Search

Digitization offers a solution to the challenges associated with managing and retrieving paper-based documents. However, these paper-based documents must be converted into a format that digital machines can comprehend, as they primarily understand alphanumeric text. This transformation is achieved through Optical Character Recognition (OCR), a technology that converts scanned image documents into a format that machines can process. A novel top-down character segmentation approach has been proposed in this work, involving multiple stages. Our approach began by isolating lines from handwritten documents and using these lines to segment words and characters. To further enhance the character segmentation, a Raster Scanning object detection technique is employed to isolate individual characters within words. Thus, the character segmentation results are integrated from the results of the vertical projection and raster scanning. Recognizing the significance of advancing digitization of handwritten documents, we have chosen to focus on the regional languages of Assam and Andhra Pradesh due to their historical and cultural importance in India's linguistic diversity. So, we have collected datasets of handwritten texts in Assamese and Telugu languages due to their unavailability in the desired form. Our approach achieved an average segmentation accuracy of 93.61%, 85.96%, and 88.74% for lines, words, and characters for both languages. The key motivation behind opting for a top-down approach is two-fold: firstly, it enhances the accuracy of character recognition, and secondly, it holds the potential for future use in language/script identification through the utilization of segmented lines and words. [ABSTRACT FROM AUTHOR]

Background: Using the pencil beam raster scanning method employed at most carbon beam treatment facilities, spots can be moved without interrupting the beam, allowing for the delivery of a dose between spots (move dose). This technique is also known as Dose‐Driven‐Continuous‐Scanning (DDCS). To minimize its impact on HIMAK patient dosimetry, there's an upper limit to the move dose. Spots within a layer are grouped into sets, or "break points," allowing continuous irradiation. The beam is turned off when transitioning between sets or at the end of a treatment layer or spill. The control system beam‐off is accomplished by turning off the RF Knockout (RFKO) extraction and after a brief delay the High Speed Steering Magnet (HSST) redirects the beam transport away from isocenter to a beam dump. Purpose: The influence of the move dose and beam on/off control on the dose distribution and irradiation time was evaluated by measurements never before reported and modelled for Hitachi Carbon DDCS. Method: We conducted fixed‐point and scanning irradiation experiments at three different energies, both with and without breakpoints. For fixed‐point irradiation, we utilized a 2D array detector and an oscilloscope to measure beam intensity over time. The oscilloscope data enabled us to confirm beam‐off and beam‐on timing due to breakpoints, as well as the relative timing of the RFKO signal, HSST signal, and dose monitor (DM) signals. From these measurements, we analyzed and modelled the temporal characteristics of the beam intensity. We also developed a model for the spot shape and amplitude at isocenter occurring after the beam‐off signal which we called flap dose and its dependence on beam intensity. In the case of scanning irradiation, we measured move doses using the 2D array detector and compared these measurements with our model. Result: We observed that the most dominant time variation of the beam intensity was at 1 kHz and its harmonic frequencies. Our findings revealed that the derived beam intensity cannot reach the preset beam intensity when each spot belongs to different breakpoints. The beam‐off time due to breakpoints was approximately 100 ms, while the beam rise time and fall time (tdecay) were remarkably fast, about 10 ms and 0.2 ms, respectively. Moreover, we measured the time lag (tdelay) of approximately 0.2 ms between the RFKO and HSST signals. Since tdelay ≈ tdecay at HIMAK then the HSST is activated after the residual beam intensity, resulting in essentially zero flap dose at isocenter from the HSST. Our measurements of the move dose demonstrated excellent agreement with the modelled move dose. Conclusion: We conducted the first move dose measurement for a Hitachi Carbon synchrotron, and our findings, considering beam on/off control details, indicate that Hitachi's carbon synchrotron provides a stable beam at HIMAK. Our work suggests that measuring both move dose and flap dose should be part of the commissioning process and possibly using our model in the Treatment Planning System (TPS) for new facilities with treatment delivery control systems with higher beam intensities and faster beam‐off control. [ABSTRACT FROM AUTHOR]

The use of ultrafast cylindrical vector vortex beams in laser–matter interactions permits new ablation features to be harnessed from inhomogeneous distributions of polarization and beam geometry. As a consequence, the ablation process can yield higher ablation efficiency compared with conventional Gaussian beams. These beams prevent surface quality degradation during the ablative processes. When processing stainless steel and titanium, the average surface roughness obtained by deploying the cylindrical vector is up to 94% lower than the Gaussian case, and the processing efficiency is 80% higher. [ABSTRACT FROM AUTHOR]

