Mach Effect Research Articles

Effect of Groundwater Level Rise on the Critical Velocity of High-Speed Railway

The increasing frequency of extreme rainfall is leading to a rise in groundwater levels in coastal areas, significantly affecting high-speed railway operations. To address this concern, this study developed a 2.5-dimensional finite element model of a coupled track-embankment-ground system based on Biot’s porous media theory to analyze the effect of groundwater level rise on the critical velocity of high-speed railways and vibration responses. The findings reveal a consistent decrease in the critical velocity of high-speed railways with rising groundwater levels. Particularly, the increase in groundwater levels within the embankment significantly influences the critical velocity compared to a similar rise in the foundation’s groundwater level. Furthermore, deformations induced by passing trains significantly increase as groundwater levels rise. Specifically, when the groundwater level rises from the foundation bottom to the subgrade surface, subgrade surface deformation increases by approximately 55%. As trains approach the critical velocity, significant vibration phenomena, known as the “Mach effect,” occur at the foundation surface. Importantly, as groundwater levels rise, the “Mach effect” intensifies. Analyzing the vibrating frequency spectrum of the displacement response demonstrates a substantial increase in vibration amplitude, particularly in the high-frequency region, as groundwater levels rise. This study highlights that the rise in groundwater level not only amplifies vibrations but also extends the propagation of high-frequency vibrations, underscoring the importance of effective embankment waterproofing in controlling track vibrations.

The Diagnostic Relevance and Interfaces Covered by Mach Band Effect in Dentistry: An Analysis of the Literature.

This work surveyed how the Mach band effect was mentioned in the dental literature and provided a qualitative assessment of diagnostic relevance and interfaces covered. PubMed, Scopus, and Google Scholar were queried in mid-Jan 2022. The search string was (“mach band effect” OR “mach effect”) AND (dental OR oral OR tooth OR teeth OR maxillofacial OR orofacial). All publications returned by the searches were screened. Exclusion criteria included irrelevance (e.g., dealing with “Mach effect” that was non-radiographic or non-dental) and not written in English. Reference lists of returned publications were manually searched to identify potentially missed papers. For each included publication, the following parameters were recorded: any presentation of radiographic images showing a Mach band effect, direct investigation of the effect, relevance to which structural interfaces, diagnostic relevance, and in which parts of the publication Mach band effect was mentioned. Seventy-seven publications were included and analyzed. The majority of the publications mentioned the Mach band effect in the Discussion section about its diagnostic relevance to caries detection at the enamel-dentinal junction and the interface between restorative material and tooth structure. Eight of them presented radiographic images showing a Mach band effect. Three of them investigated the Mach band effect. Dental publications seldom covered the Mach band effect. When they covered it, most of them only mentioned it in the Discussion section without actually investigating it.

Graphene\u2019s non-equilibrium fermions reveal Doppler-shifted magnetophonon resonances accompanied by Mach supersonic and Landau velocity effects

Oscillatory magnetoresistance measurements on graphene have revealed a wealth of novel physics. These phenomena are typically studied at low currents. At high currents, electrons are driven far from equilibrium with the atomic lattice vibrations so that their kinetic energy can exceed the thermal energy of the phonons. Here, we report three non-equilibrium phenomena in monolayer graphene at high currents: (i) a “Doppler-like” shift and splitting of the frequencies of the transverse acoustic (TA) phonons emitted when the electrons undergo inter-Landau level (LL) transitions; (ii) an intra-LL Mach effect with the emission of TA phonons when the electrons approach supersonic speed, and (iii) the onset of elastic inter-LL transitions at a critical carrier drift velocity, analogous to the superfluid Landau velocity. All three quantum phenomena can be unified in a single resonance equation. They offer avenues for research on out-of-equilibrium phenomena in other two-dimensional fermion systems.

Bucknell Undergraduate Engineers Enhance Novel Instrument to Observe the Mach Effect

Bucknell Undergraduate Engineers Enhance Novel Instrument to Observe the Mach Effect

Propagation behaviour of a hemispherical blast wave on a dome roof

Dome structures are often employed for industrial buildings and may be potential targets of terrorist attacks or accidental explosion. Military design manuals that are commonly used for structural design practice are based on the assumption that the blast wave reflects on an infinite or finite flat surface. These semi-empirical formulae ignore the blast wave propagation behaviour on a finite and variable-curvature reflector. The purpose of this research work is to estimate the blast load on dome structures during an external explosion. To achieve this objective, two laboratory-scale spherical dome structures were tested experimentally with 11 different blast cases. Following the experimental analysis, numerical parametric analysis based on ANSYS/AUTODYN was carried out to study the propagation and reflection on dome roofs. In addition, the performance of the Mach effect, reflection effect, diffraction effect, clearing effect and decay coefficient of the blast wave on the dome roof were investigated for different structural and explosion parameters. Based on this, a series of empirical equations are proposed to describe the temporal and spatial blast load distribution on a dome roof mounted on a supporting structure. This new load model described in the paper has been validated as it is able to predict the results of the experimental measurement on dome structures within experimental error.

