Actual Mirror Research Articles

Application of Numerical and Experimental Techniques for the Aero-Acoustic Characterisation of a Car Rear-View Mirror

Numerical as well as experimental approaches are used to capture aero-acoustic characteristics of a car rear-view mirror. The numerical study splits up into several parts. Using an actual production mirror, particular emphasis must be put on the geometry preparation and mesh generation. Initially, a CFD simulation of the entire car aerodynamics is performed to extract the proper flow boundary conditions for the aero-acoustic simulation of a smaller section surrounding the mirror. Pressure fluctuations on the surfaces extracted during an LES generate the data base required for the aeroacoustic post-processing. The acoustic pressure at several monitoring points is then calculated using Lighthill's Acoustic Analogy. To include refraction effects of the nearby surfaces a direct BEM approach is also employed. Utilizing the PIV method, local areas of increased turbulence are identified experimentally. Microphone measurements with and without the exterior mirror are performed.

Shape difference visualization for ancient bronze mirrors through 3D range images

AbstractJapanese archaeologists have paid special attention to ancient Chinese bronze mirrors because the mirrors may provide a key for the exact location of Yamatai State, which is one of the major archaeological controversies. Currently, archaeologists visually analyse ancient Chinese bronze mirrors for their shape difference. The practice requires a huge amount of time and effort. In this paper, we propose an automatic method for detecting the shape difference between a pair of ancient mirrors. The 3D data of the mirrors are obtained using a laser range scanner. Our algorithm then aligns them into the same coordinate and visualizes their shape differences. Our proposed algorithm provides fast and non‐damaging analysis for shape difference. Further analysis can be evaluated on our data instead of the actual mirror, so it can be performed by more than one group of archaeologists. Copyright © 2003 John Wiley & Sons, Ltd.

Mirror Tracing and the Provocation of Vascular-Dominant Reaction Pattern Through Heightened Attention

Abstract After a hint from Lang et al.'s (1997) defence cascade, researchers considered cognitive process experienced when encountering mental stress to be composed of four elements: (serially) first attention (Attent), second unpleasant affect (UnplAff) and sometimes pleasant affect (PlAff), and third cognitive coping (CogCop). The present study investigates the effect of each cognitive element on the provocation of the well-known vascular-dominant reaction pattern during mirror tracing: elevation of mean blood pressure mainly because of increases in total peripheral resistance. Twenty-four male students first underwent four computer-simulated mirror-tracing practices of 3 min each, then a 7 min adaptation followed by a 3 min baseline, and further four kinds of actual mirror tracing trials (Attent, UnplAff, PlAff, and CogCop) of 3 min each. Results on the cardiovascular measures indicated that every mirror-tracing trial indisputably provoked the vascular-dominant reaction pattern. An alpha-adrenergic vascular sympathetic activation was heightened. Self-report measures on the four cognitive elements suggested that heightened Attent seemed to contribute to provoking the reaction pattern. Although the UnplAff and PlAff trials had an active coping feature in a narrow sense, they could not provoke the cardiac-dominant reaction pattern. Differences in task difficulty among the mirror tracings could not explain the results. The implications of these results are discussed in order to better understand cardiovascular hemodynamics during mental stress.

Hypnotic mirrors and phantom pain: a single case study

AbstractUsing hypnosis, two main approaches to modifying phantom limb pain experience can be identified: ipsative imagery, which makes use of the patient's own imaginative interpretation of how the pain is generated, and a simulated movement approach. The latter approach shares many similarities with the ‘mirror’ technique recently advocated and used by Ramachandran (in non‐hypnotic settings) to create the experience of movement and in some (but not all cases) relief from pain in patients with a phantom limb. In this case study, we report the use of a hypnotically induced ‘virtual’ mirror experience that modified long standing intractable phantom limb pain despite generating a qualitatively inferior experience of movement in the phantom limb compared to that produced with an actual mirror. These preliminary findings suggest that the use of hypnotic movement imagery for the management of phantom limb pain is worth further investigation both in terms of its comparative ease of use and because of its potential for informing discussion as to the possible neurocognitive mechanisms involved. Copyright © 2002 British Society of Experimental and Clinical Hypnosis