As in various manufacturing processes, in sliding tests with scanning motions to extend the sliding distance over fresh countersurface, temperature rise during any pass is bolstered by heating during prior passes over neighboring tracks, providing a "heat accumulation effect" with persisting temperature rises contributing to an overall temperature rise of the current pass. Conduction modeling is developed for surface temperature rise as a function of numerous inputs: power and size of heat source; speed and stroke length, and track increment of scanning motion; and countersurface thermal properties. Analysis focused on mid-stroke location for passes of a square uniform heat flux sufficiently far into the rectangular patch being scanned from the first pass at its edge that steady heat accumulation effect response is adopted, focusing on maximum temperature rise experienced across the pass' track. The model is non-dimensionalized to broaden the applicability of the output of its runs. Focusing on practical "high" scanning speeds, represented non-dimensionally by Peclet number (in excess of 40), applicability is further broadened by multiplying non-dimensional maximum temperature rise by the square root of Peclet number as model output. Additionally, investigating model runs at various non-dimensional speed (Peclet number) and reciprocation period values, it appears these do not act as independent inputs, but instead with their product (non-dimensional stroke length) as a single independent input. Modified maximum temperature rise output appears to be a function of only two inputs, increasing with decreasing non-dimensional values of stroke length and scanning increment, with outputs of models runs summarized compactly in a simple chart. [ABSTRACT FROM AUTHOR]

Odd-harmonic repetitive control (ORC) has been successfully applied to improve the triangular trajectory tracking performance of nanopositioners. However, the conventional ORC tends to amplify the tracking errors at frequencies other than the odd-harmonic components, mainly the even harmonics of the fundamentals of the intended triangular trajectory to be tracked. Due to the influence from the hysteresis nonlinearity of the piezoelectric actuator, this would result in significant tracking errors. To overcome this limitation, this article proposes an enhanced odd-harmonic repetitive control (EORC) using the spectrum-selection filtering scheme to improve the loop-shaping property of the ORC. This effectively eliminates the problem of amplifying the tracking errors while preserving the advantages of the conventional ORC, such as fast convergence speed and low computation cost. The EORC is combined with a proportional–integral tracking controller to improve the tracking performance. The controller design, stability analysis, and performance evaluation are presented. The experimental results demonstrating the effectiveness of the proposed EORC-based control scheme are presented showing the excellent tracking of triangular trajectories with fundamental frequencies up to 1000 Hz. Moreover, a reduction in rms tracking errors by up to 52% is achieved. Note to Practitioners—The high-speed atomic force microscopy (AFM) plays an increasingly vital role in observing and manipulating objects at the nanoscale. In the raster scanning of AFMs, the most challenging issue is the triangular trajectory tracking of nanopositioning stages with high precision. Although the odd-harmonic repetitive control (ORC) has been successfully applied to improve the tracking performance, the conventional ORC would amplify the tracking errors distributed at the frequencies other than the odd harmonics, especially those at the even harmonics, resulting from the inherent complicated hysteresis nonlinearity. This problem of amplifying the tracking errors would lead to larger tracking errors, deteriorating the performance of AFM imaging. To address this issue, this article proposes an enhanced ORC using the spectrum-selection filtering scheme to improve the loop-shaping property of the ORC, so as to eliminate the problem of amplifying the tracking errors while preserving the advantages of the conventional ORC, such as fast convergence speed and low computation cost. The experimental results show that, with this simple modification, the positioning errors are reduced greatly, all-the-while preserving the benefits of the conventional ORC scheme– fast convergence speed and low computation cost. In terms of tracking accuracy and the simple structure, this development can be easily implemented to other systems that challenge from the tracking accuracy under ORC scheme. [ABSTRACT FROM AUTHOR]

