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The extraordinary graphene material has brought about extensive attention in space engineering for outstanding characteristics. The reduced graphene oxide paper (rGOP) was irradiated by 500 keV proton in a ground-based irradiation simulator. The results show that the spacing of layer to layer was increased after irradiation, while the oxygen functional group was decreased. The result of XPS and Raman spectroscopy indicates that the sp3 carbon and defects increased, and the disorder structure in high fluence irradiated materials also increased. Furthermore, the performance degradation for thermal stability and electrical property of rGOP is contributed to the combination of defects and disordered structure.

Surface-enhanced Raman scattering (SERS) is highly promising for ultra-sensitive detection in a series of applications. Although extensive advances have been achieved in SERS technologies, the preparation of highly efficient SERS substrates still suffers from several limitations, including complex preparation procedures, high cost, and instability for long time storage. To address these problems, we report a novel, to the best of our knowledge, SERS platform that combines graphene oxide (GO) and cellulose composite paper with colloidal silver nanoparticle (Ag NP) ink. As an efficient substrate, the GO and cellulose composite paper that features hierarchical micro-nanostructures and improved interaction with target molecules can be fabricated on a large scale, and the Ag NP ink can be well stored, avoiding being oxidized in ambient conditions. In this way, our SERS platform not only reduces the cost, but also improved the stability. The sensitivity, reproducibility, and tunable SERS detection performance were evaluated using rhodamine 6G as probing molecules. To demonstrate the capability of our SERS platform in practical analysis, the SERS spectra of two monosodium salt solutions of different concentrations have been collected. The SERS platform has revealed great potential for practical application of SERS technologies.

The effect of variation of radio frequency (rf) power on the structural, optical and electronic properties of intrinsic hydrogenated amorphous silicon (a-Si:H) films deposited at very low substrate temperature (Ts) 110 °C were studied. These films were prepared varying rf power (40-70 W) on borosilicate glass, photo paper and c-Si substrates using rf-plasma enhanced chemical vapour deposition (13.56 MHz) technique. All films show amorphous structure confirmed by Raman measurement and also supported by spectroscopic ellipsometry (SE) measurements. SE results show that at higher rf power, amplitude of peak decreases and broadening increases due to increase in void density. Intrinsic layer with optimized rf power was used for fabricating n-i-p solar cell on flexible polyethylene terephthalate (PET), polyimide (PI), photo paper and rigid glass. The efficiency of solar cells fabricated on flexible PET and PI is 3.30% and 3.36%, which is close to 3.82% on rigid glass. In case of solar cells on photo paper, an efficiency of ~ 1.08% was obtained. The studies show that it is possible to fabricate a-Si:H based solar cells on photo paper and other substrates at very low Ts.

In this study, we developed a cost-effective ion-sensing field-effect transistor (FET) with an extended gate (EG) fabricated on a separative paper substrate. The pH sensing characteristics of the paper EG was compared with those of other EGs fabricated on silicon, glass, or polyimide substrates. The fabricated paper-based EGFET exhibited excellent sensitivity close to the Nernst response limit as well as to that of the other substrate-based EGFETs. In addition, we found that all EGFETs, regardless of the substrate, have similar non-ideal behavior, i.e., drift phenomenon and hysteresis width. To investigate the degradation and durability of the paper EG after prolonged use, aging-effect tests were carried out in terms of the hysteresis width and sensitivity over a course of 30 days. As a result, the paper EG maintained stable pH sensing characteristics after 30 days. Therefore, we expect that paper EGFETs can provide a cost-effective sensor platform.

The Uplink Wavefront Corrector System (UWCS) is a pathfinder instrument to demonstrate the uplink correction by Adaptive Optics techniques; this novel application can be directly usable in two fields: Free-Space Optical Communications and the generation of Laser Guide Stars. A Rayleigh LGS is propagated to the sky while the atmospheric wavefront aberrations are measured by a Shack-Hartmann WFS with 12 x 12 sub-apertures using a Natural Guide Star as a reference. The laser upwards propagation path is then pre-compensated by a 97-actuator deformable mirror. A scoring camera is attached to the finder telescope, next to the main aperture, in order to show the overall result, which is assessed in terms of beam power concentration. Present paper described the design process of the UWCS and its integration and testing in the Optical Ground Station telescope, at Teide Observatory (Spain).