Study on the Mach Reflection of Detonation Waves

In order to know the basic characteristics of Mach relection effect, computing and experimental research on Mach reflection is conducted which is likely to formed in the course of the explosion which will break buildings and other objects and cause the loss of injuries and property damage.Firstly, the paper conducts comprehensive compare and analysis, and concludes influence factors accounting to the deviation of calculated results. Secondly,with the improved Whitham's method, relevant parameters of Mach effect and detonation wave is gained.Finally,by conducting computation based on the experiment data,the paper gets the result reasonable,and hope that there will be more novel ways of thinking the Mach so as to drive research progress.

Mach-Effect thruster model

The Mach-Effect thruster is a propellantless propulsion concept that has been in development by J.F. Woodward for more than two decades. It consists of a piezo stack that produces mass fluctuations, which in turn can lead to net time-averaged thrusts. So far, thrust predictions had to use an efficiency factor to explain some two orders of magnitude discrepancy between model and observations. Here, a detailed 1D analytical model is presented that takes piezo material parameters and geometry dimensions into account leading to correct thrust predictions in line with experimental measurements. Scaling laws can now be derived to improve thrust range and efficiency. An important difference in this study is that only the mechanical power developed by the piezo stack is considered to be responsible for the mass fluctuations, whereas prior works focused on the electrical energy into the system. This may explain why some previous designs did not work as expected. The good match between this new mathematical formulation and experiments should boost confidence in the Mach effect thruster concept to stimulate further developments.

The Mach stem phenomenon for shaped obstacles buried in soil

The paper investigates the explosion characteristics of a below ground event of an explosive charge in proximity to a rigid cylindrical obstacle. The two-dimensional study simulates a line explosive and a parallel long cylindrical structure. The investigation shows that the unloading branch has a negligible effect on the peak pressure envelope whereas shear behavior and explosives burning have a considerable effect and should not be disregarded. The effect of the soil's equation of state and especially the full locking parameter on the pressure distribution on an obstacle has been studied. At a short standoff distance where a steep pressure growth beyond the full compaction point is developed, the pressure distributions envelope shows three maxima values that are located at some distance away from the axis of symmetry. It is different than the common single peak along the axis, in the case of a distant explosion. This effect is more pronounced for a medium having sharper pressure growth in the EOS beyond the full compaction point and for smaller charge standoff distances. The pressure distributions analysis indicates that the appearance of second (absolute-primary) and third (secondary) peaks are caused by the Mach stem effect appearing in a soil medium with full locking. The secondary peak pressure envelope maximum corresponds to the secondary Mach stem phenomenon that does not appear in the case of a planar wall, where the incident angle depends on the wave front curvature only.

Characteristics of Mach effect induced by oblique wave-wave interactions of internal solitary waves in ocean

The Mach effect induced by the oblique wave-wave interactions of internal solitary waves is a special phenomenon of the ocean and is also the main reason of generating a large amplitude internal solitary wave, while they can cause it damage and even crash as the ocean engineering structures or underwater vehicles encounter the internal solitary wave with a large ampiltude in the ocean. In order to simulate the oblique interaction of internal solitary waves in the thermocline marine environment and control the Mach effect in the laboratory, two vertical bottomless barrels are placed in the fresh/saline water’s two-layer fluid. So the mixed fresh/saline water region is called the density thermocline of the marine. Keeping exchange of water under the barrel’s bottoms is to facilitate the formation of the mixed region height difference in the inner and outer parts of barrels. And then remove the two barrels smoothly and quickly, so that the mixed fresh/saline water region’s gravitational collapse motion can be made use of to generate two rows of internal solitary waves. They will occur the oblique wave-wave interaction in their propagating intersection area. The experimental results showed that two rows of solitary wave oblique interaction depends on the stratification environment, the distance between the two barrels and the amplitude and phase of two solitary waves. It has been vertfied that the above method can effectively control the generation of Mach effect in the stratified fluid tank. Further analysis showed that the Mach effect induced by the oblique interaction of internal solitary waves will lead to remarkably increasing amplitude in correspondence with its raising propagation velocity, whose direction is controlled by the amplitude difference between two internal solitary waves, and the greater amplitude difference will bring on the larger Mach effect’s critical angle. Through testing the theoretical models including KdV’, BO’ and MCC’s equations to compare with the experimental results , the adaptability of the Mach effect to the nonlinear theoretical models is verified by experiments.