This paper presents an efficient architecture for two-dimensional (2-D) adaptive FIR filter architecture using the distributed arithmetic (DA) algorithm. DA-based filter architectures essentially require look-up tables (LUT). In the proposed filter architecture, RAM- or ROM-based LUT is replaced by adders- and logic gates-based structure that generates the LUT value corresponding to the input. Therefore, the MAC unit requires fewer logic gates and adders in DA-based realization. In addition, the memory sharing concept in architecture reduces the delay elements. Moreover, the complexity of the LUT hardware of higher-order filters is reduced by parallelly dividing the internal MAC block for the DA decomposition which offers a higher degree of modularity and parallelism in the proposed architecture. Further, 2-D delayed LMS algorithm is used for the updation of the filter coefficient weights. Furthermore, two-stage pipelining is used to reduce the critical path of the architecture and it also makes critical path delay independent of the order of the filter. ASIC synthesis results reveal the advantages of the proposed structure by reducing the area, power, ADP and EDP by 54%, 48.19%, 55% and 49%, respectively, as compared with the existing architecture for filter size 8 × 8. [ABSTRACT FROM AUTHOR]

The scanning speed of atomic force microscopes (AFMs) is typically limited by the frequency of the triangular trajectory used in generating the raster scan. This is because the higher harmonics of the triangular trajectory have a tendency to excite the mechanical resonances of the nanopositioners incorporated in the AFM; thereby, introducing significant positioning errors. To address this issue, this article proposes a novel scanning trajectory smoothing method to enable high-speed raster scanning. The proposed method utilizes the acceleration-continuous B-spline to replace the backward path of the triangular trajectory for the fast axis. As a result, the advantage of uniform sampling along the forward path is preserved. The trajectory generation process is described in detail. A hysteresis compensation method is employed to improve the tracking performance of the scanner. Experiments conducted on a commercial piezoelectric tube scanner are presented to demonstrate the performance improvement delivered by the proposed method when compared with the traditional raster scanning method. It is shown that the proposed method enables a five-fold improvement in achievable scanning rate, from 10 to 50 Hz. [ABSTRACT FROM AUTHOR]

To develop a Monte Carlo (MC) beam model for raster scanning proton beams for dose verification purposes. MC program FLUKA was used in the model. The nominal energy, momentum spread and beam angular distribution in the model were determined by matching the simulation profiles with the measured integral depth dose (IDD) and in air spot size. Dosimetric comparison was done by comparing the measured and simulated dose distributions. The 1 D dose profile of cubic Spread Out Bragg Peak (SOBP) plans, and the 2 D dose distribution of previously treated breast cancer patients' clinical plans were measured by using Pinpoint chambers and 2 D array ionization chambers, respectively. Corresponding DICOM plan information was utilized for MC simulation. The MC results showed good agreement with measurements for the SOBP plans. The absolute comparison of the absorbed dose difference between the MC and the measurement was 0.93%±0.88%. For the patient plans, the overall passing rate of the gamma index analysis (γ-PR) between the MC simulation and measurement with the 2%-2 mm criteria was 97.78%, and only 1 case had a γ-PR less than 90%. With the 3%-3 mm criteria, γ-PR was never below 99% for all cases with and without the range shifter. This work described a method for adapting a MC simulation model for a raster scanning proton beam. The good concordance between the simulations and measurements shows that the MC model is an accurate and reliable method. It has the potential to be used for patient specific quality assurance (PSQA) to reduce the beam time for the measurements in water. [ABSTRACT FROM AUTHOR]

Featured Application: Non-destructive inspection of plastic and ceramic products. Terahertz (THz) technology offers unique see-through imaging capability for various non-destructive inspection applications. In this work, we implemented a broadband continuous-wave THz imaging system to study technical issues related to the see-through imaging, including frequency-dependent resolution, material loss, and interference-induced artifacts. The interference-induced false contrast and artifacts were observed, which were suppressed by broadband imaging techniques adopting the homodyne signal amplification by interferometric setup to overcome the material loss. [ABSTRACT FROM AUTHOR]

The special features of the implementation and the main sources of measurement uncertainty of the power of an ultrasound beam in water are examined by the method of plane scanning of the cross-section of a beam. The methods of evaluating the effect of deviations from the conditions of a plane wave and a far field were refined. Methods of decreasing the laboriousness of measuring beams with rotational symmetry are substantiated. The results are presented for the comparison of the values of the power of ultrasound emission of a round piston emitter, obtained by the plane scanning method and by the reference method of equilibration of emission force. The sufficiently good concurrence of the results provides evidence of the potential possibility of increasing the precision of hydrophone calibrations by the methods of plane (raster or diametral) scanning. [ABSTRACT FROM AUTHOR]