Simulating electrostrictive deformable mirrors: I. Nonlinear static analysis

An electromechanical model of a deformable mirror was developed as a design tool for adaptive optical systems. The model consisted of a continuous, mirrored face sheet driven with multilayered, electrostrictive actuators. A fully coupled constitutive law simulated the nonlinear, electromechanical behavior of the actuators, while finite element computations determined the mirror's mechanical stiffness observed by the array. Static analysis of the mirror/actuator system related different electrical inputs to the array with the deformation of the mirrored surface. The model also examined the nonlinear influence of internal stresses on the active array's electromechanical performance and quantified crosstalk between neighboring elements. The numerical predictions of the static model agreed well with experimental measurements made on an actual mirror system. The model was also used to simulate the systems level performance of a deformable mirror correcting a thermally bloomed laser beam. The nonlinear analysis determined the commanded actuator voltages required for the phase compensation, and the resulting wavefront error.

Design and Implementation of a Robust Controller for a Free Gyro-Stabilized Mirror System

In this paper, we consider the problem of designing a robust controller for a multivariable servomechanism of a free gyro-stabilized mirror system where there exists cross-coupling between the axes. The nonlinear dynamics of the system are first linearized and reformulated into an H∞ problem. A reduced order output feedback controller is then designed using the asymptotic time-scale and eigenstructure assignment (ATEA) technique. The overall design has been implemented using a personal computer with C++ and tested on the actual gyro-stabilized mirror system. Our simulation and implementation results show that the design is very successful.

Mirror jitter: an overview of theoretical and experimental work

Mirror jitter is a flow-induced vibration phenomenon typical of convectively cooled optics. Flow separation points within the coolant supply lines, mirror manifolding, and mirror coolant passages produce internal turbulent pressure distributions, which lead to unbalanced fluctuating forces and resultant mirror jitter. The author reviews the known causes of jitter, methods to determine jitter forces as well as actual mirror jitter, and methods to measure jitter forces. A summary of known jitter force measurements is given, and an extensive bibliography of relevant literature is listed. Guidelines for evaluating system jitter and avoiding pitfalls are offered.

Improvement of beam divergence in pseudoparaboloidal bending of an x-ray mirror

The surface of a flat-plate quartz mirror has been investigated by bending it into a pseudoparaboloid with the mirror bender in BL-3A. The evaluation of the beam collimation and actual mirror curvature have been made by x-ray diffraction using the (+,−,−) arrangement of Si(111) crystals. The FWHM in (+,−,−) rocking curves of a whole beam was reduced from 42.7 to 14.1 arcsec with the collimating mirror. The distances deviating from the ideal paraboloid were found to be very small, i.e., less than 0.6 and 3.5 μm in ±200 and ±400 mm in the mirror length, respectively. The efficiency of the mirror was also estimated from the CeO2 diffraction patterns which were slightly but significantly improved in FWHM and peak intensity with the collimation.

Oe no Masafusa and the Spirit of Michizane

T ODAY, Tenjin RT worship flourishes as a Shinto cult dedicated to the spirit of Sugawara no Michizane 1 845-903, in his day Japan's most distinguished man of letters. In recognition of his talents, he was promoted to high office, only to be slandered by political rivals and exiled to Kyushu as the nominal Supernumerary Governor General of Dazaifu.1 There he was treated as a criminal and died a failure in his mortal career. His posthumous career, however, proved more successful. Fear of his angry ghost led to his pardon, promotion, and eventually, in the mid-tenth century, his apotheosis as Tenjin, 'the heavenly deity'. Japan had other and older heavenly deities, but none enjoyed the lasting popularity of this one. As the years passed, Tenjin worship proved to be a marvelously adaptablc faith. Perhaps its most consistent feature has been its enduring ability to capture the imagination and devotion of people with highly diverse interests. In metaphorical terms, it was, and still is, rather like a mirror, a favored metaphor among historians in both China and Japan. For them, historical writings were idealized mirrors that accurately reflected events of the past. Tenjin worship, in contrast, seems more like an actual mirror used most often to reflect the viewer's own image. Since religion is in the realm of the spiritual rather than the physical, the mirror of Tenjin does not reflect literal images. Instead, it reveals the dreams, or occasionally nightmares, of those who gaze into it. Founders of Tenjin worship, for example, included Michizane's descendants and their disciples who had maintained the family's tradition by becoming academicians and in Tenjin saw an epitome of learning whose great achievements they sought to emulate. The progeny of Michizane's formei

