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Weihong Song - One of the best experts on this subject based on the ideXlab platform.
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Experimental study on absolute measurement of spherical surfaces with Shift-Rotation method based on Zernike polynomials
Ninth International Symposium on Precision Engineering Measurement and Instrumentation, 2015Co-Authors: Weihong Song, Xi Hou, Hongwei JingAbstract:Absolute testing methods have been widely employed in the accurate metrology of optical surface deviation. As a general method, the Shift-Rotation method requires several Rotations and translations of the surface under test. And the surface deviation of the reference and the surface under test can be both calculated in terms of Zernike polynomials. The validity of the Shift and Rotation procedure was proved through experiments. Two different transmission spheres (with the same F number but different quality of the reference surfaces) were used to test the same spherical surface under test. The test results of the spherical surface under test are in good agreement.
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Absolute calibration for Fizeau interferometer with the global optimized Shift-Rotation method
Optics and Lasers in Engineering, 2014Co-Authors: Weihong Song, Xi Hou, Wenchuan Zhao, Li Shifang, Yongjian WanAbstract:We present an absolute calibration method for Fizeau interferometer with global optimized Shift-Rotation, which requires Rotational and translational measurements. With a data matching method to decrease the alignment error of Rotations and translations, the accuracy can be guaranteed. The global optimized Shift-Rotation method can obtain the surface deviation accurately of both the reference and test surfaces in terms of Zernike polynomials. Experiments have been implemented to verify the validity of the absolute calibration, and the results show that the reference surface deviation agrees well with the calibration result of conventional two-sphere method. Simulations were performed to evaluate the errors introduced by Rotations and translations. (C) 2013 Elsevier Ltd. All rights reserved.
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Absolute interferometric Shift-Rotation method with pixel-level spatial frequency resolution
Optics and Lasers in Engineering, 2014Co-Authors: Weihong Song, Xi Hou, Yongjian WanAbstract:Absolute interferometric testing method of Shift-Rotation in a Fizeau interferometer is effective in optical surface metrology with high accuracy and has been developed for decades. A pixel-level spatial frequency solution of interferometric Shift-Rotation method is presented in the manuscript. It requires a 90 degrees Rotational measurement and at least two translational measurements with different translations in the x and y directions besides a measurement at an original confocal position (0 degrees). With the well-organized absolute procedures, the absolute surface deviation of the test and reference surface can be obtained accurately with pixel-level spatial frequency resolution. As a result, the absolute results of the method contain much more mid-to high spatial frequency information and it is useful to directly detect the defects (dusts, pits) of the test and reference surfaces. No orthogonal polynomials fitting (such as Zernike polynomials) and interpolations are required in the calculation, and the absolute results can be guaranteed with high accuracy. Experimental absolute results of flat surfaces are given. (C) 2013 Elsevier Ltd. All rights reserved.
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Experimental Study on the Absolute Measurement of Flats
Fringe 2013, 2014Co-Authors: Wenchuan Zhao, Weihong SongAbstract:We present an absolute method of Shift-Rotation to calibrate the flatness of flats. Compared with the conventional three-flat test method, the method requires only two flat and no flips of the flats. And there will be no sag errors introduced by gravity deformations because of the flips of flats. The details of the method are given out in the paper. With multi-Rotational measurements and translation measurements, the surface deviation of flats can be obtained with the method. Experimental results are presented to show the availability of the absolute method.
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Absolute measurement of flats with the method of Shift-Rotation
Optical Review, 2013Co-Authors: Weihong Song, Xi Hou, Wenchuan Zhao, Yongjian WanAbstract:We present an absolute measurement of flats in a Fizeau interferometer with the method of Shift-Rotation, which only requires Rotational measurements and Shift measurement with a translation. Experiments have been carried out to verify the validity of the absolute testing method, and the results show that the reference surface deviation measured with the Shift-Rotation method agrees well with that of another calibration result with traditional three-flat absolute procedure; the root-mean-square (RMS) of the residual figure between them is ∼0.4 nm.
Bjørn Bjorvatn - One of the best experts on this subject based on the ideXlab platform.
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Pain complaints after consecutive nights and quick returns in Norwegian nurses working three-Shift Rotation: an observational study.
