Liquid mirrors

1995 ◽  
Vol 73 (3-4) ◽  
pp. 109-125 ◽  
Author(s):  
Ermanno F. Borra

The surface of a spinning liquid takes the shape of a paraboloid that can be used as a reflecting mirror. This very old and nearly forgotten concept has recently been revived and I review its present status. Extensive interferometric tests of liquid mirrors (the largest one having a diameter of 2.5 m) show excellent optical qualities. I discuss the factors that can limit the optical quality of liquid mirrors, how to minimize them as well as the basic technology. A handful of liquid mirrors have now been built that are used for scientific work. I show representative data obtained from 2.65 m diameter liquid mirror telescopes used for astronomy and the atmospheric sciences (LIDAR). Section 5, of particular interest to cosmologists or astronomers using surveys, examines the expected performance of 4 m liquid mirror telescopes (LMTs) dedicated to cosmological surveys. It is rather impressive, due to the fact that the instruments work full-time on 4 year surveys: Spectrophotometry reaches B = 24 for all objects within over 100 square degrees and wide-band photometry reaches about B = 28. I consider the future of liquid mirror telescopes: limits to their sizes, engineering issues, as well as speculations on lunar or space LMTs. I briefly mention the possibility of nonrotating GRIN (gradient index) liquid mirrors. Finally, I address the issues of the field accessible to LMTs equipped with novel optical correctors. Optical design work, and some exploratory laboratory work, indicate that a single LMT should be able to access, with excellent images, small regions anywhere inside fields as large as 45°.

1997 ◽  
Vol 109 ◽  
pp. 319 ◽  
Author(s):  
E. F. Borra ◽  
G. Tremblay ◽  
Y. Huot ◽  
J. Gauvin

2020 ◽  
pp. paper51-1-paper51-11
Author(s):  
Elena Zaeva-Burdonskaya ◽  
Daria Kardashenko

The article considers the potential of computer graphic modeling based on the experience of distance learning in design and art disciplines at the Department of Environmental design of the Stroganov Academy. An analysis of both practical and theoretical work of the Department during the semester made it possible to conclude that the model for the integration of full-time and distance learning, the individual and interactive approaches to the student is optimal for schools of creative arts. The experiment revealed the greatest flexibility and adaptability to the online format of the methodological material of the disciplines of graphic tools, its maximum openness to self-study, its role in innovative forms of design work, of the creative search for student’s own learning style.


2006 ◽  
Vol 969 ◽  
Author(s):  
Krishna C. Mandal ◽  
Sung H. Kang ◽  
Michael K. Choi

AbstractThe single crystal growth of layered semiconductors GaSe and GaTe by vertical Bridgman technique using zone refined selenium (Se), tellurium (Te) and high purity (HP) gallium (Ga) have been described. The grown crystals (2.5 cm diameter and ∼10 cm long) have demonstrated efficient broadband tunable THz emission and as sensitive THz detectors. The crystals have shown promising characteristics with good optical quality, high dark resistivity, wide band gap (GaSe-2.01 eV and GaTe-1.66 eV at 300 K), good anisotropic (parallel, p & perpendicular, pa) electrical properties (σ∥ vs σ⊥ and μ∥ vs σ⊥) and long term stability. Different steps involved in processing GaSe and GaTe crystals as THz sources and sensors are described.


2022 ◽  
Vol 134 (1031) ◽  
pp. 015004
Author(s):  
Yuji Ikeda ◽  
Sohei Kondo ◽  
Shogo Otsubo ◽  
Satoshi Hamano ◽  
Chikako Yasui ◽  
...  