Theory of a Mach Effect Thruster I

The Mach Effect Thruster (MET) is a propellant—less space drive which uses Mach’s principle to produce thrust in an accelerating material which is undergoing mass—energy fluctuations, [1]-[3]. Mach’s principle is a statement that the inertia of a body is the result of the gravitational interaction of the body with the rest of the mass-energy in the universe. The MET device uses electric power of 100 - 200 Watts to operate. The thrust produced by these devices, at the present time, are small on the order of a few micro-Newtons. We give a physical description of the MET device and apparatus for measuring thrusts. Next we explain the basic theory behind the device which involves gravitation and advanced waves to incorporate instantaneous action at a distance. The advanced wave concept is a means to conserve momentum of the system with the universe. There is no momentun violation in this theory. We briefly review absorber theory by summarizing Dirac, Wheeler-Feynman and Hoyle-Narlikar (HN). We show how Woodward’s mass fluctuation formula can be derived from first principles using the HN-theory which is a fully Machian version of Einstein’s relativity. HN-theory reduces to Einstein’s field equations in the limit of smooth fluid distribution of matter and a simple coordinate transformation.

Numerical analysis of soil vibrations due to trains moving at critical speed

High-speed train induced vibrations of track structure and underlying soils differ from that induced by low-speed train. Determining the critical speed of train operation remains difficult due to the complex properties of the track, embankment and ground. A dynamic analysis model comprising track, embankment and layered ground was presented based on the two-and-half-dimensional (2.5D) finite elements combining with thin-layer elements to predict vibrations generated by train moving loads. The track structure is modeled as an Euler–Bernoulli beam resting on embankment. The train is treated as a series of moving axle loads; the embankment and ground are modeled by the 2.5D finite elements. The dynamic responses of the track structure and the ground under constant and vibrating moving loads at various speeds are presented. The results show that the critical speed of a train moving on an embankment is higher than the Rayleigh wave velocity of the underlying soil, attributed to the presence of the track structure and the embankment. It is found that the dynamic response of ground induced by moving constant loads is mostly dominated by train speed. While for the moving load with vibration frequency, the ground response is mostly affected by the vibration frequency instead of train speed. Mach effect appears when the train speed exceeds the critical speed of the track–embankment–ground system.

Flux Capacitors and the Origin of Inertia

The explanation of inertia based on “Mach's principle” is briefly revisited and an experiment whereby the gravitational origin of inertia can be tested is described. The test consists of detecting a small stationary force with a sensitive force sensor. The force is presumably induced when a periodic transient Mach effect mass fluctuation is driven in high voltage, high energy density capacitors that are subjected to 50 kHz, 1.3 kV amplitude voltage signal, and threaded by an alternating magnetic flux of the same frequency. An effect of the sort predicted is shown to be present in the device tested. It has the expected magnitude and depends on the relative phase of the Mach effect mass fluctuation and the alternating magnetic flux as expected. The observed effect also displays scaling behaviors that are unique to Mach effects. Other tests for spurious signals suggest that the observed effect is real.

Quantum Mach effect by Sagnac phase shift on Cooper pairs in rf-SQUID

The inertial drag on Cooper pairs in a rotating rf-SQUID ring leads to an asymmetry in the Hamiltonian potential able to modify the tunnelling dynamics. This effect is a Sagnac signature of Cooper pairs at a quantum level and it may probe the Mach effect influence on the wavefunction collapse.

Unique Fine Microstructures of Iron Caused by Intense Shearing under Shock Compression

Sample assemblies consisting of an iron rod and a concentric 2024-aluminum alloy cylinder were shock-treated by impaction of an iron flyer plate. Since the shock wave velocity of the rod is slower than that of the cylinder, oblique shock waves from the cylinder interact with the plane shock waves in the iron rod and form a conical region of plane loading in the front one-third of the rod. An ellipsoidal region, due to Mach effect, might even be formed in the next one-third. Outside of the conical region, intense shearing is anticipated. Microstructures of a longitudinal cross section of the recovered rod and Vickers hardness were axis-symmetric. The ellipsoidal region could not be seen in the cross section. However, outside of the region, fine microstructures were observed. These fine structures might be formed during the intense shearing in the high-pressure ε phase of iron and subsequent reverse transition to the normal α phase.