BMJ Open, 2020Co-Authors: Maria Katsifaraki, Mikko Härmä, Kristian Bernhard Nilsen, Jan Olav Christensen, Morten Wærsted, Stein Knardahl, Bjørn Bjorvatn, Dagfinn MatreAbstract:Objectives To determine whether nurses working consecutive night Shifts, or short transitions between Shifts (quick returns (QRs)), yielded higher risk for pain complaints when compared with regular morning Shifts. Sleep duration was tested as a potential mediator. Design Observational diary study. Setting Random hospitals. Participants Nurses with three-Shift Rotation (morning, evening and night), n=679, 22–63 years old. Outcomes measures Daily ratings of working hours, sleep and subjective pain complaints in six anatomical regions (head, neck/shoulder/upper back, upper extremity, low back, lower extremity and abdomen) for 28 days. In addition, we assessed demographics, habitual sleep and pain complaints, work and lifestyle factors. It was tested (1) whether the risk for pain complaints was higher after workday 3 versus after workday 2, and whether the difference was larger for consecutive night Shifts versus consecutive morning Shifts, and (2) whether the risk for pain complaints was higher after QRs versus after two morning Shifts. Risk for pain complaints refers to combined increased risk for any pain and risk for increased intensity. Results Adjusted analyses showed no Shift type by workday interaction for pain complaints in the neck/shoulder/upper back, upper extremities, low back, lower extremities or abdomen. For headache, a strong trend indicated that the risk was higher on workday 3 compared with workday 2 for night Shifts (OR 1.13, 95% CI 0.99 to 1.28). The risk was lowered if sleep duration was taken into account (OR 0.37, 95% CI 0.17 to 0.81). No conclusive support was found for the risk for pain complaints being higher after QRs, compared with after morning Shifts. Conclusions For five of six pain complaints, the hypotheses were not supported by the current data. For headache, we found potential support for a sleep-relieving effect on headache after working several nights in a row. Pain complaints were not instigated or exacerbated by an evening-to-morning transition between Shifts.
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Shift work schedule and night work load effects on body mass index a four year longitudinal study
Scandinavian Journal of Work Environment & Health, 2018Co-Authors: Hogne Vikanes Buchvold, Stale Pallesen, Siri Waage, Bjørn BjorvatnAbstract:Objectives The aim of this study was to investigate changes in body mass index (BMI) between different work schedules and different average number of yearly night Shifts over a four-year follow-up period. Methods A prospective study of Norwegian nurses (N=2965) with different work schedules was conducted: day only, two-Shift Rotation (day and evening Shifts), three-Shift Rotation (day, evening and night Shifts), night only, those who changed towards night Shifts, and those who changed away from schedules containing night Shifts. Paired student’s t-tests were used to evaluate within subgroup changes in BMI. Multiple linear regression analysis was used to evaluate between groups effects on BMI when adjusting for BMI at baseline, sex, age, marital status, children living at home, and years since graduation. The same regression model was used to evaluate the effect of average number of yearly night Shifts on BMI change. Results We found that night workers [mean difference (MD) 1.30 (95% CI 0.70–1.90)], two Shift workers [MD 0.48 (95% CI 0.20–0.75)], three Shift workers [MD 0.46 (95% CI 0.30–0.62)], and those who changed work schedule away from [MD 0.57 (95% CI 0.17–0.84)] or towards night work [MD 0.63 (95% CI 0.20–1.05)] all had significant BMI gain (P<0.01) during the follow-up period. However, day workers had a non-significant BMI gain. Using adjusted multiple linear regressions, we found that night workers had significantly larger BMI gain compared to day workers [B=0.89 (95% CI 0.06–1.72), P<0.05]. We did not find any significant association between average number of yearly night Shifts and BMI change using our multiple linear regression model. Conclusions After adjusting for possible confounders, we found that BMI increased significantly more among night workers compared to day workers.
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A Reliability and Validity Study of the Bergen Shift Work Sleep Questionnaire in Nurses Working Three-Shift Rotations
Chronobiology International, 2012Co-Authors: Elisabeth Flo, Bjørn Bjorvatn, Simon Folkard, Bente E. Moen, Janne Grønli, Inger Hilde Nordhus, Stale PallesenAbstract:The “Bergen Shift Work Sleep Questionnaire” (BSWSQ) was developed to systematically assess discrete sleep problems related to different work Shifts (day, evening, night Shifts) and rest days. In this study, we assessed the psychometric properties of the BSWSQ using a sample of 760 nurses, all working in a three-Shift Rotation schedule: day, evening, and night Shifts. BSWSQ measures insomnia symptoms using seven questions: >30-min sleep onset latency, >30-min wake after sleep onset, >30-min premature awakenings, nonrestorative sleep, being tired/sleepy at work, during free time on work days, and when not working/on vacation. Symptoms are assessed separately for each work Shift and rest days, as “never,” “rarely,” “sometimes,” “often,” “always,” or “not applicable.” We investigated the BSWSQ model fit, reliability (test-retest of a subsample, n = 234), and convergent and discriminant validity between the BSWSQ and Epworth Sleepiness Scale, Fatigue Questionnaire, and Hospital Anxiety Depression Scale. We als...
Yongjian Wan - One of the best experts on this subject based on the ideXlab platform.
