Magnification Effect Research Articles

Effect of Low Power Magnification on Total Occlusal Convergence Angles in Crown Preparation

Effect of Low Power Magnification on Total Occlusal Convergence Angles in Crown Preparation

Long-range, high-precision absolute distance measurement technology based on alternately oscillating optoelectronic oscillator

Absolute distance measurement plays an important role in many areas, such as aerospace and scientific research. Traditional measurement methods generally cannot meet requirements for long-range and high-precision at the same time. In this paper, an absolute distance measurement method based on alternately oscillating optoelectronic oscillator is proposed. This method places the distance to be measured in the loop of optoelectronic oscillator and takes advantage of accumulative magnification effect to achieve high accuracy. The measurement and the reference optoelectronic oscillators are established and selected by an optical switch, and a microwave switch is used to choose the high-order or low-order oscillating frequency. The high-order frequency and low-order oscillating frequency of the measurement and reference optoelectronic oscillators are measured in turn by frequency counter to calculate the loop lengths of two optoelectronic oscillators. The low-order frequencies are used to measure the fundamental frequency roughly and the high-order frequencies are used to calculate loop length precisely. Although the mode hopping occurs in the measurement process, it does not affect the loop length calculation by substituting the corresponding oscillating mode number. Note that the loop length measurement moments of two optoelectronic oscillators are different due to the switching order of optical switch and microwave switch. In order to calculate the absolute distance, which is the length difference between two optoelectronic oscillators at the same moment, the measured loop lengths should be averaged.In this way, systematic error accumulation caused by slow drift of environment can be eliminated, and this method does not need to control the length of reference optoelectronic oscillator. Meanwhile, the measurement system is simple. In the experiment, 1 km, 5 km and 8 km fibers are placed in a common part of the measurement and reference optoelectronic oscillators to simulate different long-range distances in space. A high-resolution optical delay line is placed in the measurement optoelectronic oscillator to verify the performance of the measurement system. The experimental results show that the measurement error is 3.5 μm with a 3.5 μm maximum standard deviation of each measurement distance at an emulated round trip distance of 6 km. The relative measurement accuracy reaches 5.8 × 10<sup>－10</sup>. This method provides a feasible idea for solving the technical problems of long-range and high-precision absolute distance measurement.

Real-Time and Long-Distance Measurement of Displacement Based on Optoelectronic Oscillator

A frequency-encoded real-time and long-distance displacement measurement method based on two cross-referencing optoelectronic oscillators (OEOs) is proposed and experimentally demonstrated. In the system, one OEO is used for reference, and the other is used for measurement. The initial distance is evaluated by the oscillation frequency and free spectral range of the OEO for reference. The small displacement is calculated by using the frequency of the intermediate frequency (IF) signal generated by mixing the two OEOs. The two OEOs with the same characters are placed in the same environment. This protects the displacement measurement from the influence of the variation of ambient temperature. A high measurement sensitivity, which improves the precision of the displacement measurement, is also implemented due to the accumulative magnification effect at high-order resonant frequency modes. In addition, the low frequency of the IF signal, which is far smaller than the oscillation frequency of the two OEOs, allows a cost-effective and real-time measurement by a frequency counter. The proposed displacement measurement method is demonstrated experimentally. When the sampling time is 1 ms, displacement measurement errors less than ±3.71 and $\pm 11.14~\mu \text{m}$ are realized at emulated distances of around 800m and 6 km, respectively. The real-time velocity and acceleration measurements are also implemented owing to the introduction of a time signal in the measurement process.

Low-frequency Topographic Amplification Effect of Lushan Earthquake Based on Three-dimensional Numerical Simulation

The study of the influence of terrain on ground motion is quantified as the amplification effect of terrain on ground motion. In this paper, we use the spectral element method to simulate the three-dimensional real terrain model, and select the aftershocks of the station ground motion observation records in the Lushan area as the source, and analyze the amplification effect of the three-dimensional topography on the ground motion of the Lushan earthquake in the low frequency range (1-5hz). In this paper, the Fourier model of the real terrain of Lushan and the half-space free model are used to calculate the Fourier amplitude spectrum. The results show that in the low frequency range, the ground fluctuations have a large variation, which will have complex effects on the propagation of seismic waves. Especially in the bulging mountain and depression terrain, the time course peak is large. In addition, this paper selects the mountain near the BXD station from the calculation area, and analyzes the terrain magnifying effect of the convex mountain. Under 2-3hz, the mountain slope near the source side has a magnification effect of 3-4 times.