In order to assess the moisture content of insulating pressboard in oil-immersed transformer, and thus providing reliable guidance for insulation condition and life estimation of oil-immersed transformer, in this paper, we made four groups of oil-paper insulation samples with different moisture content under laboratory conditions and studied the relationship between pressboard and moisture content by using polarization and depolarization current (PDC) technique. The experiment result shows that PDC curve is very sensitive to the change of moisture content, and the change of moisture content mainly affects the tail of depolarization current curve; the extended Debye model parameters can be obtained from depolarization current curve, and as the moisture content increases the number of branches in Debye model increases, the largest time constant becomes large; the peak of time domain spectroscopy turn up at 1000s., the time constant branch which is longer than 1000s presents the pressboard branches of Debye model; the feature quantity Q paper can show the internal polarization of insulating paper and has a linear fitting relationship with moisture content, so Q paper can be used to assess the moisture content of insulating pressboard.

This study investigates why a silver nanoparticle (SNP)-induced surface-enhanced Raman scattering (SERS) paper chip fabricated at low successive ionic layer absorption and reaction (SILAR) cycles leads to a high SERS enhancement factor (7 × 10 8 ) with an inferior nanostructure and without generating a hot spot effect. The multi-layered structure of SNPs on cellulose fibers, verified by magnified scanning electron microscopy (SEM) and analyzed by a computational simulation method, was hypothesized as the reason. The pattern of simulated local electric field distribution with respect to the number of SILAR cycles showed good agreement with the experimental Raman intensity, regardless of the wavelength of the excitation laser sources. The simulated enhancement factor at the 785-nm excitation laser source (2.8 × 10 9 ) was 2.5 times greater than the experimental enhancement factor (1.1 × 10 9 ). A 532-nm excitation laser source exhibited the highest maximum local electric field intensity (1.9 × 10 11 ), particularly at the interparticle gap called a hot spot. The short wavelength led to a strong electric field intensity caused by strong electromagnetic coupling arising from the SNP-induced local surface plasmon resonance (LSPR) effects through high excitation energy. These findings suggest that our paper-based SILAR-fabricated SNP-induced LSPR model is valid for understanding SNP-induced LSPR effects.

Recent advances in the production and development of two-dimensional transition metal dichalcogenides (2D TMDs) allow applications of these materials, with a structure similar to that of graphene, in a series of devices as promising technologies for optoelectronic applications. In this work, molybdenum disulfide (MoS2) nanostructures were grown directly on paper substrates through a microwave-assisted hydrothermal synthesis. The synthesized samples were subjected to morphological, structural, and optical analysis, using techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman. The variation of synthesis parameters, as temperature and synthesis time, allowed the manipulation of these nanostructures during the growth process, with alteration of the metallic (1T) and semiconductor (2H) phases. By using this synthesis method, two-dimensional MoS2 nanostructures were directly grown on paper substrates. The MoS2 nanostructures were used as the active layer, to produce low-cost near-infrared photodetectors. The set of results indicates that the interdigital MoS2 photodetector with the best characteristics (responsivity of 290 mA/W, detectivity of 1.8 &times, 109 Jones and external quantum efficiency of 37%) was obtained using photoactive MoS2 nanosheets synthesized at 200 &deg, C for 120 min.

In this Letter, a refractive index measurement of a dielectric sample using highly focused radially polarized light is reported. Through imaging analysis of the optical field at the pupil plane of a high numerical aperture (NA) objective lens reflected by the sample under study, the Brewster angle is found. Employing a high NA objective lens allows the measurement of multiple angles of incidence from 0° to 64° in a single shot. The refractive index of the sample is estimated using the measured Brewster angle. The experimental results are compared with the theoretical images computed with the Fresnel theory, and a good agreement is obtained.

Historic works on paper, illuminated (painted) or unpainted manuscripts, and textiles are fragile and nearly impossible to sample. Non-invasive techniques such as visible microscopy, X-ray fluorescence, Raman, and reflectance spectroscopy are commonly used to determine the artist material present. Recently, nonlinear optical ultrafast pump-probe microscopy was shown to provide non-invasive, high-resolution mapping of pigments in historic paintings to investigate paint stratigraphy. In this paper, we combine our pump-probe contrast with nonlinear fluorescence and second-harmonic generation contrasts exhibited by fibrous supports composed of natural bio-materials (cellulose, collagen, or lignin). Hence, our multi-modal nonlinear microscope is able to simultaneously investigate pigments in conjunction with their support in three dimensions with micrometer-scale spatial resolution. Here we examine the utility of nonlinear pump-probe microscopy by studying a series of mock-up samples, including indigo-dyed cotton cloth, ultramarine blue painted on various types of paper, and papers painted with mixtures and layers of the two pigments. In each case we find that we can combine pump-probe pigment contrast with nonlinear optical fiber contrast to obtain spatial information that is otherwise unavailable to the conservator.