Abstract WINERED is a novel near-infrared (NIR) high-resolution spectrograph (HRS) that pursues the highest possible sensitivity to realize high-precision spectroscopy in the NIR as in the optical wavelength range. WINERED covers 0.9–1.35 μm (z, Y, and J-bands) with three modes (Wide mode and two Hires modes) at the maximum spectral resolutions of R = 28,000 and R = 70,000. For fulfilling the objective, WINERED is designed with an unprecedentedly high instrument throughput (up to 50% at maximum including the quantum efficiency of the array) that is three times or more than other existing optical/NIR HRSs. This is mainly realized by a combination of non-white pupil and no fiber-fed configuration in optical design, the moderate (optimized) wavelength coverage, and the high-throughput gratings. Another prominent feature of WINERED is “warm” instrument despite for infrared (IR) observations. Such non-cryogenic (no cold stop) IR instrument finally became possible with the combination of custom-made thermal-cut filter of 10−8 class, 1.7 μm cutoff HAWAII-2RG array, and a cold baffle reducing the direct thermal radiation to the IR array into the solid angle of f/2. The thermal background is suppressed below 0.1 photons pixel−1 s−1 even in the wide band of 0.9–1.35 μm under the environment of 290 K. WINERED had been installed to the 3.58 m New Technology Telescope at La Silla Observatory, ESO, since 2017. Even with the intermediate size telescope, WINERED was confirmed to provide a limiting magnitude (for SNR = 30 with 8 hr. integration time) of J = 16.4 mag for the Wide mode and J = 15.1 mag for the Hires mode, respectively, under the natural seeing conditions. These sensitivities are comparable to those for the existing NIR-HRSs attached to the 8–10 m class telescopes with AO. WINERED type spectrographs may become a critical not only for the currently on-going extremely large telescopes to reduce the developing cost and time but also for smaller telescopes to extend their lives with long programs.


2013 ◽  
Vol 284-287 ◽  
pp. 2729-2734
Author(s):  
Min Wen Wang ◽  
Wei Chuang Lin ◽  
Ming Hsiao Lee

Neural network optimal optical design and Roll to Roll (R2R) microfabrication has been integrated in the development of a light guide film (LGF) for liquid crystal display application in this study. TracePro software was used for optical simulation work for the light guide film. Back-propagation neural network (BPNN) was applied to establish a light guide film optical quality predictor. Combined with genetic algorithms (GA), global optimization of the optical quality was achieved. The optimal pattern radii of different zones range from 40 μm to 210 μm were first transferred to an 80 μm thick stainless steel sheet through lithograpgy and etching process. The patterned sheet was then wrapped around the stainless steel roller for R2R fabrication of the patterns on a 188 μm thick PET substrate with UV resin. When operated with imprinting pressure of 0.61 MPa and substrate speed of 0.251 m/min, the LGF measurement results showed that the replication rate is around 98% while the luminace uniformity reaches 74.9%.


1997 ◽  
Vol 87 (6) ◽  
pp. 964-971 ◽  
Author(s):  
Samuel H. Greenblatt

✓ When Harvey Cushing announced his full-time commitment to neurological surgery in 1904, it was a discouraging and discouraged enterprise. Other surgeons' mortality rates for patients with brain tumors were 30 to 50%. By 1910 Cushing had operated on 180 tumors; he had a thriving practice, with a patient mortality rate of less than 13%. The three essential ingredients of his success were: 1) a new surgical conceptualization of intracranial pressure (ICP); 2) technical innovations for controlling ICP; and 3) establishment of a large referral base. In the years 1901 through 1905, the implications of his research on the “Cushing reflex” were quickly translated into surgical techniques for controlling ICP. In the period between 1906 and 1910, Cushing built up his referral practice by publishing widely, and especially by lecturing to medical audiences throughout the United States and Canada. His scientific work on ICP was essential to his clinical success, but without his professional and social ability to build a thriving practice, there would have been insufficient material for him to use to improve his approaches.


For many applications of time-domain spectroscopy it is desirable to improve the time resolution of electron-optical streak cameras to less than 200 fs in the u.v. visible and i.r. and to ca . 1 ps at X-ray wavelengths. A suite of interactive computer programs has been developed for electron-optical design, taking into account time dispersion. It is possible to analyse rapidly the details of both spatial and temporal imaging properties of currently available streak tubes and to optimize the designs for particular applications. The computed results are shown to be in excellent agreement with the experimental values for the Photochron II streak tube. The expected performance characteristics of a preliminary design for a new tube, the Photochron III, are given.