An improved image mixed noise removal algorithm based on super-resolution algorithm and CNN

Based on the hardware and sensors of image acquisition, the noise in the image has been easily generated. In this paper, an improved method of image decompression has proposed the shortcoming of the above-mentioned hardware algorithm. The traditional filter desiccation algorithm can only remove one or two specific noises, and it is not effective for other types. We combine some excellent neural network models. In this paper, an image mixing noise removal algorithm based on convolution nerve has been mentioned. Aiming at realizing the super-resolution of the image, the deconvolution layer can be used only to enlarge the image. The magnification factor is the step of deconvolution. This paper aims to eliminate the interference of the image noise. The effect of magnification on the deconvolution layer is impossible. The results of experimental test show that the algorithm achieves a good noise removal effect and is suitable for various mixed noise images. The algorithm used in this paper improves the subjective visual effect and objective evaluation index.

Interplay of vortex and non-vortex beam components in a variable two-crystal cascade conical refraction.

In a two-crystal cascade conical refraction, a collimated light beam propagates along the optical axes of two biaxial crystals arranged in a series. In a variable cascade modification, the beam formed by the first crystal is imaged by a lens through the second crystal. Such an arrangement enables additional control over the cascade parameters and the output light beam properties. It is shown that the imaging stage of a variable cascade can drastically change the internal structure of the outgoing beam consisting of superimposed vortex and non-vortex components. In a degenerate case of two identical crystals, the conical refraction caused by the first crystal can be completely reversed by the second crystal, so that the output vortex component vanishes, and the input non-vortex light beam is restored. In sharp contrast, in a variable cascade, the vortex beam component does not vanish and, depending on the focal length of the imaging lens, can hold a significant fraction of the total beam power even in the apparently degenerate case. To describe the variable cascade, the existing theory of cascade conical refraction is complemented with a wave-optical description of the imaging stage, taking into account the effects of magnification and the focal length of the lens. The results of numerical simulations are in a good agreement with experimental observations. A concept of generalized cascade conical refraction is introduced.

Flow and thermal analyses of supercritical hydrocarbon fuel in curved regenerative cooling channel around cavity in rocket based combined cycle engine

Various studies in straight channels have been investigated to promote the development of regenerative thermal protection technique. However, the combined effects of curved structure and pyrolytic reaction of hydrocarbon fuel have not been adequately investigated. In this article, the effects of inlet temperature, unilateral heat flux and pyrolytic reaction on flow and heat transfer processes in a 90° curved channel around cavity are numerically analyzed in fluid-solid coupled and uncoupled models, considering variable thermophysical properties and chemical components. Results show that there is strong secondary flow around the corner of cooling channel and the vortices form a heat transfer deterioration region at the center of bottom wall which results in transverse temperature difference. With increasing inlet temperature, the vortices magnitude is increasing and the transverse nonuniformity of temperature decreases by 60.3%. And when the inlet temperature reaches the value with maximum pyrolytic rate, the increasing heat flux is mostly taken by the pyrolysis reaction which results in insignificant changes of vortices magnitude. The pyrolysis reaction intensifies the stratifications of pressure and density, which correspondingly strengthens the magnification effect of vortices around the corner and decrease the transversal temperature difference.

GW×LSS: chasing the progenitors of merging binary black holes

Are the stellar-mass merging binary black holes, recently detected by their gravitational wave signal, of stellar or primordial origin? Answering this question will have profound implications for our understanding of the Universe, including the nature of dark matter, the early Universe and stellar evolution. We build on the idea that the clustering properties of merging binary black holes can provide information about binary formation mechanisms and origin. The cross-correlation of galaxy with gravitational wave catalogues carries information about whether black hole mergers trace more closely the distribution of dark matter—indicative of primordial origin—or that of stars harboured in luminous and massive galaxies—indicative of a stellar origin. We forecast the detectability of such signal for several forthcoming and future gravitational wave interferometers and galaxy surveys, including, for the first time in such analyses, an accurate modelling for the different merger rates, lensing magnification and other general relativistic effects. Our results show that forthcoming experiments could allow us to test most of the parameter space of the still viable models investigated, and shed more light on the issue of binary black hole origin and evolution.