The insulation diagnosis method based on frequency domain dielectric spectrum is widely used in field test because of its nondestructive testing, rich insulation information and so on. FDS measurement results are easy to be affected by many factors. However, interpretation on the dielectric properties of oil paper insulation with moisture content, impurity ion concentration influence mechanism of the current research is not very ideal, so it is necessary to determine more appropriate and effective dielectric response simulation and experimental analysis of characteristics. In addition, moisture content (m.c.) is an extremely important factor which can determine the insulation state of Oil-immersed paper. Therefore, the evaluation of moisture content of oil-immersed paper has obvious significance. In this paper, based on the experimental results, the extended Debye model parameters of the field transformer are obtained. Then, the influence of the insulation resistance value in the Debye model on the FDS curve is simulated by MATLAB modeling. The simulation and experimental verification show that the regularity of the change of the FDS conductance process is obviously different from the moisture content influenced by the impurity ions. The impurity ions mainly affect the low frequency section of the imaginary part of the complex capacitor. A non-linear phenomenon in dielectric response with different moisture contents under different is observed. We found that the non-linear phenomenon has relationship with the hindrance effect of cellulose (m.c.

The paper describes an approach to fabricate large area Graphene (Gr)/MoS 2 on paper using simple, cost effective solution processed hydrothermal method. Gr was deposited on paper using dip coating method followed by hydrothermal growth of 2D MoS 2 on Gr. Raman analysis confirmed the growth of few layer MoS2. IV characteristic of MoS 2 , MoS2/Gr revealed higher conductivity for Gr/MoS 2 . Under illumination 31.84 % and 55.33 % decrease in resistance was observed for MoS 2 and Gr/MoS2 based devices respectively indicating that Gr/MoS 2 based devices are more sensitive compared to MoS2. Successful fabrication of flexible paper based Gr/MoS 2 photodetector is a step ahead in large area, low cost electronic applications.

A simple approach to calculate the amplitude component of a wave front propagating in space from a hologram is proposed. It is able to calculate the amplitude distribution on a plane at any distance rapidly using a standard GPU. This is useful for analyzing and reconstructing the 3D image encoded on a hologram.

Wide range grade of pencils were used to draw on variety of sheet of papers. Raman spectroscopy and multimeter evaluate graphite structure and resistance of the area on the drawn paper before laser irradiation. The 10B grade of lead pencil draw on silver-halide print paper, and femtosecond laser was employed to irradiate the area of various papers drown by 10B lead pencil with varied scanning speed and laser power. At optimal conditions of laser irradiation, Raman spectroscopy verified the multi-graphene on the B10 pencil drawn silver-halide print paper irradiated by femtosecond laser.

Confocal laser scanning microscopy was applied to visualize inside fibers stained with a fluorescent dye, and the fiber orientation distribution in the thickness direction was determined by image analysis from optically sliced images. Fiber orientation angle and anisotropy were determined by the fast Fourier transform method, which holds advantages over the conventionally applied Hough transform with regard to evaluation of fiber width-weighted contribution and intrafiber segmental contribution. An orthogonally layered Japanese paper handmade by the flow-sheet forming method resulted in a clear change of fiber orientation angle from 0° to 90°. Machine-made wood-containing printing paper showed the highest anisotropy, while copier paper showed a low anisotropy. Thick papers like the wood-free paperboard and recycled packaging board showed that the maximum measured thickness was about 150 μm. The depth limit to detect fluorescence was considered to depend on the apparent density of the paper and the light absorption character of the fibers.

IR monitoring is a basic tool for quality control and predictive maintenance in the paper industry. There are also other possible interests, e.g. measurements of temperature profiles of high speed production lines. The first possibility to use IR for the above mentioned use appears to be applications of glass heat treatment in on line production. At this time there is a lot of interest to be able to measure temperature profiles from a fast moving surface (e.g. in paper machines) with velocities like 10 - 20 m/s. Normal low speed line scanners typically give scanning speed of 50 Hz which in this case means 20 m/s/50 Hz equals 40 cm resolution. The obtained resolution is not normally high enough. To have more accurate vision from the studied surface IR camera line scanning was proposed to be a solution with line scanning frequencies of 8000 Hz which would provide resolution of 20 m/s/8000 Hz equals 0.25 cm between surface points. It is a well-known fact that all undesired frequencies in paper transfer systems disturb the uniform paper drying process which in some cases is the basic reason for low quality coating or even broken paper line. The possibility to detect these drying problems with IR frequency analysis will give a new way to control the paper drying process. With IR analysis it is possible to get information about temperature distributions along the paper track. Using a well established frequency analysis as a tool, the error estimations are obtained. In most cases an open-roll image from paper track is very desirable because there are no existing wide area measurement systems for this purpose. The careful analysis of this new method is given in the manuscript.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

It is shown that the work entitled “Conversion of Laguerre-Gaussian beams into Gaussian beams of reduced focal spot by use of a circular echelon” repoted by S.Cherif et al. (Optik 127 (2016) 3134–3137), follows the same procedures as presented in the papers of the authors ([A. Hasnaoui, A.Bencheikh and K.ait ameur, Opt. Lasers Eng. 49 (2011) 248–251], [A. Hasnaoui, A. Bencheikh, M. Fromager, E. Cagniot, K. Ait-Ameur, Creation of a sharper focus by using a rectified TEMp0beam, Opt. Commun. 284 (2011) 1331–1334]), but concludes that their results are substantially different from the results of the authors. We find that there is no new result in the whole work, in addition there are big mistakes that we look to clarify and to correct.

