity of a foundation, especially at higher friction angles and when footings are placed in close proximity. Minimizing the distance between adjacent foundations has shown an improvement in the ultimate bearing capacity of a foundation; however, placing the foundations in too close proximity has shown the foundations may behave as a single foundation and undergo appreciable settlement. A 10–40% increase in pillar strength and ultimate bearing capacity can be expected when a cohesive fill is used between 25 and 75% fill of the mined height, respectively. The non-cohesive nature of the simulated backfill showed little influence on increased pillar strength, even at higher fill ratios. It was determined, that as the shearing resistance, tensile strength and stiffness of the backfill are reduced, increases in coal pillar strength is due more to the confinement aspect of an underground mine rather than the strength properties of the material itself. A methodology for analyzing the plastic flow characteristics of a coal pillar and a footing using FLAC3D has also been presented herein.

True 3D Weight Bearing CT Imaging for Foot and Ankle

: Foot and ankle surgery is a sub-specialty of orthopedics and podiatry that deals with the treatment, diagnosis and prevention of disorders of the foot and ankle. For the first time, physicians can get three-dimensional, weight bearing images of the foot and ankle with the pedCAT system. The pedCAT uses cone beam volumetric tomography to reconstruct the foots bony anatomy in its true physiological position within minutes. The pedCAT is a compact device that requires minimal radiation shielding, which means it could fit in a primary care podiatrist's office as easily as it could in a large imaging center. The pedCAT is manufactured by CurveBeam. CurveBeam was founded in 2009 with the primary mission of adapting cone beam volumetric tomography technology to imaging all body extremities. Over the past decade, CBVT has revolutionized oral and maxillofacial care. Three-dimensional scans of the skull have become an essential tool in diagnosis and treatment planning, especially for orthodontics and dental implants. The pedCAT is expected to transform the fundamentals of diagnostic imaging for the foot and ankle specialty by providing an ideal starting point to evaluate and treat a patients foot condition. The pedCAT is easy to use for both the doctor and the patient. The patient steps onto a platform and the gantry closes behind him. The physician pushes a single button, and the pedCAT scans one foot in less than 20 s or both feet in less than 40 s in weight bearing or non-weight bearing positioning. The manufacturer estimates the radiation dose delivered to the patient to be slightly higher than a similar plain X-ray. CubeVue, the accompanying software, stitches together the slices to create an exact digitized replica of the foot and ankle in less than three minutes. Using CubeVue, the physician can get an unobstructed view of the foot from any angle, rotate and navigate the 3D data, and make exact measurements. The physician can scroll through the slices, which can be as thin as 3 mm, in any direction. The pedCAT? , first in-office TRUE 3D weight bearing CT for the foot and ankle, helps optimize treatment planning for our patients. Via this low dose radiation option, the pedCAT? assesses clinical conditions including, but not limited to, fractures, dislocations, arthritic joints, deformity and for quicker diagnosis, evaluation and treatment planning. The patient experience benefits include: in-office and on-site compact imaging; TRUE weight bearing and non-weight bearing 3D imaging for one or both feet; capture unprecedented diagnostic information not seen in regular x- rays; easy to use visualization software that adds a new dimension to diagnosis and evaluation; fast acquisition of 3D data allows you to start your treatment planning in minutes; If needed, we can confidently plan surgeries with precision and speed.

A Study on the Influence of Waviness Error to a Hydrostatic Bearing for a Crankshaft Pin Turner

This article describes a theoretical analysis of a hydrostatic journal bearing for a crankshaft pin turner by considering the waviness error of the journal and bearing. The authors found adequate design parameters to operate the crankshaft pin turner bearing. The flow rate, radial clearance, and eccentricity were selected as the basic design parameters. The load-carrying capacity of the bearing as a function of the design parameters was studied in the case of a true circular journal and bearing. The influence of the waviness error on the load-carrying capacity was then investigated; cosine functions were selected for the waviness functions. As a result, the load-carrying capacity varied according to the amplitude and phase angle of the waviness functions. Thus, it was found that the influence of the waviness error is a significant factor in analyzing lubrication characteristics. Run-out accuracy analysis method according to the waviness phase angles of the journal and bearing was suggested. It was found that the phase angles between the bearing load wave and load-carrying capacity wave are important factors that affect the running accuracy in addition to the amplitude of waviness error.