During the raster scanning of atomic force microscopes (AFMs), the coupling effect from the fast-axis to the slow-axis is extraordinarily pernicious, especially when the scanning rate is set high. Whilst great efforts have been made in the field of piezo-actuated stages, less attention is paid on control design to mitigate this coupling effect. In this paper, we propose a modified repetitive control based cross-coupling compensation (MRC-CCC) approach for high-speed and high-precision scanning motion control of a piezoelectric tube scanner in AFMs. Based on the experimental observations, we first describe this coupling effect as the periodic disturbance to the output of the slow-axis when the fast-axis is designed to track triangular trajectories. Then, the MRC-CCC controller is developed to remedy the periodic disturbances, which generates the compensation signals targeting the coupling effect. Therefore, the complicated modeling of the cross-coupling effect is avoided, which significantly reduces the complexity of usage. To ensure the high-precision tracking performance for the slow-axis in scanning, we further design a tracking controller that combines with the offline trained MRC-CCC controller. Finally, comparative experiments are conducted on an AFM piezoelectric tube scanner. Experimental results show that the developed MRC-CCC approach significantly compensates for the coupling effect, in which the root-mean-square tracking error is substantially reduced from 172.1 to $3.3\text{ nm}$ at the scanning rate of 40 Hz. We also perform high-speed scanning tests for AFM imaging to verify the effectiveness of the development. [ABSTRACT FROM AUTHOR]

The resolution and accuracy of terahertz (THz) imaging depend on the scanning distance between raster pixels. Recently, numerous studies have focused on increasing scanning speed and accuracy. The current study presented a high-speed scanning method without dwell time during scanning. A compensation factor for the velocity in a motorized x-y linear stage with a scanning sample was introduced to maintain the high accuracy of image scanning with the proposed method. The THz imaging system consisted of fiber-coupled pulsed photoconductive antenna and motorized x-y linear stage based on THz-time-domain spectroscopy. A validation specimen was fabricated by using copper tape and acrylic plate to compare the image scanning performance of various methods. Reflection mode scanning with 90° incident angles was conducted on the validation sample. The performance of the proposed scanning method without dwell time was evaluated and compared with that of other methods in terms of scanning speed, which is defined as the number of pixels per second; and geometric matching ratio, which uses modal assurance criterion (MAC) to quantify scanning accuracy. Results confirmed that the scanning speed of the proposed method is 328 % faster than that of conventional scanning methods and that the MAC value of the geometric matching ratio is more than 0.994 without any additional equipment installation. [ABSTRACT FROM AUTHOR]

An optimized synchrotron‐based X‐ray diffraction method is described for the direct and efficient measurement of crystallite phase and orientation at micrometre resolution across textured polycrystalline samples of millimetre size (high scale dynamics) within a reasonable time frame. The method is demonstrated by application to biomineral fish otoliths. Otoliths are calcium carbonate accretions formed in the inner ears of vertebrates. Fish otoliths are essential biological archives, providing information for individual age estimation, the study of population dynamics and fish stock management, as well as past environmental and climatic conditions from archaeological specimens. Here, X‐ray diffraction mapping is discussed as a means of describing the mineralogical structure and microtexture of otoliths. Texture maps could be generated with a few a priori hypotheses on the aragonitic system. Full‐section imaging allows quantitative intercomparison of crystal orientation coupled to microstructural description, across the zones of the otoliths that represent distinctive mineral organization. It reveals the extents of these regions and their internal textural structure. Characterization of structural and textural correlations across whole images is therefore proposed as a complementary approach to investigate and validate the local in‐depth nanometre‐scale study of biominerals. The estimation of crystallite size and orientational distribution points to diffracting domains intermediate in size between the otolith nanogranules and the crystalline units, in agreement with recently reported results. [ABSTRACT FROM AUTHOR]

This paper presents a generalized formulation of 2-D IIR filters using distributed arithmetic (DA) techniques. Based on the DA formulation, two efficient structures for 2-D IIR filters are proposed. Hardware-based look-up table (HLUT) is used in the internal blocks, so the proposed structures are reconfigurable. A novel approach of HLUT sharing, among the various internal blocks of structure, is used to reduce the requirement of adders and memory elements. For higher-order 2-D IIR filter, the complexity of HLUT is reduced by dividing the internal block of 2-D IIR filter into parallel and small block for DA decomposition. Such decomposition for higher-order 2-D IIR filters offers high degree of modularity, parallelism and regularity in building blocks, thereby achieving easier hardware and software implementation. In order to reduce combinational delay in the critical path, pipelining is used in the structures. Since proposed structures are multiplier-less and require lesser number of delays and adders, a significant improvement in chip area, power consumption and throughput can be obtained. Finally with the help of ASIC synthesis results, a comparative analysis is made and the results show that for the filter order 15, the proposed structures offer 69 and 59% reduction in ADP and 79 and 76% reduction in ADP than the earlier reported results for separable and non-separable structures, respectively. [ABSTRACT FROM AUTHOR]