We present preparatory measurements for an improved test of time dilation at the experimental storage ring (ESR) at GSI in Darmstadt. A unique combination of particle accelerator experiments and laser spectroscopy is used to perform this test with the highest precision. 7Li+ ions are accelerated to 34% of the speed of light at the GSI Helmholtzzentrum für Schwerionenforschung and stored in the experimental storage ring. The forward and backward Doppler shifts of an electric dipole transition of these ions are measured with laser spectroscopy techniques. From these Doppler shifts, both the ion velocity β = ν/c and the time dilation factor [Formula: see text] can be derived for testing Special Relativity. Two laser systems have been developed to drive the 3S1→3P2 transition in 7Li+. Moreover, a detector system composed of photomultipliers, both to monitor the exact laser ion beam overlap as well as to optimize fluorescence detection, has been set up and tested. We investigate optical-optical double-resonance spectroscopy on a closed Λ-type three-level system to overcome Doppler broadening. A residual, broadened fluorescence background caused by velocity-changing processes in the ion beam is identified, and a background subtraction scheme implemented. At the present stage the experimental sensitivity, although already comparable with previous measurements on slower ion beams at the TSR storage ring that led to [Formula: see text] –8, suffer from a poor signal-to-noise ratio. Modifications of the ion source as well as the detection system are discussed that promise to improve the sensitivity by one order of magnitude.

The aging of oil-paper insulation in power transformers may cause serious power failures. Thus, effective monitoring of the condition of the transformer insulation is the key to prevent major accidents. The purpose of this study was to explore the feasibility of confocal laser Raman spectroscopy (CLRS) for assessing the aging condition of oil-paper insulation. Oil-paper insulation samples were subjected to thermal accelerated ageing at 120 °C for up to 160 days according to the procedure described in the IEEE Guide. Meanwhile, the dimension of the Raman spectrum of the insulation oil was reduced by principal component analysis (PCA). The 160 oil-paper insulation samples were divided into five aging stages as training samples by clustering analysis and with the use of the degree of polymerization of the insulating papers. In addition, the features of the Raman spectrum were used as the inputs of a multi-classification support vector machine. Finally, 105 oil-paper insulation testing samples aged at a temperature of 130 °C were used to further test the diagnostic capability and universality of the established algorithm. Results demonstrated that CLRS in conjunction with the PCA-SVM technique provides a new way for aging stage assessment of oil-paper insulation equipment in the field.

Existing literature shows that lower time constant branches of insulation model represent condition of oil, whereas higher time constant branches are influenced by the condition of solid insulation. It is possible to assess the condition of oil-paper insulation by identifying the parameters of insulation model. It is understood that in addition to aging and moisture, factors like insulation geometry also affect the values of the branch parameters of insulation model. This implies parameters evaluated from one insulation model has limited potential in assessing the condition of a different transformer, even if the loading history and power rating of the two units are similar. The present paper introduces a performance parameter, which is less sensitive to insulation geometry. The parameter can be evaluated from the Transfer Function of the insulation model. It is shown that the parameter is influenced by condition of both oil and paper insulation. The performance of the proposed parameter is first tested using laboratory sample and then using data obtained from several real life power transformers.

This paper presents a novel method of identifying a paper sheet by calculating the similarity of the power spectrum of a frequency analysis. Focus has been put on the wire mark in paper as a periodicityin this work.Hand sheets prepared with 5 different commercial wires provided both of ‘samples’ and ‘references’.The two-dimensional fast Fourier transform (FFT) was applied to the light-transmitted imagesof the sheets to obtain power spectra (PS). Each ‘reference’ PS file was prepared by averaging 12 PSout of 3 hand sheets per wire. This procedure is to reduce a local variation of paper. The group of thereference PS files can be considered as a database. Another sheet of the same papers was creased intentionallyto make a ‘sample’. Only a part of the sheet offered a PS for the data.Cross-correlation calculation has been adopted for the quantitative similarity calculation between PS of the samples and of the references. Wavelengths longer than approximately 1. 6 mm, herein, havebeen eliminated for the correlation calculations. Since the periodicity of a wire should be around 0.5mm and the powers of relatively longer wavelengths are remarkably large comparing to that of theshorter wavelengths, the powers of the wavelengths longer than 1.6mm lower the correlation precision.Every sample showed the highest similarity when it was coupled with the reference out of thesame wire. This implies the possible usefulness of the cross-correlation matching method applied to thepower spectrum of FFT analysis of the light-transmitted images in order to distinguish paper.