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Absolute calibration for Fizeau interferometer with the global optimized Shift-Rotation method
Optics and Lasers in Engineering, 2014Co-Authors: Weihong Song, Xi Hou, Wenchuan Zhao, Li Shifang, Yongjian WanAbstract:We present an absolute calibration method for Fizeau interferometer with global optimized Shift-Rotation, which requires Rotational and translational measurements. With a data matching method to decrease the alignment error of Rotations and translations, the accuracy can be guaranteed. The global optimized Shift-Rotation method can obtain the surface deviation accurately of both the reference and test surfaces in terms of Zernike polynomials. Experiments have been implemented to verify the validity of the absolute calibration, and the results show that the reference surface deviation agrees well with the calibration result of conventional two-sphere method. Simulations were performed to evaluate the errors introduced by Rotations and translations. (C) 2013 Elsevier Ltd. All rights reserved.
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Absolute interferometric Shift-Rotation method with pixel-level spatial frequency resolution
Optics and Lasers in Engineering, 2014Co-Authors: Weihong Song, Xi Hou, Yongjian WanAbstract:Absolute interferometric testing method of Shift-Rotation in a Fizeau interferometer is effective in optical surface metrology with high accuracy and has been developed for decades. A pixel-level spatial frequency solution of interferometric Shift-Rotation method is presented in the manuscript. It requires a 90 degrees Rotational measurement and at least two translational measurements with different translations in the x and y directions besides a measurement at an original confocal position (0 degrees). With the well-organized absolute procedures, the absolute surface deviation of the test and reference surface can be obtained accurately with pixel-level spatial frequency resolution. As a result, the absolute results of the method contain much more mid-to high spatial frequency information and it is useful to directly detect the defects (dusts, pits) of the test and reference surfaces. No orthogonal polynomials fitting (such as Zernike polynomials) and interpolations are required in the calculation, and the absolute results can be guaranteed with high accuracy. Experimental absolute results of flat surfaces are given. (C) 2013 Elsevier Ltd. All rights reserved.
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Absolute measurement of flats with the method of Shift-Rotation
Optical Review, 2013Co-Authors: Weihong Song, Xi Hou, Wenchuan Zhao, Yongjian WanAbstract:We present an absolute measurement of flats in a Fizeau interferometer with the method of Shift-Rotation, which only requires Rotational measurements and Shift measurement with a translation. Experiments have been carried out to verify the validity of the absolute testing method, and the results show that the reference surface deviation measured with the Shift-Rotation method agrees well with that of another calibration result with traditional three-flat absolute procedure; the root-mean-square (RMS) of the residual figure between them is ∼0.4 nm.
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Optimized absolute testing method of Shift-Rotation
Applied Optics, 2013Co-Authors: Weihong Song, Xi Hou, Yongjian WanAbstract:The absolute testing method of Shift-Rotation that combines the traditional N-position method and Zernike polynomial fitting has been commonly employed in surface metrology. It preserves the high spatial frequency of the surface deviation with the N-position method to obtain the Rotationally asymmetric surface deviation, but it suffers the kNθ order angular terms errors missed by the N-position method when it calculates the Rotationally symmetric surface deviation with the Zernike Rotationally symmetric polynomial fitting method. An optimized absolute testing method of Shift-Rotation is presented in this paper. It considers the missing kNθ order errors when the equations of the Rotationally symmetric surface deviation are solved. As a result, it is more accurate than the traditional method. Experimental absolute results of spherical surfaces are given.
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Simple and rapid data-reduction method with pixel-level spatial frequency of Shift-Rotation method
Applied Optics, 2013Co-Authors: Weihong Song, Hou Xintong, Yongjian WanAbstract:Absolute testing methods are commonly employed in surface metrology to calibrate the reference surface deviation and obtain the absolute deviation of the surface under test. A simple and reliable data-reduction method of absolute Shift-Rotation method with Rotational and translational measurements is presented here, which relies on the decomposition of the surface deviation into Rotationally asymmetric and symmetric components. The Rotationally asymmetric surface deviation can be simply obtained by classical N-position averaging method. After that, the two-dimensional problem of estimating the other Rotationally symmetric surface deviation can be simplified to a one-dimensional problem, and it can be directly calculated out with pixel-level spatial frequency based on several measurements of different translations in one same direction. Since that no orthogonal polynomials fitting, such as Zernike polynomials, is required in the calculation, the data reduction of the method is simple and rapid. Experimental absolute results of spherical surfaces are given.
Simon Folkard - One of the best experts on this subject based on the ideXlab platform.