We propose a differential-type complementary metal-oxide-semiconductor (CMOS) sub-terahertz (THz) detector with a subthreshold preamplifier. The proposed detector improves the voltage responsivity and effective signal-to-noise ratio (SNR) using the subthreshold preamplifier, which is located between the differential detector device and main amplifier. The overall noise of the detector for the THz imaging system is reduced by the preamplifier because it diminishes the noise contribution of the main amplifier. The subthreshold preamplifier is self-biased by the output DC voltage of the detector core and has a dummy structure that cancels the DC offsets generated by the preamplifier itself. The 200 GHz detector fabricated using 0.25 μm CMOS technology includes a low drop-out regulator, current reference blocks, and an integrated antenna. A voltage responsivity of 2020 kV/W and noise equivalent power of 76 pW/ √ Hz are achieved using the detector at a gate bias of 0.5 V, respectively. The effective SNR at a 103 Hz chopping frequency is 70.9 dB with a 0.7 W/m2 input signal power density. The dynamic range of the raster-scanned THz image is 44.59 dB. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND Local control in patients with adenoid cystic carcinoma (ACC) of the head and neck remains a challenge because of the relative radioresistance of these tumors. This prospective carbon ion pilot project was designed to evaluate the efficacy and toxicity of intensity-modulated radiotherapy (IMRT) plus carbon ion (C12) boost (C12 therapy). The authors present the first analysis of long-term outcomes of raster-scanned C12 therapy compared with modern photon techniques. METHODS Patients with inoperable or subtotally resected ACC received C12 therapy within the pilot project. Whenever C12 was not available, patients were offered IMRT or fractionated stereotactic radiotherapy (FSRT). Patients received either C12 therapy at a C12 dose of 3 Gray equivalents (GyE) per fraction up to 18 GyE followed by 54 Gray (Gy) of IMRT or IMRT up to a median total dose of 66 Gy. Toxicity was evaluated according to version 3 of the Common Toxicity Terminology for Adverse Events. Locoregional control (LC), progression-free survival (PFS), and overall survival (OS) were analyzed using the Kaplan-Meier method. RESULTS Fifty-eight patients received C12 therapy, and 37 received photons (IMRT or FSRT). The median follow-up was 74 months in the C12 group and 63 months in the photon group. Overall, 90% of patients in the C12 group and 94% of those in the photon group had T4 tumors; and the most common disease sites were paranasal sinus, parotid with skull base invasion, and nasopharynx. LC, PFS, and OS at 5 years were significantly higher in the C12 group (59.6%, 48.4%, 76.5%, respectively) compared with the photon group (39.9%, 27%, and 58.7%, respectively). There was no significant difference between patients who had subtotally resected and inoperable ACC. CONCLUSIONS C12 therapy resulted in superior LC, PFS, and OS without a significant difference between patients with inoperable and partially resected ACC. Extensive and morbid resections in patients with advanced ACC may need to be reconsidered. The most common site of locoregional recurrence remains in field, and further C12 dose escalation should be evaluated. Cancer 2015;121:3001-3009. © 2015 American Cancer Society. [ABSTRACT FROM AUTHOR]

High-resolution structural information was obtained from lysozyme microcrystals (20 µm in the largest dimension) using raster-scanning serial protein crystallography on micro- and nano-focused beamlines at the ESRF. Data were collected at room temperature (RT) from crystals sandwiched between two silicon nitride wafers, thereby preventing their drying, while limiting background scattering and sample consumption. In order to identify crystal hits, new multi-processing and GUI-driven Python-based pre-analysis software was developed, named NanoPeakCell, that was able to read data from a variety of crystallographic image formats. Further data processing was carried out using CrystFEL, and the resultant structures were refined to 1.7 Å resolution. The data demonstrate the feasibility of RT raster-scanning serial micro- and nano-protein crystallography at synchrotrons and validate it as an alternative approach for the collection of high-resolution structural data from micro-sized crystals. Advantages of the proposed approach are its thriftiness, its handling-free nature, the reduced amount of sample required, the adjustable hit rate, the high indexing rate and the minimization of background scattering. [ABSTRACT FROM AUTHOR]