表面粗さＳＴＭ

To take a detailed characteristics of a surface topography for X-ray or laser mirrors, STMs (Scanning Tunneling Microscopes) have been found to be very useful, owing to their ultra-high spatial resolution. However, conventional STMs are not sufficiently useful for this industrial purpose, because of the small measurement area involved. The authors developed a Wide Range STM using monolithic mechanisms and have developed a wider range and easy to use STM. In this new instrument, a sample is scanned in lateral directions with divided electrodes bimorph PZTs. This furnishes the ability to achieve 200 μm×63 μm scan range and that an actual mirror, such as one which has a 50 mm diameter, can be set on the sample stage. It is possible to successfully measure a grating, whose pitch is 0.42 μm over about 200 μm scan line. Also, a diamond turning mirror was measured over an about 45 μm×2.5 μm area tentatively. The resolution for this one is 4 nm vertically, at the most. These measurements reveal the saw wave topography of the grating and considerable detail on diamond turning marks on the mirror surface. The proposed new STM is very useful, because this measurement gives more information, exceeding the amount available using contact stylus methods and optical methods.

Diamagnetic stability limit for a hot particle annulus in a plasma

The stability of a hot particle annulus in a mirror cell at arbitrary drift reversal is analyzed by using a cylindrical model with embedded currents that simulate the role of field line curvature in actual mirror experiments. New effects are included by taking into account the Landau damping arising from the spread of hot particle drift velocities. It is found that the ‘‘precessional layer’’ mode is destabilized near the pressure gradient value at which drift reversal is achieved. Its growth rate is proportional to N−4, where N−2 is a coupling constant γ2MHD/ ω̃2κ [ω̃κ is the curvature frequency, γMHD is the typical magnetohydrodynamic (MHD) growth rate]. In addition the unstable interaction of the precessional layer mode with surface waves that can propagate below and above the ion-cyclotron frequency is described. Below the ion-cyclotron frequency the surface wave resembles the Alfvén wave, while above the ion-cyclotron frequency the surface wave resembles a whistler wave.

An investigation of student understanding of the real image formed by a converging lens or concave mirror

Student understanding of the real images produced by converging lenses and concave mirrors was investigated both before and after instruction in geometrical optics. The primary data were gathered through interviews in which undergraduates taking introductory physics were asked to perform a set of prescribed tasks based on a simple demonstration. The criterion used to assess understanding was the ability to apply appropriate concepts and principles, including ray diagrams, to predict and explain image formation by an actual lens or mirror. Performance on the tasks, especially by students who had not had college instruction in geometrical optics, suggested the presence of certain naive conceptions. Students who had just completed the study of geometrical optics in their physics courses were frequently unable to relate the concepts, principles, and ray-tracing techniques that had been taught in class to an actual physical system consisting of an object, a lens or a mirror, and a screen. Many students did not seem to understand the function of the lens, mirror, or screen, nor the uniqueness of the relationship among the components of the optical system. Difficulties in drawing and interpreting ray diagrams indicated inadequate understanding of the concept of a light ray and its graphical representation.

Mirror fields for tower-type solar power plants

To obtain, in a receiver C, a point image of parallel rays tilted at an angle ψ with respect to the normal at the mirror centre S, the mirror surface must be a portion of a paraboloid having its focus in C, and its axis directed towards the sun and passing through S. Since this paraboloid will change with the sun's position, such a mirror is impossible. In this paper, it is suggested that the various paraboloid sectors should be replaced by double-curvature mirrors, driven in such a way as to maintain the minimum mirror curvature in the sun-mirror-receiver plane. The results thus obtained are compared with those obtained using a spherical mirror. Finally, the procedure used to determine the actual mirror field for a receiver, when the diameter of the aperture, the height, and the inclination of the axis are given, is reported.