A frequency analysis has shown that the formation for wood free paper by visual ranking is determined by the power ratio of wavelength of 6.2 mm to the sum of the powers. That wavelength might be derived from the flocs in the specimens. While that for the wood contained paper is determined by the distribution of light transmission, not by any particular wavelength or waveband.A group of 183 panelists who had been familiar to paper products compared specimens of wood free-and wood contained-papers along Scheffe's method (modified by Nakaya) in a previous work. The results of this visual qualification of the formation for the specimens by this method have been named observed M-values.While an image scanner coupled with an IBM-PC/AT compatible computer captured the light transmission images of the specimens. Where the resolution of the images is 50 dpi and the depth of 256 gray levels with the dimension of A 4 area (i.e. 210 mm horizontally and 297 mm vertically).A frequency analysis of 2-dimensional fast Fourier transform has been applied onto the specimens of 256×256 pixels of area (130 mm each). The transformation produces a 2-dimensional power spectrum. Where each of the peaks shows the direction of repetition of the wave and its wavelength or its frequency. The powers of the peaks on concentric circles in the spectrum (i.e. the peaks have the identical pixel distances from the center of the spectrum) were integrated, subsequently. That makes 1-dimensional spectrum of 127 elements proportional to the inverse of the wavelength.The linear regressions for all the combinations of the wavelengths (wavebands) of 127×126/ 2 patterns have been conducted with the visual qualifications by the panelists for the wood free paper specimens. The existence ratio of the power of 6.2 mm wavelength only has shown a fair agreement. On the other hand, the case for the wood contained paper found nearly every waveband except for the longer waves approximately than 7 mm wavelength to explain the M-value. That means the distribution of gray levels of transmitted light except the longer waves determines the visual qualification.

The explosion of big data applications imposes severe challenges of data processing speed and scalability on traditional computer systems. However, the performance of the von Neumann machine is greatly hindered by the increasing performance gap between CPU and memory, motivating the active research on new or alternative computing architectures. As one important instance, neuromorphic computing systems inspired by the working mechanism of human brains have gained considerable attention. In this work, we propose a heterogeneous computing system with neuromorphic computing accelerators (NCAs) that are built with emerging memristor technology. In the proposed system, NCA is designed to speed up the artificial neural network (ANN) executions in many high-performance applications by leveraging the extremely efficient mixed-signal computation capability of nanoscale memristor-based crossbar (MBC) arrays. The hierarchical MBC arrays of the NCA can be flexibly configured to different ANN topologies through the help of an analog Network-on-Chip (A-NoC). A general approach which translates the target codes within a program to the corresponding NCA instructions is also developed to facilitate the utilization of the NCA. Our simulation results show that compared to the baseline general purpose processor, the proposed heterogeneous system can achieve on average 18.2x performance speedup and 20.1x energy reduction over nine representative applications while constraining the computation accuracy degradation within an acceptable range.

Experiments with laser generation and detection of ultrasound in copy paper indicate that earliest arrivals of ultrasound are antisymmetric. A likely explanation is that the out-of-plane interferometer is relatively insensitive to the symmetric compressional pulse because of the low Poisson ratio of copy paper, but rather sensitive to its antisymmetric flexural wake associated with the random heterogeneities and gradients present in copy paper.

Drawings were made on various types of paper using lead pencils of grades from 4H through 10B. Raman spectroscopy verified both G and D peaks on all the drawings on PC print paper, PC photopaper, kent paper, and paper for silver halide print. After irradiation with a scanning femtosecond laser, silver halide paper drawn on with a 10B lead pencil maintained its surface flatness compared with the other types of paper. Raman spectroscopy on silver print paper showed a high-intensity G peak and a low-intensity D peak. After irradiating the scanning femtosecond laser on silver halide paper drawn on with a 10B lead pencil, Raman spectroscopy showed a high-intensity G peak and less intense of D peak together with a 2D peak around 2,700 cm−1 corresponding to the existence of multigraphene.

The main physical principles of the operation of ring gas lasers in the laser-gyroscope regime are examined. The influence of nonreciprocal effects on the operational parameters of ring gas lasers and the methods of controlling, with the aid of the nonreciprocal magneto-optical Zeeman effect, the parameters of these lasers used in gyroscopes are discussed.

