Mirror Back Research Articles

Closed-Loop Pointing Feedback for Heliostats in Concentrating Solar Power

Abstract Concentrating solar power (CSP) facilities need to ensure alignment of all sun-tracking heliostats onto the sunlight receiver. A method is proposed to keep all heliostats in a CSP facility under closed-loop pointing control while also providing feedback on the detailed alignment of the segment mirrors of each heliostat. The method is based on the sunlight directed toward the receiver, and thus works under full operational conditions and without the need of secondary optical alignments. It is based on retroreflectors (“retros”) to simultaneously return samples of the sunlight reflected by each mirror back to that same mirror. It goes beyond previous efforts at using retros by placing them into the concentrated sunlight, instead of in its periphery. Quartz glass will be used for its heat tolerance, and reflectivity modulation for visibility is achieved by rotating the retros. The technology can be retrofitted into existing CSP facilities to improve operational efficiency, and it can be used to relax the stability requirements of heliostats, and thus their cost, in the planning of new ones.

Confronting Ecological Monstrosity

Confronting Ecological Monstrosity

Quality of defoamer enema combined with bellym assage on the colonic preparation in elderly patients with constipation

Objective To explore the role of defoamer enema combined with bellym assage on the colonic preparation in elderly patients with constipation. Methods One hundred patients were divided into two groups by random number table method, the experimental group and the control group with 50 cases each. Patients in the control group were told to drink polyethyleneglycolelectrolytesolution 3 000 ml. Patients in the experimental group were told to drink polyethyleneglycolelectrolytesolution 2 000 ml. After medicinepre paration, the patients of experimental group were given defoamer enema. After that, they were undertaken counterclockwise massage for10 mins, then massageing clockwise until defecation. Results 14 patients with oral catharsis drugs failed to give up check, 46 cases of intervention group and 40 cases of control group finally complete intestinal preparation and colonoscopy. Intervention group patients after bowel preparation before the incidence of abdominal distension, abdominal pain were 6.52% (3/46), 8.70%(4/46), lower than the control group 65.00% (26/40), 25.00% (10/40), the difference was statistically significant (χ2= 32.74, 4.17, P< 0.05). Percent of pass was 65.22%(30/46) for intestinal preparation intervention group, significantly higher than the control group 35.00% (14/40), the difference was statistically significant (χ2= 7.82, P< 0.05). Intervention group intestinal cleanliness ratings of Ottawa total score was 4.00 (4.00), which was lower than the control group7.00 (4.50), the difference was statistically significant (Z= 3.80, P< 0.05). Endoscopic check process, the intervention group arrived at the terminal ileum and mirror back time were 7.00 (3.00) and 9.00 (1.00) min, were less than 9.00(6.50) and 10.50 (3.00) min in the control group, the difference was statistically significant (Z= 2.09, 4.53, P< 0.05). Intervention group of colons polyps detection rate was 67.39% (31/46), higher than that of control group 30.00% (12/40), the difference was statistically significant (χ2= 11.97, P< 0.05). Conclusions The bowel preparation with defoamer enema will enhance the intestinal tract cleaness and the detection rate of polyps in elderly patients with constipation. Key words: Aged; Constipation; Retention enema; Colonoscopy; Colonic preparation

From the Back of the Mirror: "Quicksilver," Tinfoil, and the Shimmer of Sorcery in African-American Vernacular Magic

The esoteric pharmacopeia of Hoodoo or Conjure is replete with aesthetic elements intended to introduce shining, glittering, or reflective surfaces into ritual performance. Polished silver dimes, tinfoil cigarette papers, liquid mercury, and the silver shavings from the backs of mirrors (the latter three examples known colloquially as quicksilver in the vocabulary of Conjure) are all employed toward a wide array of pragmatic ends, from cursing an enemy, to winning at gambling, detecting hostile sorcery to keeping the law away from a bootlegging business. Through analysis of key examples drawn primarily from Harry M. Hyatt's Hoodoo, Conjuration, Witchcraft, and Rootwork, this article explores these aesthetic inclinations as they manifest in vernacular belief and ritual practice.