Cascaded systems analysis of shift‐variant image quality in slit‐scanning breast tomosynthesis

Digital breast tomosynthesis (DBT) is becoming an important part of breast cancer screening and diagnosis. Compared to two-dimensional mammography, tomosynthesis introduces limited three-dimensional (3D) resolution, but maintains high in-plane resolution, low dose, and allows for similar clinical protocols. The scanning motion and oblique projections of tomosynthesis acquisitions introduce shift-variance to the image quality, in addition to effects such as source blurring and geometric magnification. Shift-variant detector response caused by oblique incidence has been extensively studied previously and is most easily mitigated by letting the source and detector move in sync. In addition, conical reconstruction grids, that is, a grid aligned with the central tomosynthesis projection, have been proposed to compensate for magnification effects. This paper introduces a shift-variant cascaded systems model for tomosynthesis and validates it against measurements. As an example, the model was used to investigate the shift-variance of a tomosynthesis system. The shift-variant cascaded systems model was validated on a slit-scanning photon-counting DBT system, with synchronous source-detector movement, using simple back-projection in a conical reconstruction volume. The modulation transfer function (MTF), normalized noise-power spectrum (NNPS), and detective quantum efficiency (DQE) were used as figures of merit. Simulations were performed for single points while measurements were done over a finite volume, assuming local shift invariance. To investigate the full extent of shift-variance, 80 locations across the volume were simulated, and the MTF and DQE at 2.5lp/mm were calculated as a function of position. The simulated metrics generally agreed well with their corresponding measurements. The frequency at 50% MTF along the scan direction showed a relatively small variation, ranging from 2.1 to 2.4lp/mm for the different locations. The frequency at 50% MTF along the chest-mammilla direction showed a larger variation, ranging from 2.9 to 3.8lp/mm. All points exhibited a similarly shaped NNPS but the noise magnitude varied with slice height. The zero-frequency DQE in reconstructed slices was lower than that of the projections, an effect likely caused by noise-aliasing increasing the zero-frequency noise. A shift-variant cascaded systems model has been developed for slit-scanning tomosynthesis using simple back-projection. The model was successfully validated against measurements. Even though the study was performed on a slit-scanning system, several parts of the framework can be applied and extended to other tomosynthesis geometries. The conical reconstruction grid has low variation in image quality in the scan direction where the 3D information is acquired, but source and geometric magnification still dominate in the slit direction, causing a larger variation in image quality. We conclude that image quality is close to shift-invariant in the scan direction, but not in the height and chest-mammilla directions, and we recommend that small measurement volumes are used when measuring image quality in these directions to minimize the effects of shift variance.

Effect of gravitational lensing on the distribution of gravitational waves from distant binary black hole mergers

The detailed observation of the distribution of redshifts and chirp masses of binary black hole mergers is expected to provide a clue to their origin. In this paper, we develop a hybrid model of the probability distribution function of gravitational lensing magnification taking account of both strong and weak gravitational lensing, and use it to study the effect of gravitational lensing magnification on the distribution of gravitational waves from distant binary black hole mergers detected in ongoing and future gravitational wave observations. We find that the effect of gravitational lensing magnification is significant at high ends of observed chirp mass and redshift distributions. While a high mass tail in the observed chirp mass distribution is produced by highly magnified gravitational lensing events, we find that highly demagnified images of strong lensing events produce a high redshift ($z_{\rm obs}> 15$) tail in the observed redshift distribution, which can easily be observed in the third-generation gravitational wave observatories. Such a demagnified, apparently high redshift event is expected to be accompanied by a magnified image that is observed typically $10-100$ days before the demagnified image. For highly magnified events that produce apparently very high chirp masses, we expect pairs of events with similar magnifications with time delays typically less than a day. This work suggests the critical importance of gravitational lensing (de-)magnification on the interpretation of apparently very high mass or redshift gravitational wave events.

Interpreting Atom Probe Data from Oxide-Metal Interfaces.