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A Reliability and Validity Study of the Bergen Shift Work Sleep Questionnaire in Nurses Working Three-Shift Rotations
Chronobiology International, 2012Co-Authors: Elisabeth Flo, Bjørn Bjorvatn, Simon Folkard, Bente E. Moen, Janne Grønli, Inger Hilde Nordhus, Stale PallesenAbstract:The “Bergen Shift Work Sleep Questionnaire” (BSWSQ) was developed to systematically assess discrete sleep problems related to different work Shifts (day, evening, night Shifts) and rest days. In this study, we assessed the psychometric properties of the BSWSQ using a sample of 760 nurses, all working in a three-Shift Rotation schedule: day, evening, and night Shifts. BSWSQ measures insomnia symptoms using seven questions: >30-min sleep onset latency, >30-min wake after sleep onset, >30-min premature awakenings, nonrestorative sleep, being tired/sleepy at work, during free time on work days, and when not working/on vacation. Symptoms are assessed separately for each work Shift and rest days, as “never,” “rarely,” “sometimes,” “often,” “always,” or “not applicable.” We investigated the BSWSQ model fit, reliability (test-retest of a subsample, n = 234), and convergent and discriminant validity between the BSWSQ and Epworth Sleepiness Scale, Fatigue Questionnaire, and Hospital Anxiety Depression Scale. We als...
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effects of direction of Rotation in continuous and discontinuous 8 hour Shift systems
Occupational and Environmental Medicine, 2000Co-Authors: Philip Tucker, Lawrence Smith, I A Macdonald, Simon FolkardAbstract:OBJECTIVES—Previous research has produced conflicting evidence on the relative merits of advancing and delaying Shift systems. The current study assessed the effects of the direction of Shift Rotation within 8 hour systems, upon a range of measures including sleep, on Shift alertness, physical health, and psychological wellbeing. METHODS—An abridged version of the standard Shiftwork index which included retrospective alertness ratings was completed by four groups of industrial Shiftworkers on relatively rapidly rotating 8 hour systems (n=611). Two groups worked continuous systems that were either advancing or delaying; the other two groups worked discontinuous systems that were either advancing or delaying. RESULTS—Few effects were found of direction of Rotation on chronic measures of health and wellbeing, even when the systems incorporated "quick returns" (a break of only 8 hours when changing from one Shift to another). This was despite the use of measures previously shown to be sensitive to the effects of a broad range of features of Shift systems. However, advancing continuous systems seemed to be associated with marginally steeper declines in alertness across the Shift (F (3,1080)=2.87, p<0.05). They were also associated with shorter sleeps between morning Shifts (F (1,404)=4.01, p<0.05), but longer sleeps between afternoons (F (1,424)=4.16, p<0.05). CONCLUSIONS—The absence of negative effects of advancing Shifts upon the chronic outcome measures accorded with previous evidence that advancing Shifts may not be as harmful as early research indicated. However, this interpretation is tempered by the possibility that difficult Shift systems self select those workers most able to cope with their deleterious effects. The presence of quick returns in advancing continuous systems seemed to impact upon some of the acute measures such as duration of sleep, although the associated effects on alertness seemed to be marginal. Keywords: Shift Rotation; health; alertness
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Maintaining safety and high performance on Shiftwork.
Applied Ergonomics, 1996Co-Authors: Timothy H. Monk, Simon Folkard, A. A. I. WedderburnAbstract:This review of the Shiftwork area focuses on aspects of safety and productivity. It discusses the situations in which Shiftworker performance is critical, the types of problem that can develop and the reasons why Shiftworker performance can be impaired. The review ends with a discussion of the various advantages and disadvantages of several Shift Rotation systems, and of other possible solutions to the problem.
Hon-fai Yau - One of the best experts on this subject based on the ideXlab platform.
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Optical demonstration of Shift-, Rotation- and limited size-invariant pattern recognition using a circular harmonic-synthetic discrimination function filter
Optical and Quantum Electronics, 1996Co-Authors: Hon-fai Yau, Yueh Ou Yang, Pei-wen ChenAbstract:Optical means of performing pattern recognition possessing Shift-, Rotation- and limited size-invariance is demonstrated. The experimental set-up is a standard Fourier transform correlator with a binary circular harmonic (CGH) filter. The filtering function of the filter is obtained by the synthetic discriminant functions (SDF) method. In the process of synthesizing the filtering function, circular harmonic functions are chosen as the basic functions. Both optical results and computer simulation results demonstrate that the filter is able to recognize the target in every Rotational orientation and in the relative size range of 1–1.82.
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Shift-, Rotation-, and limited-scale-invariant pattern recognition using synthetic discriminant functions
Visual Communications and Image Processing '95, 1995Co-Authors: Ouyang Yueh, Pen-wen Chen, Hon-fai YauAbstract:We propose here a simple way to synthesize a Shift, Rotation and limited size correlation filter, making use of the idea of synthetic discriminant functions (SDF). The SDF is synthesized by superimposing four 2nd order circular harmonics of a training reference pattern in 4 different sizes. Computer simulation experiments have shown that the filter is indeed Shift, fully Rotation and limited size invariant over a size range from 1 to 1.75. The invariant range can be increased if more training patterns are used.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
