Beam Scanning Method Research Articles

Adhesiveness of dental resin‐based restorative materials investigated with atomic force microscopy

This study aimed to show that the polymerization contraction of dental methacrylate-based materials, when used as adhesives on hard substrate, produces voids at the material-substrate interface. This phenomenology is closely related with the nanoleakage and the sealing ability of these materials. One prime/bond system, three restorative composite resins, and one orthodontic bonding system were cured by using mirror-like glass slides as a compliance-free reference substrate. The adhesive surface was analyzed by atomic force microscopy, and the polymerization contraction of bulk material was tested by laser beam-scanning method. Nanoperiodic structure of three-dimensional (3D) images, section analysis, and roughness characteristics (R(a) and R(z)) indicated that polymerization contraction produced voids at the interface. When the adhesive surface was exposed to oral simulating fluids (water, ethanol, and lactic acid solutions), hydrolytic degradation involved some hundreds of nanometers in depth. In visible light-cured (VLC) materials, the interface porosity decreased when an irradiation pause ( approximately 2 min) was carried out during gelation.

색분산 보상을 위한 선형 첩 광섬유 격자의 Apodization

색분산 보상에 사용되는 선형 첩 광섬유 격자의 제작에 있어서 Group Delay Ripple(GDR)을 줄이기 위한 apodization 기술에 대해 이론적으로 분석하고 실험적으로 규명하고자 한다. 첩격자의 제작에는 위상 마스크를 이용한 UV 빔 스캐닝 기법을 적용하였고, PZT(Piezoelectric transducer)를 이용하여 위상 마스크를 빔 스캐닝 중에 적절하게 흔들어줌으로써 apodization이 일어나도록 하였다. 이러한 모든 과정이 컴퓨터 제어로 이루어지기 때문에 다양한 apodization 프로파일을 적용할 수 있었다. Gaussian, Raised-cosine, Blackman, 그리고 Hyperbolic tangent 등의 프로파일을 적용하여 첩격자를 제작하였으며 실험 결과 0.05 nm 구간평균 peak-to-peak GDR이 20ps 이하로 감소하였다. We theoretically and experimentally investigate the effect of apodization on the transmission characteristics of linearly chirped fiber Bragg gratings(CFBGs). Based on the UV beam scanning method along a phase mask, we fabricated several apodized CFBGs with different apodization profiles such as Gaussian, Raised-cosine, Blackman, and Hyperbolic tangent. During the UV beam scanning, the phase mask is dithered by a PZT(Piezoelectric transducer) which is precisely controlled by a computer program so that the apodization profiles can be flexibly applied to the grating. We measured the reflection spectra and group delay characteristics of CFBGs with the different apodization profiles, and compared them according to their properties such as reflectivity, sidelobes, and group delay ripple (GDR). The peak-to-peak of GDR could be suppressed to less than 20 ps.

Vibrational Probing Technique for the Nano-CMM based on Optical Radiation Pressure Control

A microprobe system with a micrometer size probe sphere is required to establish the nano-CMM that is a three dimensional coordinate measuring machine with a measuring range of mm and accuracy of nm order. In this paper, the newly developed vibrational probing technique for the microprobe sytem is presented. The principle is based on the single-beam gradient-force optical trap and the forced vibration method. An optically trapped silica particle in air is vibrated using the laser beam scanning method. Frequency response is examined to estimate the radial spring constant of the microprobe system. Fundamental measurements of a micro-step specimen fabricated using a FIB (Focused Ion Beam) process are demonstrated to investigate the position detection sensitivity.

Source of spill ripple in the RF-KO slow-extraction method with FM and AM

The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron oscillation, even when the frequency does not match with the tune in the extraction region. Thus, the spill structure during one period of the FM strongly depends on the horizontal chromaticity. They are repeated with the repetition frequency of the FM, which is the very source of the spill ripple in the RF-KO method.

Polymerization of dental composite resins using plasma light

Five visible light-cured composite resins used as restoration or adhesive materials in dentistry, were irradiated with high energy plasma light (1300 mW/cm 2), and contraction, rate of contraction, irradiation-induced temperature were analysed. A comparison was carried out with the same materials irradiated with a conventional halogen light (400 mW/cm 2). The exposure to the photoactivating lights was either continuously or sequentially in three or more intervals with 10 min between intervals. Comparing the lengths of exposure of both lights, which induced the same contraction in a given material, it was found that the exposure length to the plasma light was greatly reduced, when compared with the exposure length of the halogen light (1 : 10). Frequently, the final contraction of plasma-irradiated materials was lower, whereas the rate of contraction, as indicated by the linear dimensional variation curves obtained by laser beam scanning method, did not show significant differences between the two lights. The temperature increase induced by plasma light on the material did not exceed the temperature induced by conventional light.