Understanding oxide-metal interfaces is crucial to the advancement of materials and components for many industries, most notably for semiconductor devices and power generation. Atom probe tomography provides three-dimensional, atomic scale information about chemical composition, making it an excellent technique for interface analysis. However, difficulties arise when analyzing interfacial regions due to trajectory aberrations, such as local magnification, and reconstruction artifacts. Correlative microscopy and field simulation techniques have revealed that nonuniform evolution of the tip geometry, caused by heterogeneous field evaporation, is partly responsible for these artifacts. Here we attempt to understand these trajectory artifacts through a study of the local evaporation field conditions. With a better understanding of the local evaporation field, it may be possible to account for some of the local magnification effects during the reconstruction process, eliminating these artifacts before data analysis.

Probing cosmic velocity–density correlations with galaxy luminosity modulations

Abstract We study the possibility of using correlations between spatial modulations in the observed luminosity distribution of galaxies and the underlying density field as a cosmological probe. Considering redshift ranges, where magnification effects due to gravitational lensing may be neglected, we argue that the dipole part of such luminosity–density correlations traces the corresponding velocity–density signal which may thus be measured from a given galaxy redshift catalogue. Assuming an SDSS-like survey with mean density $\overline{n}=0.01 (h^{-1}$ Mpc)−3 and effective volume Veff = 0.2(h−1 Gpc)3 at a fiducial redshift $z$ = 0.1, we estimate that the velocity–density correlation function can be constrained with high signal-to-noise ratio ≳ 10 on scales 10–100 Mpc. Similar conclusions apply to the monopole which is sensitive to the environmental dependence of galaxy luminosities and relevant to models of galaxy formation.

Оптическая когерентная томография у пациентов с аномалиями рефракции. Сообщение 3: Толщина слоя ганглиозных клеток сетчатки

Purpose. Investigation of the influence of the axial length of the eye on the thickness of the ganglion cell-inner plexiform layer (GCIPL) and the development of methods for its evaluation in patients with myopia in the age of over 40 years. Material and methods . The study involved 53 patients (53 eyes) over the age of 40 years, with medium- and high-degree myopia, as well as 80 healthy subjects (80 eyes) of the same sex and age with emmetropia (control group). OCT was performed on a Cirrus HD-OCT device (Carl Zeiss Meditec). Results. To assess the influence of the optical magnification effect on the average thickness of the GCIPL, the authors and the programmer A.A. Evsukov created a computer program. The average thickness of the GCIPL in the control group was 79.0±5.3 (68-90) μm. In the group of patients with myopia, the GCIPL thickness was lower by an average of 5.1 μm (73.9±5.2, 64 to 86 μm, P<0.000). Correction by the computer program reduced this difference by less than ⅓, to 3.5 μm (75.5±5.3, 65 to 88μm, difference from the controls and from the initial data: P<0.000). Theoretical calculations showed a significant increase in the surface area of the myopic eye. A table and normative database have been developed for correctly estimating the thickness of the GCIPL based on the axial length of the eye. Conclusion. Thinning of GCIPL in patients with medium- and highdegree myopia is only partially associated with the effect of optical magnification, and is more due to the stretching of the posterior segment of the eyeball. An original technique for assessing the thickness of the GCIPL in patients with myopia, adapted to the Cirrus HD-OCT device, is proposed.

Stochastic response of structures with hybrid base isolation systems

In 2004, two R/C residential buildings were retrofitted by using a hybrid base isolation system in Solarino, Sicily, and subsequently five free vibration tests were carried out in one of these buildings. The hybrid base isolation system combined high damping rubber bearings with low friction sliders. In terms of numerical modeling, a single-degree-of-freedom system is developed here with a new five-parameter trilinear hysteretic model for the simulation of the high damping rubber bearing, coupled with a Coulomb friction model for the simulation of the low friction slider. Furthermore, a shear beam type, four-degree-of-freedom model is used to numerically simulate the superstructure. Next, experimentally obtained data from the five initial-displacement, free vibration tests were used for the calibration of this six-parameter model describing the base isolation system. Following up on the model development, the present study employs Monte-Carlo simulations in order to investigate the effect of the unavoidable variation in the values of the six-parameter mechanical model on the response of both the hybrid base isolation system and the superstructure comprising the Solarino building. The calibrated parameters values from all the experiments are used as mean values, while the standard deviation for each parameter is deduced from the identification tests employing best-fit optimization for each experiment separately. The results of the Monte-Carlo simulations show that variation in the material parameters of the base isolation system produce a nonstationary effect in the response, which can be traced by the time evolution of its mean and standard deviation as computed from the response at different time instants. In addition, there is a magnification effect, since the coefficient of variation of the response, for most of the parameters, is larger than the coefficient of variation in the parameter values. The high level of nonlinearity in the base isolation system, as observed in the amplitude of vibration brought about by large initial displacements, helps explain the previously mentioned effects.