2000 ◽  
Author(s):  
Sylvie Robbe-Dubois ◽  
Pierre Antonelli ◽  
Udo Beckmann ◽  
Yves Bresson ◽  
Sandro Gennari ◽  
...  

2020 ◽  
pp. 42-47
Author(s):  
Polishchuk I.Ye.

Першорядною задачею освіти є формування мислення як самоцілі, що створює для особистості мож-ливості задля здійснення керованого впливу на соціальні явища та процеси, використовуючи сучасні знання та новітні технології. Здатність людини успішно соціалізуватися не можлива без інтелектуаліза-ції, яка має досягатися в освітньому процесі.Автором статті була розроблена анкета та проведене опитування магістрантів І року денної фор-ми навчання Херсонського державного університету (опитано 187 осіб, 44% від загальної чисельності в 2019–2020 навчальному році). Більшість здобувачів продовжує навчання за напрямом підготовки бака-лавріату. Однак опитування засвідчило, що основні теми дисципліни «Основи наукових досліджень» були засвоєні не досить глибоко з причини малої кількості аудиторних занять. Для багатьох магістрантів незрозумілим виявилося співвідношення філософських підходів, загальнонаукових та конкретно-нау-кових методів, а також зміст новітніх методологічних принципів та підходів. Більшість здобувачів не змогла відповісти на питання щодо наукових результатів, які вони отримували завдяки використанню зазначених ними методів. Це свідчить про недостатній зв’язок методології як теорії та наукової прак-тики. Було також виявлено, що більшість магістрантів не пов’язує майбутню професійну діяльність із науковими дослідженнями. Ця обставина зобов’язує викладачів посилити відповідальність за форму-вання гідного відношення здобувачів вищої освіти до науки як соціального і професійного інституту та теоретичного мислення як основи будь-якої високопрофесійної діяльності.Слід знайти оптимальне колегіальне рішення (у кожному університеті ексклюзивне) стосовно під-вищення в навчальних програмах різних напрямів освіти «питомої ваги» методологічного складника, а також сучасних форм підвищення методологічної підготовки викладачів теоретичних дисциплін. The primary task of education is the formation of thinking as an end in itself which creates opportunities for individuals to exert significant influence on social phenomena and processes using modern knowledge and the latest technologies. The ability of a person to successfully socialize is unthinkable without intellectualization which must be achieved in the educational process.The author of the article developed a questionnaire and conducted a survey of the first-year full-time postgraduates (master’s degrees) at Kherson State University (187 people were interviewed, which is 44% of the total amount in the 2019–2020 academic year). Most degree-seeking students continue their studies in the bachelor’s degree program. However, the survey showed that the main topics of the course “Fundamentals of Scientific Knowledge”, which was studied for bachelor’s degree programmes, are not sufficiently captured due to the small amount of class hours. For many postgraduates (master’s degrees) the relationship between the philosophical approaches themselves, general scientific and special scientific methods, as well as the content of the latest methodological principles, turned out to be incomprehensible. It is a matter of concern that many degree-seeking students were not able to answer the question about the results they obtained in scientific work through the use of the methods they specified. This indicates a lack of connection between methodological theory and scientific practice in the educational process. It was also found that the majority of postgraduates (master’s degrees) do not associate their future professional activities with scientific research. This circumstance obliges teachers to strengthen their responsibility for forming a decent attitude of degree-seeking students to science as a social and professional institution, as well as to theoretical thought as the basis of any highly professional activity.It is necessary to find an optimal collegial solution (exclusive at each university) to increase the “specific weight” of the methodological component in the curriculum documents of different branches of education, as well as regarding modern forms of improving the level of methodological competences of teachers of various theoretical disciplines.


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