Visual illusions in the interpretation of the radiographic image

The human body is a complex of tissues of different radiographic densities. Overlapping shadows, differences in background density, subjective contour formation, and the parallax effect often produce a variety of optical illusions that exist only in the “mind's eye” and may be mistaken for significant pathology. Most of these phenomena are produced by the Mach effect, a consequence of the physiological process of lateral inhibition. Subjective contour formation is a “psychophysiological” phenomenon in which complete “structures” appear from minimal outlines. A parallax effect occurs if real structures contribute to the radiographic image. This review discusses the basic physiology involved in image reception and the formation of false images. Clinical consequences of the presence of Mach bands, background density effect, subjective contours, and real or physical phenomena are illustrated.

Interobserver Variability in Interpreting Radiographic Lucencies About Total Hip Reconstructions

Radiographs are commonly used to identify the loosened total hip reconstruction (THR), to plan revision surgery, and to evaluate long-term follow-up patients for study purposes. Interobserver variability was studied in an attempt to interpret 63 random follow-up films in a group of 93 patients eight to 12 years post-THR. Nine observations were made on the acetabular and femoral sides of the reconstructions on all films for a total of 567 observations. There was considerable disagreement in observations of the acetabular lucencies; a consensus of all three observers was obtained only 46% of the time. There was more uniform agreement among observers (87%) in analyzing the femoral side, although agreement was most frequent when there was no lucency. There was no difference in observer variables when greater lucencies were reported by one or more observers than when there were smaller lucencies. It was concluded that a single observer can reliably record a femoral observation of no lucency and, making allowances for the Mach effect, can reliably distinguish the presence or absence of a lucency. However, a single observer may not be able to make observations of acetabular lucencies with great reliability and, in contrast to femoral lucencies, a single observer may be less reliable in recording acetabular lucencies over 2 mm as compared with those under 2 mm.

On display of space filling atomic models in real-time

Earlier work on real-time display of planar polygonal three-dimensional object scenes is extended to the inclusion of repetitive curved surfaces. In earlier work the visible scene components were calculated and reduced to scan line encoded image segments to generate real-time cartoons. That work was limited to visible planar surface elements because of the display algorithms employed. Display time is limited to 33 ms so that scan-interlaced TV may be used. Curved surfaces would normally be approximated by a large number of facets; however, Mach effect's faceting of the surface will occur for all but the simplest cases. Point by point curved surface shading is examined in detail so that special hardware may be defined for displaying the visible surface parts in 33 ms. The hardware concepts employed can be extended to other simple curvatures that appear repeatedly in a visible scene. CONTENT INDICATORS: 3.13, 6.22, 6.35, 6.4, 3.89.

The metal-cement interface in total hip prostheses

Serial radiographs of 101 total hip arthroplasties were reviewed to evaluate the clinical significance of lucent zones at the femoral metal-cement interface. Such lucent zones were identified in 19 hip prostheses, but only in four was there clinical evidence of infection loosening of the prosthesis. The remaining 14 patients (15 prostheses) were followed for periods ranging from 18 months to 5 years; none had complications despite the development of these lucent zones. Microdensitometry confirmed the existence of a true lucent zone in most cases, but in several the apparent lucency was due to the Mach effect. While progressive widening of the lucent zone or a lucency measuring greater than 2 mm in width should prompt careful clinical evaluation for evidence of infection or loosening, our data indicate that such complications need not necessarily be present.

Two lesser known but useful signs of neonatal pneumothorax.

Two lesser known signs of neonatal pneumothorax are presented: the "large, hyperlucent hemithorax" sign and the "medial stripe" sign. In a review of 113 consecutive cases of proven neonatal pneumothorax, the large, hyperlucent hemithorax was the presenting sign in 29 and the medial stripe in 12 (25% and 11%, respectively). A left-sided preponderance of both signs but especially of the large, hyperlucent hemithorax remained unexplained. The practical significance of the signs, differential diagnosis, and influence of the Mach effect are described.

The Metal-Cement Interface in Total Hip Prostheses

Serial radiographs of 101 total hip arthroplasties were reviewed to evaluate the clinical significance of lucent zones at the femoral metal-cement interface. Such lucent zones were identified in 19 hip prostheses, but only in four was there clinical evidence of infection loosening of the prosthesis. The remaining 14 patients (15 prostheses) were followed for periods ranging from 18 months to 5 years; none had complications despite the development of these lucent zones. Microdensitometry confirmed the existence of a true lucent zone in most cases, but in several the apparent lucency was due to the Mach effect. While progressive widening of the lucent zone or a lucency measuring greater than 2 mm in width should prompt careful clinical evaluation for evidence of infection or loosening, our data indicate that such complications need not necessarily be present.