We have enhanced photoacoustic microscopy with three-dimensional arbitrary trajectory (3-DAT) scanning, which can rapidly image selected vessels over a large field of view (FOV) and maintain a high signal-to-noise ratio (SNR) despite the depth variation of the vessels. We showed that hemoglobin oxygen saturation (sO2) and blood flow can be measured simultaneously in a mouse ear in vivo at a frame rate 67 times greater than that of a traditional two-dimensional raster scan. We also observed sO2 dynamics in response to switching from systemic hypoxia to hyperoxia. [ABSTRACT FROM AUTHOR]

A nonresonant, fiber-optic raster scanning endomicroscope was developed using a quarter-tubular piezoelectric (PZT) actuator. A fiber lever mechanism was utilized to enhance the small actuation range of the tubular PZT actuator and to increase its field-of-view. Finite element method simulation of the endoscopic probe was conducted for various conditions to maximize its scanning range. After fabricating the probe using a double clad fiber, we obtained two-photon fluorescence images using raster beam scanning of the fiber. The outer diameter of the probe was 3.5 mm and its rigid distal length was 30 mm including a high numerical aperture gradient index lens. These features are sufficient for input into the instrumental channel of a commercial colonoscope or gastroscope to obtain high resolution images in vivo. [ABSTRACT FROM AUTHOR]

Infrared (IR) spectromicroscopy, or chemical imaging, is an evolving technique that is poised to make significant contributions in the fields of biology and medicine. Recent developments in sources, detectors, measurement techniques and speciman holders have now made diffraction-limited Fourier transform infrared (FTIR) imaging of cellular chemistry in living cells a reality. The availability of bright, broadband IR sources and large area, pixelated detectors facilitate live cell imaging, which requires rapid measurements using non-destructive probes. In this work, we review advances in the field of FTIR spectromicroscopy that have contributed to live-cell two and three-dimensional IR imaging, and discuss several key examples that highlight the utility of this technique for studying the structure and chemistry of living cells. [ABSTRACT FROM AUTHOR]

Background: In combined proton-carbon fixed-nozzle treatment facilities with raster scanning delivery, the scattering of proton pencil beams caused by nozzle elements and the relatively large nozzle-to-isocenter distance cause a beam broadening. This may pose limitations to the achievable dose conformity. One way to counteract this effect is by delivering the treatment in a position closer to the nozzle than the room isocenter. Purpose of this study was to assess the potential dosimetric benefit of such solution, in terms of dose conformity and normal tissue sparing, in intensity-modulated proton therapy (IMPT) of intracranial tumors.Material and Methods: For 12 patients with intracranial lesions, IMPT-plans were created at two treatment positions: nozzle-to-treatment-isocenter distance: 100 cm (room isocenter) and nozzle-to-treatment-isocenter distance: 60 cm. The resulting plans were compared in terms of dose distributions, dose-volume histograms and selected dosimetric indexes.Results: With comparable target coverage, statistically significant normal tissue sparing was achieved through the reduction of the distance between nozzle and treatment isocenter. The decrease in mean dose (Dmean) was 12.5% to the whole brain, 16.2% to the brainstem, 9.7% and 15.4% to the temporal lobes, 10.0% and 12.9% to the hippocampi, 11.8% and 12.5% to the optic nerves and 0.2% to the chiasm. The volume receiving at least 10% of the prescribed dose (V10%) was reduced by more than 10% for most organs at risk (OARs). The maximum dose (Dnear-max) values to most OARs remained without significant difference.Conclusion: A reduced distance between nozzle and treatment isocenter leads to steeper lateral dose gradients and significantly reduces the volume of OARs adjacent to the target, which receives low to intermediate doses. Technical solutions shifting the treatment isocenter closer to the nozzle should be considered in clinical situations, where critical OARs are adjacent to the beam channel and where the integral dose should be minimized. [ABSTRACT FROM AUTHOR]

