Application of Sharafutdinov's Ray Transform in Integrated Photoelasticity

We explain the main concepts centered around Sharafutdinov's ray transform, its kernel, and the extent to which it can be inverted. It is shown how the ray transform emerges naturally in any attempt to reconstruct optical and stress tensors within a photoelastic medium from measurements on the state of polarization of light beams passing through the strained medium. The problem of reconstruction of stress tensors is crucially related to the fact that the ray transform has a nontrivial kernel; the latter is described by a theorem for which we provide a new proof which is simpler and shorter as in Sharafutdinov's original work, as we limit our scope to tensors which are relevant to Photoelasticity. We explain how the kernel of the ray transform is related to the decomposition of tensor fields into longitudinal and transverse components. The merits of the ray transform as a tool for tensor reconstruction are studied by walking through an explicit example of reconstructing the $\sigma_{33}$-component of the stress tensor in a cylindrical photoelastic specimen. In order to make the paper self-contained we provide a derivation of the basic equations of Integrated Photoelasticity which describe how the presence of stress within a photoelastic medium influences the passage of polarized light through the material

Full-field pulsed magneto-photoelasticity – Experimental Implementation

This paper contains a description of the experimental procedure employed when using a pulsed-magneto-polariscope (PMP) and some initial full-field through-thickness measurements of the stress distribution present in samples containing 3D stresses. The instrument uses the theory of magneto-photoelasticity (MPE), which is an experimental stress analysis technique that involves the application of a magnetic field to a birefringent model within a polariscope. MPE was developed for through-thickness stress measurement where the integrated through-thickness birefringent measurement disguises the actual stress distribution. MPE is mainly used in toughened glass where the through-thickness distribution can reduce its overall strength and so its determination is important. To date MPE has been a single-point 2D through-thickness measurement and the analysis time is prohibitive for the investigation of an area which may contain high localised stresses. The pulsed-magneto-polariscope (PMP) has been designed to enable the application of full-field 3D MPE [ ]. Using a proof-of concept PMP several experimental measurements were made, these were promising and demonstrate the potential of the new instrument. Further development of this technique presents several exciting possibilities including a tool for the measurement of the distribution of principal stress difference seen in a general 3D model

Improvement of Fourier Polarimetry for applications in tomographic photoelasticity

The use of the Fourier Polarimetry method has been demonstrated to extract the three characteristic parameters in integrated photoelasticity. In contrast to the phase-stepping method, it has been shown that the Fourier method is more accurate. However, the Fourier method isn't very efficient as it requires that a minimum of nine intensity images be collected during a whole revolution of a polarizer while the phase-stepping method only needs six intensity images. In this paper the Fourier transformation is used to derive the expression for determination of the characteristic parameters. Four Fourier coefficients are clearly identified to calculate the three characteristic parameters. It is found that the angular rotation ratio could be set arbitrarily. The angular rotation ratio is optimized to satisfy the requirements of efficiency and proper data accuracy, which results in data collection about three times faster than the methods suggested by previous researchers. When comparing their performance in terms of efficiency and accuracy, the simulated and experimental results show that these angular rotation ratios have the same accuracy but the optimized angular rotation ratio is significantly faster. The sensitivity to noise is also investigated and further improvement of accuracy is suggested

Distinction between clouds and ice/snow covered surfaces in the identification of cloud-free observations using SCIAMACHY PMDs

SCIAMACHY on ENVISAT allows measurement of different trace gases including those most abundant in the troposphere (e.g. CO₂, NO₂, CH₄, BrO, SO₂). However, clouds in the observed scenes can severely hinder the observation of tropospheric gases. Several cloud detection algorithms have been developed for GOME on ERS-2 which can be applied to SCIAMACHY. The GOME cloud algorithms, however, suffer from the inadequacy of not being able to distinguish between clouds and ice/snow covered surfaces because GOME only covers the UV, VIS and part of the NIR wavelength range (240-790 nm). As a result these areas are always flagged as clouded, and therefore often not used. Here a method is presented which uses the SCIAMACHY measurements in the wavelength range between 450 nm and 1.6 µm to make a distinction between clouds and ice/snow covered surfaces. The algorithm is developed using collocated MODIS observations. The algorithm presented here is specifically developed to identify cloud-free SCIAMACHY observations. The SCIAMACHY Polarisation Measurement Devices (PMDs) are used for this purpose because they provide higher spatial resolution compared to the main spectrometer measurements

Determination of the characteristic directions of lossless linear optical elements

We show that the problem of finding the primary and secondary characteristic directions of a linear lossless optical element can be reformulated in terms of an eigenvalue problem related to the unimodular factor of the transfer matrix of the optical device. This formulation makes any actual computation of the characteristic directions amenable to pre-implemented numerical routines, thereby facilitating the decomposition of the transfer matrix into equivalent linear retarders and rotators according to the related Poincare equivalence theorem. The method is expected to be useful whenever the inverse problem of reconstruction of the internal state of a transparent medium from optical data obtained by tomographical methods is an issue.Comment: Replaced with extended version as published in JM