Strong demand exists for a non-contacting paper caliper measurement which can be used as an input to a paper thickness control system. Caliper sensors requiring sheet contact suffer from errors related to dirt or coating build up and from high maintenance costs related to wear. These sensors can also damage the product by picking holes and marking sheets. Details of an on-line measurement device which employs two opposed laser displacement sensors and an inductive displacement sensor are presented. The sheet is held perpendicularly to the sensors with a Coanda air clamp. Dust and temperature control features which enable the sensor to operate reliably in an industrial environment are discussed. Results of production trials of this sensor are presented. Sub-micron profile agreement to lab and contacting caliper measurements has been demonstrated on light sheets. Results are presented of measurements on a wide range of paper grades from coated and uncoated light sheets to coated board.

We demonstrate a time-domain terahertz technique for measuring thickness, moisture and basis weight of paper. We validate our technique for a sample compressed to different thicknesses and establish uncertainty limits using Monte Carlo simulations.

Publisher Summary In his book titled Electrical Papers , Heaviside brought together his main writings on circuit theory and the inductive properties of wires, and his thoughts on electromagnetism. The Electrical Papers offers an advanced exposition, as well as many novel contributions to two basic themes: the theory of electromagnetic field dynamics because of Maxwell and an extension of linear circuit theory to the case of continuous transmission lines. Motivation for the expansion theorem appears to reside in the generalized Ohm's law that operational impedances associate with electrical circuits. In a circuit containing standard resistance only, if the impressed voltage is given, then the current at any time may be calculated by simple division. The main product of this endeavor was a series of three long papers “On operators in physical mathematics” that were intended for publication by the Royal Society. Only the first two were published: the third was turned down in the face of stern objections raised by mathematicians to his unconventional and potentially problematic use of divergent series.

Doppler Global Velocimeters (DGV) requires a narrow bandwidth laser beam which can be accurately tuned to a desired frequency. One laser used for this application is an ND-YAG which is seeded using a laser diode. By adjusting the laser diode output, the frequency of the ND-YAG laser beam can be modified. This technique also narrows the bandwidth of the laser frequency to below 100 MHz. Monitoring this output is difficult due to the 9 ns pulse duration which makes normal interferometry techniques ineffective for the 10 to 20 MHz frequency resolution required. This paper will describe a system constructed to monitor the frequency in real time which can be used in conjunction with a DGV system to correct for laser frequency drift. The particular ND-YAG system response and stability will be presented and discussed in relationship to DGV system accuracy.Copyright © 2008 by ASME

紙のX-Y平面内の繊維配向分布のZ方向プロファイル測定法について検討した。これはフラウンホーファー回折とテープ剥離による紙層分割法を組み合わせたものである。回折像の評価に関して, シミュレートした繊維配向分布の数値計算と実験により調査した。なお, ここでは0次回折像が対象となった。これらの分析による結果は与えられた繊維配向分布と良く一致することが分った。さらに, 実機製品であるシェイキングマシン抄き紙及び高速マシン抄き紙に関して, 繊維配向のZ方向プロファイルの測定を行った。

A procedure of inspection of femtosecond laser induced mass transfer processes has been suggested that is based on pump-probe Doppler tomography. In the experiments we used mode-locked Ti:sapphire laser with output power up to 150 mW.. In our experiments focused laser radiation induced on the surface of the target mass transfer processes (melting and convection). The Doppler shifted backscattered radiation was registered by heterodyne scheme based on Michelson interferometer. We have obtained information about depth and distribution of convection flows within melted paraffin bath with high spatial resolution (Dz~15mm). We propose optical heterodyning technique based on OCT for obtaining temporal distribution of backscattered photons from media irradiated by Cr:forsterite femtosecond laser. The temporal resolution is about 60 fs. The technique was used for sheet paper porosity diagnostics.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Numerous equally-spaced emission lines can be generated by stimulated Raman scattering and subsequent four-wave Raman mixing. The spectral domain extends from the near-infrared to the deep-ultraviolet, and then an ultimately-short optical pulse can be generated by phase locking in the process of four-wave Raman mixing. In fact, an intense 17-fs optical pulse has been generated using this technique. A comb of 1.6-fs optical pulses, i.e., the shortest optical pulses, has also been generated by other researchers. On the other hand, it is possible to generate highly-repetitive pulses using a continuous wave (CW) laser as a pump source and molecular hydrogen as a Raman medium in a high-finesse cavity. Coherent superposition of the two-color beam comprising of the fundamental beam and the Stokes beam provides a sinusoidal wave modulated at 17 THz. It is also possible to generate more than three emission lines simultaneously, which should generate an impulsive wave. It is noted that such Raman emission can be generated in a hollow-core fiber, making the device extremely simple. Such a device may have a potential for use in basic science and technology, e.g., the generation of a three-primary-color laser for display.