Visually induced analgesia in a deep tissue experimental pain model: A randomised crossover experiment.

Visualizing one's own painful body part appears to have an effect on reported pain intensity. Furthermore, it seems that manipulating the size of the viewed image can determine the direction and extent of this phenomenon. When visual distortion has been applied to clinical populations, the analgesic effects have been in opposition to those observed in some experimental pain models. To help resolve this problem, we explored the effect of visualisation and magnification of the visual image on reported pain using a delayed onset muscle soreness (DOMS) pain model. We induced DOMS in the quadriceps of 20 healthy volunteers. Forty-eight hours later, participants performed a series of painful contractions of the DOMS-affected muscle under four randomised conditions: (1) Viewing the injured thigh; (2) Viewing the contralateral thigh; (3) Viewing a neutral object; and (4) Viewing the injured thigh through magnifying glasses. For each condition, participants rated their pain intensity during a series of painful contractions. We observed that direct visualisation of the injured thigh had no effect on pain intensity when compared to viewing the contralateral thigh or neutral object. However, magnification of the DOMS-affected leg during the performance of painful contractions caused participants to report more pain than when viewing the injured thigh normally. These results further demonstrate that the effect of visualisation varies between different pain conditions. These results may have implications for the integration of visual feedback into clinical practice. We present delayed onset muscle soreness as a model for exploring visually induced analgesia. Our findings suggest that this phenomenon is expressed differently in exogenous and endogenous experimental pain models. Further exploration may offer a potential pathway for the integration of visual analgesia into the management of clinical pain.

Two-dimensional simulation of eccentric photorefraction images for ametropes: factors influencing the measurement.

Eccentric photorefraction and Purkinje image tracking are used to estimate refractive state and eye position simultaneously. Beyond vision screening, they provide insight into typical and atypical visual development. Systematic analysis of the effect of refractive error and spectacles on photorefraction data is needed to gauge the accuracy and precision of the technique. Simulation of two-dimensional, double-pass eccentric photorefraction was performed (Zemax). The inward pass included appropriate light sources, lenses and a single surface pupil plane eye model to create an extended retinal image that served as the source for the outward pass. Refractive state, as computed from the luminance gradient in the image of the pupil captured by the model's camera, was evaluated for a range of refractive errors (-15D to +15D), pupil sizes (3mm to 7mm) and two sets of higher-order monochromatic aberrations. Instrument calibration was simulated using -8D to +8D trial lenses at the spectacle plane for: (1) vertex distances from 3mm to 23mm, (2) uncorrected and corrected hyperopic refractive errors of +4D and +7D, and (3) uncorrected and corrected astigmatism of 4D at four different axes. Empirical calibration of a commercial photorefractor was also compared with a wavefront aberrometer for human eyes. The pupil luminance gradient varied linearly with refractive state for defocus less than approximately 4D (5mm pupil). For larger errors, the gradient magnitude saturated and then reduced, leading to under-estimation of refractive state. Additional inaccuracy (up to 1D for 8D of defocus) resulted from spectacle magnification in the pupil image, which would reduce precision insituations where vertex distance is variable. The empirical calibration revealed a constant offset between the two clinical instruments. Computational modelling demonstrates the principles and limitations of photorefraction to help users avoid potential measurement errors. Factors that could cause clinically significant errors in photorefraction estimates include high refractive error, vertex distance and magnification effects of a spectacle lens, increased higher-order monochromatic aberrations, and changes in primary spherical aberration with accommodation. The impact of these errors increases with increasing defocus.