Topology optimization-based lightweight primary mirror design of a large-aperture space telescope.

For the large-aperture space telescope, the lightweight primary mirror design with a high-quality optical surface is a critical and challenging issue. This work presents a topology optimization-based design procedure for a lightweight primary mirror and a new mirror configuration of a large-aperture space telescope is obtained through the presented design procedure. Inspired by the topology optimization method considering cast constraints, an optimization model for the configuration design of the mirror back is proposed, through which the distribution and the heights of the stiffeners on the mirror back can be optimized simultaneously. For the purpose of minimizing the optical surface deviation due to self-weight and polishing pressure loadings, the objective function is selected as to maximize the mirror structural stiffness, which can be achieved by minimizing the structural compliance. The total mass of the primary mirror is assigned as the constraint. In the application example, results of the optimized design topology for two kinds of mass constraints are presented. Executing the design procedure for specific requirements and postprocessing the topology obtained of the structure, a new mirror configuration with tree-like stiffeners and a multiple-arch back in double directions is proposed. A verification model is constructed to evaluate the design results and the finite element method is used to calculate the displacement of the mirror surface. Then the RMS deviation can be obtained after fitting the deformed surface by Zernike polynomials. The proposed mirror is compared with two classical mirrors in the optical performance, and the comparison results demonstrate the superiority of the new mirror configuration.

Efficient photon extraction from a quantum dot in a broad-band planar cavity antenna

We analyse the extraction of photons emitted from single InAs quantum dots embedded in planar microcavities. The structures are designed to achieve broad-band operation and high-collection efficiency from a device requiring straightforward fabrication, even with electrical contacts. The designs consist of a quantum dot in a GaAs membrane with asymmetric top and bottom mirrors and a top-side solid immersion lens (SIL). Four separate cases are considered in our design: a GaAs membrane only (case 1), GaAs membrane with a glass SIL on top (case 2), a GaAs membrane with a glass SIL on top and a back mirror consisting of Au (case 3), a GaAs membrane with a glass SIL on top of a distribute Bragg reflector mirror and Au back mirror (case 4). Both finite difference time domain and analytical simulations are used to calculate the electric field, power density, and far-field radiation pattern. For optimized structures (case 4), we obtain significant extraction efficiencies (&amp;gt;50%) with modest Purcell enhancements (∼20%) and a large spectral full-width-half-maximum (&amp;gt;100 nm). The high-extraction efficiency, broad-band operation, and facile fabrication make the proposed structures promising for realistic quantum dot devices.

Экспериментальные исследования зеркальной антенны с облучателем обратного излучения трехсантиметрового диапазона во временной области с преобразованием в частотную область

Экспериментальные исследования зеркальной антенны с облучателем обратного излучения трехсантиметрового диапазона во временной области с преобразованием в частотную область

Compensation of dynamic thermal deformations of mirrors in high-power slab lasers

A system of compensation of thermal deformations of resonator mirrors in high-power CO2 slab lasers based on profiled heating of the mirror back surface is studied theoretically and experimentally. It is shown that such a heating of a resonator mirror makes it possible to minimise dynamic distortions of the output-beam wave front in the case when the lasing power can be varied.

Boundary of the adiabatic motion of a charged particle in a dipole magnetic field

The motion of a charged particle in a dipole magnetic field is considered using a quasi-adiabatic model in which the particle guiding center trajectory is approximated by the central trajectory, i.e., a trajectory that passes through the center of the dipole. A study is made of the breakdown of adiabaticity in the particle motion as the adiabaticity parameter χ (the ratio of the Larmor radius to the radius of the magnetic field line curvature in the equatorial plane) increases. Initially, for χ≳0.01, the magnetic moment μ of a charged particle undergoes reversible fluctuations, which can be eliminated by subtracting the particle drift velocity. For χ≳0.1, the magnetic moment μ undergoes irreversible fluctuations, which grow exponentially with χ. Numerical integration of the equations of motion shows that, during the motion of a particle from the equatorial plane to the mirror point and back to the equator in a coordinate system related to the central trajectory, the analogue of the magnetic moment μ is conserved. In the equatorial plane, this analogue undergoes a jump. The long-term particle dynamics is described in a discrete manner, by approximating the Poincare mapping. The existence of the regions of steady and stochastic particle motion is established, and the boundary between these regions is determined. The position of this boundary depends not only on the adiabaticity parameter χ but also on the pitch angle. The calculated boundary is found to agree well with that obtained previously by using the model of a resonant interaction between particle oscillations associated with different degrees of freedom.