Designing nonuniform linear arrays to maximize mutual information for bearing estimation

Estimating the bearing of a narrowband sound source using a towed horizontal array is a common array processing problem. This paper designs nonuniform linear symmetric arrays of fixed apertures for estimating the bearing of a sound source. Specifically, the hydrophone spacings for a symmetric linear array are chosen to maximize the upper bound on the mutual information between the true bearing and the estimated bearing in spatially white noise. The arrays maximizing the mutual information while nulling the forward endfire direction look significantly different from the uniform arrays commonly used in towed systems. Arrays maximizing mutual information are helpful when bearing estimation is considered as a quantization problem to assign the source to the correct partition. The optimal partitions for the array are designed using the Lloyd algorithm with an inner product distortion metric based on maximizing the likelihood function of the observations. In these approaches, increasing the mutual information and optimizing the partitions should reduce the probability of error (P(e)) in choosing the partition containing an unknown source. Simulation results with MAP and ML estimators demonstrate that the optimum arrays and partitions proposed here have a much lower P(e) than the uniform array and uniform partitions.

Quantifying the Use of Dynamics in Western Keyboard Music: Lessons and Problems

Ladinig and Huron's (2010) investigation of the relationship between mode (major-minor) and dynamics in Classical and Romantic piano music indicated higher levels of dynamics for compositions from the Classical period but only in major-mode pieces. This was contrary to the expectation that minor mode pieces from the Romantic era would be louder because romantic composers may have intended to convey seriousness, passion or even aggression, rather than sadness. Although the methodology was carefully crafted to enable necessary control for a quantitative study, it also contributed to the questionable relevance of the results. It is arguable whether the chosen repertoire is typical, whether initial markings in the score have a true bearing on the dynamic characteristics of a piece and whether notated dynamics are reliable data due to historical notation conventions and later editorial practices.

Maximizing mutual information in horizontal linear arrays.

Estimating the bearing of a sound source using a towed horizontal array is a common array processing problem. In a passive sonar system, it is common to null sources from the forward endfire direction to eliminate the noise of the towing vessel. This research designs linear nonuniform symmetric arrays of a fixed aperture for estimating the bearing of sound source. Specifically, the hydrophone spacings for a symmetric linear array are chosen to maximize the upper bound on mutual information between the true bearing and the bearing estimate in white noise. The arrays’ maximizing the mutual information while nulling forward endfire look significantly different from the uniform arrays commonly used in towed systems, and also differ from arrays designed to minimize spacing redundancy. Arrays maximizing mutual information are helpful when bearing estimation is considered as a quantization problem to assign the source to the correct partition. In this approach, increasing the mutual information should reduce the probability of error (Pe) in choosing the partition containing an unknown source. Simulation results demonstrate that the optimum arrays proposed here have much lower Pes than the uniform array. [Work funded by ONR code 321US.]

Measurements of three-dimensional propagation in a continental shelf environment

Although a significant amount of theoretical and numerical modeling effort has been put into the study of three-dimensional (3D) acoustic propagation on a coastal wedge, including the development of the ASA 3D benchmark problem set, there have been few observations of the predicted 3D propagation effects. Significant horizontal multipath arrivals were observed in a pair of acoustic transmission tests on the continental shelf off the east coast of Florida in September 2007 and February 2008. For many transmissions, arrivals were received coming from nearly the global positioning system (GPS) bearing of the ship, as well as up to 30 deg inshore of the true bearing. The inshore path was up to 25 dB stronger than the direct path in some cases. The experimental waveforms transmitted included continuous-wave transmissions ranging in frequency from 24 to 415 Hz as well as wideband linear frequency modulation pulses (20-420 Hz). Horizontal multipath arrivals were observed for source ranges from 10 to 80 km, source depths of 20 and 100 m, and along several different bearings (inshore and along the 250 m isobath). It is a conclusion of this paper that the bearing bias and multiple horizontal arrivals are the result of 3D propagation due to the local shoaling bathymetry.