Possible ways of improving laser image generators based on the circular scanning principle are analyzed. The most important sources of errors induced by the system of radial displacements and by the rotation unit are studied. Principles of decreasing the main components of instability of operation of image generators with circular scanning are described. Owing to the use of some principles, the prototype of such a generator can be put onto the second place in the worldwide rating of systems used by various companies to form structures providing high-accuracy measurements of angles (scales, limbs, rasters, etc.). [ABSTRACT FROM AUTHOR]

A compliant XY nanopositioner is presented in this brief. The device is designed to have a very low cross-coupling between the X - and Y -axis. Despite this, during high-speed raster scans, the cross-coupling effect can not be ignored. In this brief, a H∞ controller is designed and implemented to minimize the X -to-Y cross-coupling of the nanoscale positioning stage, particularly at its mechanical resonance frequencies. The controller is augmented with integral action to achieve accurate tracking, as well as sufficient damping. Raster scan results over an area of 10 µm 10 µm with small positioning errors are demonstrated. High-speed accurate raster scans of up to 100 Hz, with nanoscale resolution are also illustrated. [ABSTRACT FROM AUTHOR]

We introduce a backside island isolation method for silicon-on-insulator (SOI)-based microelectromechanical systems technology and demonstrate vertical comb drive-based two-dimensional gimbaled micromirrors with large static rotation using the isolation method. The proposed isolation method provides electrical isolation and mechanical coupling of SOI structures without additional dielectric backfill and planarization by utilizing timed etched backside handle wafer structures. The backside island is a hidden layer beneath the gimbal and allows independent application of actuation potentials to the gimbal and inner mirror. We developed the fabrication process that accommodates the backside island isolation structures into an established vertical comb drive process, thereby allowing implementation of two-axis gimbaled structures. The maximum static optical deflections of the gimbal and mirror are 46° and 15°, respectively. [ABSTRACT FROM PUBLISHER]

Femtosecond laser engraving offers appealing advantages compared to regular laser engraving such as higher precision and versatility. In particular, the inscription of deep patterns exhibits an increasing interest in industry. In this work, an optimization protocol based on constraining overlap ratio and scan number is demonstrated. The proposed method allows changing overlap ratio while maintaining depth in the same range, which reduces the sampling number. This study WAS applied to stainless steel 316 L and sapphire for engravings deeper than 100 μ m. Results exhibit overall depths higher than threshold values and allowed to determine optimized engraving quality, for instance, roughness in steel can be reduced while maintaining depth and taper angle by reducing overlap ratio. The optimized laser parameters such as roughness and taper angle factors for sapphire were also found to be as follows: 200 kHz, 86% overlap and 12 J/cm 2 . As a demonstration, a logo engraving is illustrated at the end. [ABSTRACT FROM AUTHOR]

An algorithm for Cartesian trajectory generation by redundant robots in environments with obstacles is presented. The algorithm combines a raster scanning technique, genetic algorithms and functions for interpolation in the joint coordinates space in order to approximate a desired Cartesian curve by the robot's hand tip under maximum allowed position deviation. A raster scanning technique determines a minimal set of knot points on the desired curve in order to generate a Cartesian trajectory with bounded position approximation error. Genetic algorithms are used to determine an acceptable robot configuration under obstacle avoidance constraints corresponding to a knot point. Robot motion between two successive knot points is finally achieved using well known interpolation techniques in the joint coordinates space. The proposed algorithm is analyzed and its performance is demonstrated through simulated experiments carried out on planar redundant robots. [ABSTRACT FROM AUTHOR]

We describe the design, fabrication, and experimental results of a raster scanning laser display system using micromachined electrostatic scanning micromirror. The micromirror is comprised of a diaphragm mirror plate supported by an array of diamond shaped support frame, and movable comb electrodes. A prototype raster scanning laser display system using the fabricated micromirror, having optical scan angle of 16.9deg at resonance frequency of 19.55 kHz, as the horizontal scanner was developed and tested. To compensate for the nonlinear characteristics of the scanner, a simple image correction method was developed, and the projected image was analyzed and compared with the simulation results [ABSTRACT FROM PUBLISHER]

Here, we propose a technique that utilizes a Nipkow disk and an integrating sphere for the fast acquisition of millimeter-wave images. This technique has the potential for quietly achieving video frame rates. A demonstration of the principle is made in the optical region. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 32: 440–442, 2002. [ABSTRACT FROM AUTHOR]