We report our direct observation of the Barkhausen avalanche in ferromagnetic thin film systems, where a collective spin behavior produces nontrivial fluctuations in magnetization change under an external magnetic field. For this study, we develop and use two direct full-field magnetic imaging techniques: magneto-optical microscope magnetometer (MOMM) and magnetic transmission X-ray microscopy (MTXM). From a direct visualization and a statistical analysis of the fluctuating domain images for Co thin films, we investigate the scaling behavior of the Barkhausen avalanche both on spatial and temporal scales using MOMM. We also investigate the reproducibility of the Barkhausen avalanche process. Interestingly, the partially stochastic nucleation behavior is observed for CoCrPt alloy films by means of MTXM on a nanometer scale comparable to the fundamental length scales such as the Barkhausen volume and the grain size of the polycrystalline films. Via these direct full-field observation techniques, dynamic details of Barkhausen avalanche are revealed.

We discuss the basic physical principles of laser optical pumping double-resonance spectroscopy, which form the basis of state-of-the-art vapour-cell atomic frequency standards using laser optical pumping of Rb atoms. The main effects limiting the frequency stability of Rb vapour-cell atomic clocks are identified, and their impact on the development of high-performance frequency standars and their transfer from research laboratories to industry and space is discussed. As examples, the impact of the AC stark effect and the realated issue of laser frequency stabilisation are dealt with in more detail. The main features of the present state-of-the-art Rb atomic frequency standards will be illustrated using the example of the development of atomic clocks for satellite navigation and positioning systems (GPS, GLONAS, GALILEO, etc.) as well as some directions for further improvements that could overcome present day limitations. Such compact Rb clocks find their applications in, for example, telecommunications, local timekeeping and synchronisation, and space applications like satellite navigation and science missions. An overview of other, alternative clock schemes is given and critical issues for future developments towards further performance improvement or device miniaturisation in the field of vapour-cell atomic clocks are discussed.

Chalcogenide glass fibers have been developed at NRL. Rare earth doped chalcogenide glass fibers emit strong IR emission and show potential for mid-IR and long-wave IR rare earth doped fiber lasers. In addition, undoped highly nonlinear chalcogenide glass fiber compositions have been developed with high Raman cross-sections and show potential for mid-IR and long-wave IR Raman fiber lasers.

Ultrafast lasers promise to become attractive and reliable tools for material processing on micro- and nanoscale. The additional possibility to temporally tailor ultrashort laser pulses by Fourier synthesis of spectral components enables extended opportunities for optimal processing of materials. An experimental demonstration of the technique showing the possibility to design particular excitation sequences tailored with respect to the individual material response will be described, laying the groundwork for adaptive optimization in materials structuring. We report recent results related to the implementation of self-learning, adaptive loops based on temporal shaping of the ultrafast laser pulses to control laser-induced phenomena for practical applications. Besides the fundamental interest, it is shown that under particular excitation conditions involving modulated excitation, the energy flow can be controlled and the material response can be guided to improve processing results. Examples are given illuminating the possibility to control and manipulate the kinetic properties of ions emitted from laser irradiated semiconductor samples using excitation sequences synchronized with the phase transformation characteristic times.

We propose applying carbon-nanotube-composite Japanese washi paper (CNT-washi) to a secure authentication system. CNT-washi is easily made by a simple fabrication method. We used three-dimensional Raman spectrum mapping patterns from CNT-washi as a special "key" for a secure authentication system. CNTs automatically form complex patterns in the paper, and it is very difficult to copy these patterns owing to their nanometer size. We observed Raman spectra at divided areas of each CNT-washi sample and prepared mapping patterns. The observed pattern of a sample was different from those of the other samples because the variety or concentration of the CNTs differs between samples. We calculated correlation coefficients between the mapping data of the prepared samples. Experimental results indicate that the patterns of our CNT-washi can be used as a "key" for authentication systems.

The quantitative analysis of human corneal endothelial cell patterns is analyzed with Fourier transform methods. The optical or digital Fourier transform of the pattern of endothelial cell borders is analyzed to yield the average cell area and the coefficient of variation of the average cell area. The more difficult problem of cell shape characterization is still under investigation. The advantage of the Fourier transform analysis is the parallel processing of the optical Fourier transform and the potential development of a hybrid digital-optical device for the rapid analysis of large numbers of endothelial specular photomicrographs

Laser ultrasonics has great potential for monitoring the bending stiffness of paper during on‐line operations. The temperature and humidity conditions at the paper have a significant effect on the bending stiffness, and there is a need to quantify this dependence before an on‐line system can be deployed. A laser pulsed source illuminates a point on a paper sample placed inside a controlled environmental chamber and generates ultrasound that is detected by a fiberoptic interferometer. The waveform is analyzed to extract the frequency dependence of the group velocity of the A0 lamb mode, and the corresponding bending stiffness. Three different methods of signal analysis are compared: the complex wavelet transform, the short‐time Fourier transform, and the phase‐unwrapping method, which requires measurements at two locations. The error bars associated with the bending stiffness are estimated both for the intrinsic experimental errors and for the point to point variablity in the paper itself. Results are presented for temperature ranging from 25 °C to 93 °C, and for relative humidity ranging from 2% to 75%. [Work supported by the Department of Energy and the Institute of Paper Science and Technology.]