Photon-induced current of polycrystalline-silicon thin-film transistors

Photon-induced current (Iph) in polycrystalline-silicon thin-film transistors (poly-Si TFTs) has been investigated using a line-shaped light beam scanning method. In the off-state region, photon-excited carriers in the channel region diffuse to the drain with the diffusion length independent of the poly-Si grain size. The diffusion length is also independent whether poly-Si is hydrogenated or not. This phenomenon is observed in both n-channel and p-channel TFTs. In the subthreshold region, Iph follows the general transport equation in poly-Si. In the inversion region, Iph is proportional only to the total amount of excited carriers in the channel.

K-1344 ビームスキャニングによる高迎角物体はく離流れのPIV計測(S15-13 翼のはく離)(S15 噴流・はく離流れの計測と制御)

Two-color dual laser beam scanning PIV is applied to the measurements of the wake vortices behind an axisymmetric paraboloid to investigate the flows with separation over the body at high angles of attack. In order to record the image with the limited scattering efficiency of small tracer particles, laser beam scanning method was employed with a 3-CCD color digital video camera. The obtained single frame/multi-exposure color PIV image was decomposed into double frame/single exposure images according to the hue component of the pixel values. The developed technique is shown to provide sufficient velocity vectors in the plane normal to the symmetric axis of the body, with the exception in vortex cores. The agreement obtained between the PIV and flow visualization results is seen to be quite reasonable.

Twinning of a Quartz Plate at Low Temperature Using a Laser Beam

We have previously reported an artificial twinning (x-axis inversion) technique that involves the thermal treatment method and the laser beam scanning method for a rotated Y-cut (RY-cut) quartz plate. The heating temperature for twinning was about 520–540°C using the thermal treatment method. Furthermore, in the laser beam scanning method, a high preheating temperature of about 480°C was necessary to obtain a well-controlled twinning pattern. We present here twinning at low temperature (350°C ∼ room temperature) using the laser beam scanning method. This method can be used the potential to form an arbitrary fine twinning pattern at room temperature. High reproducibility of a fine twinning pattern was obtained at a preheating temperature of 350°C. A relatively good twinning pattern was also obtained by the laser beam scanning method without preheating. It was estimated that the shear strain caused by laser irradiation was of the order of 10-4, for the case there the twinning occurred. The large temperature gradient produced in the plate by laser beam irradiation drastically reduced the treatment temperature.

Analysis and Modeling of Surface Waviness Inspection with Light Reflection, Part 1: Laser Beam Scanning Method

The laser beam scanning method for inspecting a reflective surface has been studied with analytical derivations and numerical modeling. Specular reflection off the surface was assumed and mathematical relations consistent with analytic geometry were used to trace the laser beam and predict its screen projection. It was found that deviation of the screen projection is proportional to the surface slope along the projection direction at the reflecting point and the distance from the point to the screen. The 3-D modeling was validated with 2-D analytical relationship as a special case and was tested with a profiled SMC (sheet molding compound) panel. The screen projections of reflected laser scans off surfaces with typical features of interest are predicted and the effects of waviness orientation are investigated.

9733323 Clarification of a three-dimensional diffusion spray mechanism using the multi-impingement-wall spray image analysis using the semiconductor laser beam scanning method Song Fei (Nippon Institute of Technology Graduate School), Kyoko Okamoto, Masaru Ogura (Nippon Institute of Technology), Noboru Tazima (Nippon Institute of Technology)

9733323 Clarification of a three-dimensional diffusion spray mechanism using the multi-impingement-wall spray image analysis using the semiconductor laser beam scanning method Song Fei (Nippon Institute of Technology Graduate School), Kyoko Okamoto, Masaru Ogura (Nippon Institute of Technology), Noboru Tazima (Nippon Institute of Technology)

Simulation of spiral beam scanning for uniform irradiation on a large target

A new circular beam scanning method for uniform irradiation over a large area has been developed. A beam follows a spiral trajectory on a target, which guarantees continuous circular irradiation. A scanning speed and a trajectory spacing in a radial direction are invariable to make a particle distribution uniform. A radial position of a beam spot and an angular frequency of the spiral scanning are expressed by an irrational function of time. Relative variation in a two-dimensional particle distribution has been investigated by using a simulation program. In case a radial pitch of the spiral trajectory is much smaller than a beam width, uniformity of the particle distribution depends completely on the ratio of the minimum radius of the trajectory to the beam width. Less than ±10% uniformity of the particle distribution can be obtained for the minimum radius to beam-width ratio of less than 0.3.

A method to correct defocused element distribution maps in electron probe microanalysis

Element distribution maps obtained on electron microprobes via the beam scan method with wavelength-dispersive spectrometers reveal a defocusing effect if they are taken at sufficiently small magnification. This effect, which occurs where the Bragg condition of the spectrometer is not adequately met, can be avoided or corrected by various methods. A method is presented here to correct defocused element distribution maps with the help of corresponding maps obtained on homogeneous standards.

Les cyclotrons pour la protonthérapie de haute énergie

An accelerator designed for radiotherapy should satisfy requirements on penetration depth in tissue, maximum dose rate in the tumour and beam scanning in the target volume. - The choice of a fixed energy cyclotron simplifies the design and the operation of the accelerator. In order to reduce the overall cost of the facility it might be worth reducing the size of the cyclotron by choosing surperconducting magnet (this technology is already used in hospital for MRI). Simple beam scanning methods, compact gantries for delivering the beam under various angles and the stability of the beam intensity are of the utmost importance. - Examples of projects for medical cyclotrons have been given : a classical cyclotron in Boston, a compact superconducting cyclotron, a superconducting cyclotron with separated sectors developed in South Africa, a post-accelerators cyclotron to boost lower-energy accelerators in view of high energy protontherapy.