Water vapour total columns from SCIAMACHY spectra in the 2.36 μm window

The potential of the shortwave infrared channel of the atmospheric spectrometer SCIAMACHY on Envisat to provide accurate measurements of total atmospheric water vapour columns is explored. It is shown that good quality results can be obtained for cloud free scenes above the continents using the Iterative Maximum Likelihood Method. In addition to the standard cloud filter employed in this method, further cloud screening is obtained by comparing simultaneously retrieved methane columns with values expected from models. A novel method is used to correct for the scattering effects introduced in the spectra by the ice layer on the detector window. The retrieved water vapour total vertical columns for the period 2003–2007 are compared with spatially and temporally collocated values from the European Centre for Mid-Range Weather Forecast (ECMWF) data. The observed differences for individual measurements have standard deviations not higher than 0.3 g/cm^2 and an absolute mean value smaller than 0.01 g/cm^2 with some regional excursions. The use of recently published spectroscopic data for water vapour led to a significant improvement in the agreement of the retrieved water vapour total columns and the values derived from ECMWF data. This analysis thus supports the superior quality of the new spectroscopic information using atmospheric data

Validation of six years of SCIAMACHY carbon monoxide observations using MOZAIC CO profile measurements

This paper presents a validation study of SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum Likelihood Method (IMLM) algorithm using vertically integrated profile aircraft measurements obtained within the MOZAIC project for the six year time period of 2003-2008. Overall we find a good agreement between SCIAMACHY and airborne measurements for both mean values also on a year-to-year basis as well as seasonal variations. Several locations show large biases that are attributed to local effects like orography and proximity of large emission sources. Differences were detected for individual years: 2003, 2004 and 2006 have larger biases than 2005, 2007 and 2008, which appear to be related to SCIAMACHY instrumental issues but require more research. Results from this study are consistent with, and complementary to, findings from a previous validation study using ground-based measurements (de Laat et al., 2010b). According to this study, the SCIAMACHY data, if individual measurements are of sufficient quality-good signal-to-noise, can be used to determine the spatial distribution and seasonal cycles of CO total columns over clean areas. Biases found over areas with strong emissions (Africa, China) could be explained by low sensitivity of the instrument in the boundary layer and users are recommended to avoid using the SCIAMACHY data while trying to quantify CO burden and/or retrieve CO emissions in such areas. © 2012 Author(s)

Peran Orangtua Terhadap Persepsi dan Pengetahuan Remaja Putri Tentang Menarche di Desa Kuanheun

Latar Belakang. Masa remaja merupakan masa peralihan dari masa kanak-kanak menuju dewasa. Salah satu tanda kematangan fisik dan seksual pada perempuan adalah terjadinya menarche. Peristiwa terpenting yang terjadi pada masa pubertas remaja putri adalah datangnya menstruasi pertama yang dinamakan menarche yang menjadi pertanda biologis dari kematangan seksual. Idealnya seorang remaja putri belajar atau mengetahui tentang  menstruasi dari ibunya. Tidak selamanya ibu dapat memberikan informasi tentang menstruasi karena terhalang tradisi yang menganggap tabu untuk membicarakan tentang menstruasi, sehingga mempengaruhi kualitas kesehatan selama menstruasi pada remaja. Tujuan Penelitian. Mengetahui hubungan antara peran orangtua dengan persepsi remaja putri tentang menarche di desa Kuanheun Kecamatan Kupang Barat Kabupaten Kupang. Metode Penelitian Deskriptif non-eksperimental dengan pendekatan Cross-Sectional, pada 40 remaja di desa Kuanheun, pengumpulan data menggunakan kuisioner. Analisis deskriptif dan uji Chi-Square. Hasil Penelitian: peran orang tua dengan pengetahuan remaja tentang menarche termasuk dalam kategori  baik (68,8%), uji statistik menggunakan uji Chi-Square antara peran orangtua dengan pengetahuan remaja tentang menarche tidak ada pengaruh secara signifikan dengan nilai p=0,416 (p>0,05) dan peran orang tua dengan persepsi remaja tentang menarche termasuk dalam kategori  kurang (87,5%), uji Chi-Square antara peran orangtua dengan persepsi remaja tentang menarche ada pengaruh secara signifikan dengan nilai p=0,046 (p<0,05). Kesimpulan: Peran orang tua dalam mempersiapkan menarche bagi remaja putri di desa Kuanheun termasuk dalam kategori baik, dan peran orang tua mempunyai hubungan yang bermakna dengan persepsi remaja putri tentang menarche