This paper describes a fast photometric stereo method, use- ful for the determination of surface-topography and reflectance. First we show how the irradiance in two images of a surface, illuminated from the left and right, respectively, can be used to determine the inclination of the surface elements. This requires a model for the light scattering proper- ties of the surface. The model used divides the scattered light into a bulk-scattered, Lambertian part and a surface-scattered, specular part. The specular part is eliminated with the help of crossed polarizers. The inclinations are integrated to give a surface height function with the help of a Wiener filter, which suppresses frequencies with an expected poor signal-to-noise ratio. Profiles measured with this method show good agreement with profiles obtained both with optical and mechanical scan- ning methods. The standard deviation between surface height measured with the different methods was about 1 mm. The ability of this method to study reflectance and topography at the same time makes it suitable for studies of the coupling between print result and surface topography. As an example, a gravure-printed paper surface with missing dots has been studied. It was found that missing dots occur at depressions, or pores, in the surface. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00109-4)

The health status monitoring of special transformers is of great significance to ensure the secure operation of the distribution network and the power quality of special transformer users. Given this background, an operation health status monitoring algorithm of special transformers is proposed in this paper based on balanced iterative reducing and clustering using hierarchies (BIRCH) and Gaussian Cloud methods (GCM). The algorithm is composed of two parts, i.e., the offline and online parts. For the offline part, the operating indexes of special transformers are extracted based on historical operating data, and Gaussian clouds of normal operating conditions of the special transformers are determined by BIRCH clustering and Gaussian cloud methods. For the online part, Gaussian clouds of real-time operating conditions of special transformers are determined by BIRCH clustering and Gaussian cloud methods based on real-time operation data. Then, the monitoring results of operating health status are determined by the distance between the standard Gaussian clouds and the real-time Gaussian clouds of special transformers. Finally, case studies for actual special transformers are performed to verify the proposed method, and the results show that the proposed model can effectively identify the abnormal operation of the special transformer.

Pattern recognition is an example of data processing for which analog processors are well suited. We can optically classify various and complicated patterns in one operation instantaneously. Unfortunately, most information is written or printed on paper. From this reason they are not suited to conventional coherent processing. In this paper a coherent optical processor which is capable of recognizing characters printed on paper is presented. It is based on quasi Fourier holography adapted to diffuse illumination of optical signals. In this case the recognition correctness is diminished a little. The experiments are carried out with conventional print letters.

Graphical abstract The article analyzes experimentally and theoretically the influence of microscope parameters on the pinhole-assisted Raman depth profiles in uniform and composite refractive media. The main objective is the reliable mapping of deep sample regions. The easiest to interpret results are found with low magnification, low aperture, and small pinholes. Here, the intensities and shapes of the Raman signals are independent of the location of the emitter relative to the sample surface. Theoretically, the results can be well described with a simple analytical equation containing the axial depth resolution of the microscope and the position of the emitter. The lower determinable object size is limited to 2–4 μm. If sub-micrometer resolution is desired, high magnification, mostly combined with high aperture, becomes necessary. The signal intensities and shapes depend now in refractive media on the position relative to the sample surface. This aspect is investigated on a number of uniform and stacked polymer layers, 2–160 μm thick, with the best available transparency. The experimental depth profiles are numerically fitted with excellent accuracy by inserting a Gaussian excitation beam of variable waist and fill fraction through the focusing lens area, and by treating the Raman emission with geometric optics as spontaneous isotropic process through the lens and the variable pinhole, respectively. The intersectional area of these two solid angles yields the leading factor in understanding confocal (pinhole-assisted) Raman depth profiles. Spearfishing is a well-known example of the effects of refraction at the boundary between two index-mismatched media. The object Greal is seen, due to refraction, as Gvir from the angle β (without knowing the depth position). The real position is obtained under the angle α. In a microscope (see inset), index mismatch deforms the image point of Greal into an image line. The pinhole substantially reduces deformations and allows the determination of the position of the point emitter G. (Cartoon designed by Sofia Anker)

We present in this paper, the electromagnetic parameters of free and shielded dielectric spherical resonators for their utilization in the millimeter-wave frequency band.