Optical-disk media fabrication for high data-transfer rate

Two media fabrication methods are developed in order to improve the data-transfer rate of optical disks. One is a beam-scanning method for multispiral pregroove recording. A sixfold spiral pregroove with a 1.6-µm spacing can be recorded with this method. The other is a method for fabrication of phase-change optical-disk media that provides signal reading at 670 nm, writing at 830 nm, and high erasability at high linear velocity. The linear recording density of disks fabricated in this way is 1.2 times higher than that of optical disks read at 830 nm, and the erasability is more than 25 dB at 40 m/s. These methods offer the possibility of a data transfer rate 10 times higher than with conventional methods.

Characteristics of Excimer-Laser-Crystallized Polysilicon Films by Line Beam Scanning Method

AbstractCharacteristics of polysilicon films, crystallized by excimer laser annealing, have been investigated. The entire amorphous silicon film of 50 mm X 50 mm has been crystallized by scanning a line shape excimer laser beam, which basically reduces the nonuniformity in the beam overlap region of the 2-dimensional scanning method. The laser beam had a Gaussian profile in the scanning direction, which ensured good crystallization by the reversible transitions between the crystalline and amorphous states and was expected to give step annealing effect The laser energy density and substrate temperature were varied.

Magnetic scanning system for heavy ion therapy

Beams of heavy ions have favourable physical and biological properties for the use in radiotherapy. These advantages are most pronoucced if the beam is delivered in a tumor-conform way by active beam scanning. A magnetic scanning technique is used to spread the beam laterally. The range of the particles in tissue is controlled by the variation of the beam energy in the accelerator. Computer simulations were used to compare a discrete scan mode (pixel scan) with a continous scan mode (raster scan). It was found that both methods lead to nearly identical results. The design and technical realization of the magnetic scanning system at GSI combines features of both scan techniques. First results using the lateral beam scanning method as well as the combination of the active energy variation with the magnetic beam scanning are presented.

Feasible cone beam scanning methods for exact reconstruction in three-dimensional tomography

Feasible cone beam scanning methods that permit exact reconstruction in three-dimensional tomography are proposed, and their performances are investigated using the theory developed by Kirillov [Sov. Math. Dokl. 2, 268 (1961)], Tuy [SIAM J. Appl. Math. 43, 546 (1983)], and Smith [IEEE Trans. Med. Imaging MI-4, 14 (1985)]. The proposed methods move an apex of a cone on two circles that are perpendicular to each other (orthogonal scan) or on a few twists of a helical curve (helical scan). The obtainable information, the feasibility of reconstruction, and the redundancy of measurement by some typical cone beam scanning methods are analyzed using the relationship between the cone beam projections and the three-dimensional Radon transform. Consequently it is found that the proposed methods can obtain the complete information about the three-dimensional Fourier transform of an object with less redundant measurement. Moreover, based on the analysis, a practically implementable reconstruction algorithm suitable for the proposed methods is derived. Experiments performed with both numerical and real x-ray projections demonstrate the validity of the proposed scanning methods and the reconstruction algorithm. Especially when a large cone angle is used, the proposed methods greatly improve the spatial resolution and the quantitative accuracy of reconstruction as compared with the method of circular apex motion.

Multidirectional Holographic Scanner For Point-Of-Sale Bar-Code Symbol Reader

A multidirectional laser beam scanning method using holographic zone plates is described. To increase the number of scanning directions, not only is a hologram disk rotated at fixed speed (col ), but a laser beam incident on the disk is reversely rotated at another speed (w2). The focus of the laser beam diffracted by the hologram disk draws multidirectional scanning lines. The number of scanning directions (n) is equal to (w1 /c02) + 1. Experimentally, the effectiveness of this method is demonstrated for nineteen scanning directions. This scan method is applied to a point-of-sale (POS) scanner to read a non-moving bar-code symbol.

Optical probing of the inhomogeneous gap distribution in nonequilibrium superconductors

The laser beam scanning method has been applied to study a spatial gap distribution in nonequilibrium superconducting films. The small gap region locates around the center of the junction area and its extreme splits into two parts. The large gap lies in the circumferential region.

Measurement of Void Distribution in Transient Flows

By means of X-ray Beam Scanning Method, void distributions in horizontal pipes during blowdown were measured for various conditions. Two types of X-ray void fraction meters were used; One was scanning upward and downward across the pipes, and the other was highspeed scanning type using a rotating disc. Highspeed scanning type had a void distribution color display system that made it easy to recognize even a slug flow. The data were plotted on the flow regime map and compared with available data. For high mass flux. the flow pattern became annular and was weakly dependent on pressure. For low mass flux, the flow pattern became stratified due to gravity.