Magnification effect of Kerr metric by configurations of collisionless particles in non-isotropic kinetic equilibria

A test fluid composed of relativistic collisionless neutral particles in the background of Kerr metric is expected to generate non-isotropic equilibrium configurations in which the corresponding stress-energy tensor exhibits pressure and temperature anisotropies. This arises as a consequence of the constraints placed on single-particle dynamics by Killing tensor symmetries, leading to a peculiar non-Maxwellian functional form of the kinetic distribution function describing the continuum system. Based on this outcome, in this paper the generation of Kerr-like metric by collisionless N -body systems of neutral matter orbiting in the field of a rotating black hole is reported. The result is obtained in the framework of covariant kinetic theory by solving the Einstein equations in terms of an analytical perturbative treatment whereby the gravitational field is decomposed as a prescribed background metric tensor described by the Kerr solution plus a self-field correction. The latter one is generated by the uncharged fluid at equilibrium and satisfies the linearized Einstein equations having the non-isotropic stress-energy tensor as source term. It is shown that the resulting self-metric is again of Kerr type, providing a mechanism of magnification of the background metric tensor and its qualitative features.

Laparoscopic colorectal resection under the concept of membrane anatomy

Total mesorectal excision(TME)and complete mesoclic excision (CME)concepts make people aware of membrane integrity; the effect of endoscopic magnification and the hemostatic effect of ultrasonic scalpel, surgical field of view clearly, to further understand the structure of the membrane, which proposed the surgical anatomy of the membrane. This article describes the surgical membrane anatomy from the colorectal membrane of the embryonic development and membrane anatomical features that guide laparoscopic colorectal surgery. Key words: Colorectal surgery; Laparoscopes; Dissection; Mebrane

Magnifying the effective intrinsic stress of surface coating on the performance of nano-scaled Ge-based high-k/metal gate device through superficial layout designs

Scaling of dimensions for traditional Si-based metal oxide semiconductor field-effect transistors (MOSFETs) is limited. Thus, a promising transistor material and a corresponding fabricated process should be selected to improve the electrical performance of advanced nanodevices. According to the viewpoint of material survey, germanium-based MOSFET, which exhibits intrinsic high mobility, is considered a promising candidate for next-generation transistors. With the suitable introduction of stress-induced thin coating, such as silicon nitride contact etch stop layer (CESL), the electron mobility of devices can be further enhanced to compensate for the significant degeneration of lattice-mismatched stress resulting from rigorous dimensional shrinkage. The tensile CESL is commonly adopted to induce a biaxial tensile stress on the wide scope of n-type MOSFETs. However, the induced tensile stress that occurs along the transverse direction of a concerned device channel decreases the carrier mobility. Hence, this study proposes special layout designs with dummy gates placed on the transverse direction of the device channel. The effect of stress magnification from CESL coating on Ge-based n-type MOSFET is presented via a finite element analysis and a high-order piezoresistance model. Result shows that an enhanced carrier mobility gain of approximately 16.47% is obtained when a 50 nm-thick CESL with a tensile of 2.0 GPa is considered.

Effects of magnification and sampling resolution in X-ray computed tomography for the measurement of additively manufactured metal surfaces

Recent studies have shown that X-ray computed tomography (XCT) can be used to measure the surface topography of additively manufactured parts. However, further research is necessary to fully understand XCT measurement performance. Here, we show how magnification of the X-ray projections and resolution of the volumetric reconstruction grid influence the determination of surface topography in the XCT data processing pipeline. We also compare XCT results to coherence scanning interferometry (CSI) measurements and find that by increasing the magnification of the X-ray projections, smaller topographic detail can be resolved, approaching the lateral resolution of CSI. Results show that there is an optimum setting for magnification, below and above which XCT measurement performance can degrade. The resolution of the volumetric reconstruction grid has a less pronounced effect, but in general, adopting higher or lower resolutions than the default leads to degraded repeatability in surface determination. The problem of determining sensitivity of XCT surface measurement as a function of setup parameters is complex, and it is not yet possible to provide optimal setup configurations that work regardless of object geometry. However, the methods presented here, as well as the results obtained, represent a useful contribution to good practice for XCT measurement of surfaces.