Three-dimensional displacement measurement using a newly designed moire´ interferometer

A new moireinterferometer for determining 3-D displacement field of a slightly strained body is proposed. In this interferometer, the specimen grating not only diffracts the incoming beam into several beams but also rediffracts the diffracted beams, each of them is reflected from a mirror back to the path of the incoming beam. The rediffracted beams are then directed to a camera to generate three interference pat- terns, which are sufficient to determine the 3-D displacement field. The governing equations corresponding to these interference patterns are derived, and the advantages of using this interferometer are described. Some experiments were carried out to verify the governing equations and advantages. © 2001 Society of Photo-Optical Instrumentation Engineers.

Life lessons and a loving epistemology: A response to Julie Laible?s loving epistemology

In this article, Colleen Capper identifies five lessons or gifts from Julie Laible's workand research: lessons about belief and faith, lessons about our academic work, lessons about our work and faith, lessons about time, and lessons about epistemology. Capper extends the three contours of Laible's loving epistemology by first suggesting that rather than trying to squelch problems in research, we need to conduct research that is openly problematic. Second, Capper extends Collins's three research criteria by suggesting the following. (1) Does your social theory mirror back to people their reality of their lives at a particular point in time? (2) Does this social theory equip people to name their own pain and oppression for themselves, how they harm themselves, how they harm others, how they experience forgiveness of themselves and others and how they experience forgiveness from others? (3) Does this social theory move people to question themselves and others, not to be critical, but to seek to understand? Does this social theory move people not only to struggle but also to experience joy, freedom, and happiness? Third, Capper agrees traveling to other worlds is important, but those travels need to include the worlds of those who with or without intention seek to hurt us in direct or indirect ways, and the worlds within ourselves.

Study of degradation mechanisms of a paint coating during an artificial aging test

The degradation of a paint coating applied to the backs of mirrors was studied using infrared spectroscopy during a standard test. This analytical tool showed that the protective coating is subject to alterations within a thickness ranging from the surface to at least 7.65μm. The effects of the normalized test lead to the dissolution of the calcium carbonate extenders and to chemical modifications of the paint binder. These phenomena are responsible for the progressive erosion of the paint coating surface and for a weakening of its protective properties. The paint film's degradation lead to random corrosion of the metallic layers that make up the mirror backs. ©

Under-reporting of trauma from lorry mirrors?

This note describes two recent cases of trauma from lorry mirrors protuding from the vehicles; its author considers it very likely that this is not an uncommon event. Details of the two cases are presented briefly, and the author knows of two other cases. Specifications of lorry mirrors in the UK are currently regulated within a European Economic Community Commission (EEC) Directive, dated 18 February 1985. The author considers that trauma from lorry mirrors, though perhaps unusual, could be under-reported. He suggests that: (1) the backs of mirrors should be of lighter colour, to become more visible; (2) the mirror should be made of a material less likely to cause injury on impact; (3) the mirror pivoting device should be checked at the MOT test; (4) the Department of Transport should be considering a review of its regulations to improve pedestrian safety.

High repetition rate figure eight laser with extracavity feedback

The operation of an erbium figure eight all-fibre laser with a fundamental repetition rate of 28.5 MHz is reported. The feedback of light rejected by the nonlinear amplifying loop mirror back into the laser is found to stabilise mode locking enhance startup, shorten the pulse lenght to 275fs, and provide a simple means of multiplying the repetition rate.

Social responding to mirrors in rhesus monkeys (Macaca mulatta): Effects of temporary mirror removal.

As a result of a long-term, longitudinal project initiated in 1978, a pair of rhesus macaques (Macaca mulatta) housed together in front of a mirror all their lives now exhibit relatively little interest in their reflection. Previous work has shown, however, that simply moving the mirror to a new location produces a short-term reinstatement of social responding to their images. As an extension of these findings, in this study the mirror was left in the same position but turned away from the cage. On turning the mirror back to face the cage 5 days later, both animals reacted as if confronted with another pair of monkeys and directed a burst of social responses at the mirror.

Transverse mode control in high gain, millimeter bore, waveguide lasers

A technique is presented for assuring TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</inf> transverse mode operation in visible wavelength lasers with bore diameters of 0.1- 1.0 mm. This then is a solution to the problem of obtaining TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</inf> mode output from pulse pumped dye lasers which have high and non-uniform gain. The desired mode control is achieved by confining the lasing medium in a waveguide and placing each resonator mirror so that its focal plane, rather than its center of curvature, lies at the nearest waveguide opening. Thus, the far-field pattern of the field distribution emerging from the waveguide opening is focused by the mirror back into the waveguide. For the proper choice of mirror curvature, the width of the central lobe of the far-field pattern is such that over 99 percent of the energy couples into the two lowest order modes of the waveguide. The waveguide transmits this bell-shaped field distribution to the opposite end where the process of propagating to the mirror and being reimaged is repeated. The end result is that a pulsed, laser pumped, waveguide dye laser has been made to produce a mode of the same quality as a TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</inf> mode, CW, HeNe laser. This technique has also improved the output mode distribution of flashlamp pumped dye lasers. Analysis of the resonator shows that a TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</inf> mode having a curved wavefront at the waveguide opening couples primarily to both the EH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> and EH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> waveguide modes. The amplitudes of the EH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> and EH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> modes, however, have a complex phase difference which results in a refocusing of the field distribution when both propagate in a hollow waveguide. The refocusing is shown to be a periodic function of the length of the waveguide. In addition, it is shown that as a result of gain or propagation loss differences for the two waveguide modes, the phase radius of curvature of the TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</inf> mode of a waveguide resonator does not in general match the mirror curvatures. This model of TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</inf> mode coupling to the EH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> plus EH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> modes results in a clearer physical insight into the interaction between the waveguide and free space portions of the resonator.

Nasal spirometry; a volumetric study of nasal air flow capacity.

THE simple and accurate method for the evaluation of nasal airway capacity has been widely searched for since Zwaardemaker first wrote about his cold mirror back in 1889.1Most of these attempts have been to make measurements of pressure changes either in the postnasal space or in a nasal mask during spontaneous respiration or during forced air flow either into or back from the nose.2-7 The method most in use today was originally presented by Lehmann in 1939, and further developed by Aschan et al, Craig, Solomon et al, Cass and Ogura. A transducer is used to measure the difference in pressure between the nasopharynx and a nasal mask and the actual amount of air flow is measured during spontaneous respiration using a pneumotachometer. These two values are plotted opposite each other on an oscilloscope screen and the line obtained has a slope which is representative of the

Incised Slate Disks from the Atlantic Watershed of Costa Rica

AbstractSlate backs of iron-pyrite mirrors have been found in the southwestern United States, Mexico, Guatemala, Costa Rica, Panama, Ecuador, and Peru. Three engraved slate disks were recently excavated at two sites in Costa Rica, one at La Fortuna and two at Guácimo. Slate disks in this region are not unusual. Many have traces of the gum that was used for glue, and at least one fragment bears traces of the wooden frame. The significance of these three plaques lies in the designs they bear. These designs indicate that the disks were made betweenA.D.435 and 500 in an area remote from lower Central America. Grave objects associated with the mirror backs include reworked jades; gold objects in Coclé, Quimbaya, and Guayas styles; and Incised Zoned Bichrome and Negative Painted Bichrome Incised wares. These disks and the objects associated with them provide insight into pre-Columbian interchange and trade routes in lower Central America, and they suggest that slate disks were important in commerce and perhaps served as ceremonial objects.