Showing papers on "Tilt (optics) published in 2014"
TL;DR: In this paper, the authors presented a theoretical study on the optimum tilt angle for flat plate collectors at different geographical locations and different time moments over a year, where the solar radiation density was estimated based on three analysis models, namely Hottel and Woertz model (the simplest), Isotropic diffuse model (Liu & Jordan model) and HDKR model (Hay-Davis-Klucker-Reindl), passing from the simplest to the most complex one.
160 citations
TL;DR: In this paper, the effect of the tilt angle scatter on the global magnetic field, especially on the evolution of the axial dipole moment, has been studied in the context of surface flux transport (SFT) simulations.
Abstract: The tilt angles of sunspot groups represent the poloidal field source in Babcock-Leighton-type models of the solar dynamo and are crucial for the build-up and reversals of the polar fields in surface flux transport (SFT) simulations. The evolution of the polar field is a consequence of Hale's polarity rules, together with the tilt angle distribution which has a systematic component (Joy's law) and a random component (tilt-angle scatter). We determine the scatter using the observed tilt angle data and study the effects of this scatter on the evolution of the solar surface field using SFT simulations with flux input based upon the recorded sunspot groups. The tilt angle scatter is described in our simulations by a random component according to the observed distributions for different ranges of sunspot group size (total umbral area). By performing simulations with a number of different realizations of the scatter we study the effect of the tilt angle scatter on the global magnetic field, especially on the evolution of the axial dipole moment. The average axial dipole moment at the end of cycle 17 (a medium-amplitude cycle) from our simulations was 2.73 G. The tilt angle scatter leads to an uncertainty of 0.78 G (standard deviation). We also considered cycle 14 (a weak cycle) and cycle 19 (a strong cycle) and show that the standard deviation of the axial dipole moment is similar for all three cycles. The uncertainty mainly results from the big sunspot groups which emerge near the equator. In the framework of Babcock-Leighton dynamo models, the tilt angle scatter therefore constitutes a significant random factor in the cycle-to-cycle amplitude variability, which strongly limits the predictability of solar activity.
132 citations
TL;DR: It is demonstrated that the flexible uniform responsive microstructures (μFUR) can dynamically manipulate liquid spreading directionality, control fluid drag, and tune optical transmittance over a large range.
Abstract: Magnetically tunable micropillar arrays with uniform, continuous and extreme tilt angles for real-time manipulation are reported. We experimentally show uniform tilt angles ranging from 0° to 57°, and develop a model to accurately capture the behavior. Furthermore, we demonstrate that the flexible uniform responsive microstructures (μFUR) can dynamically manipulate liquid spreading directionality, control fluid drag, and tune optical transmittance over a large range.
119 citations
TL;DR: In this article, the effect of the tilt angle scatter on the global magnetic field, especially on the evolution of the axial dipole moment, was studied using SFT simulations with flux input based upon the recorded sunspot groups.
Abstract: The tilt angles of sunspot groups represent the poloidal field source in Babcock-Leighton-type models of the solar dynamo and are crucial for the build-up and reversals of the polar fields in Surface Flux Transport (SFT) simulations. The evolution of the polar field is a consequence of Hale's polarity rules, together with the tilt angle distribution which has a systematic component (Joy's law) and a random component (tilt-angle scatter). We determine the scatter using the observed tilt angle data and study the effects of this scatter on the evolution of the solar surface field using SFT simulations with flux input based upon the recorded sunspot groups. The tilt angle scatter is described in our simulations by a random component according to the observed distributions for different ranges of sunspot group size (total umbral area). By performing simulations with a number of different realizations of the scatter we study the effect of the tilt angle scatter on the global magnetic field, especially on the evolution of the axial dipole moment. The average axial dipole moment at the end of cycle 17 (a medium-amplitude cycle) from our simulations was 2.73G. The tilt angle scatter leads to an uncertainty of 0.78 G (standard deviation). We also considered cycle 14 (a weak cycle) and cycle 19 (a strong cycle) and show that the standard deviation of the axial dipole moment is similar for all three cycles. The uncertainty mainly results from the big sunspot groups which emerge near the equator. In the framework of Babcock-Leighton dynamo models, the tilt angle scatter therefore constitutes a significant random factor in the cycle-to-cycle amplitude variability, which strongly limits the predictability of solar activity.
98 citations
TL;DR: The full implementation, with real-time digital image registration, corrected the residual eye motion after optical stabilization with an accuracy of ~0.05 arcmin RMS, which to the knowledge is more accurate than any method previously reported.
Abstract: Eye motion is a major impediment to the efficient acquisition of high resolution retinal images with the adaptive optics (AO) scanning light ophthalmoscope (AOSLO). Here we demonstrate a solution to this problem by implementing both optical stabilization and digital image registration in an AOSLO. We replaced the slow scanning mirror with a two-axis tip/tilt mirror for the dual functions of slow scanning and optical stabilization. Closed-loop optical stabilization reduced the amplitude of eye-movement related-image motion by a factor of 10–15. The residual RMS error after optical stabilization alone was on the order of the size of foveal cones: ~1.66–2.56 μm or ~0.34–0.53 arcmin with typical fixational eye motion for normal observers. The full implementation, with real-time digital image registration, corrected the residual eye motion after optical stabilization with an accuracy of ~0.20–0.25 μm or ~0.04–0.05 arcmin RMS, which to our knowledge is more accurate than any method previously reported.
58 citations
TL;DR: In this article, two models that can predict the voltage-dependent scattering from liquid crystal (LC)-based reflectarray cells are presented, and the validity of both numerical techniques is demonstrated using measured results in the frequency range 94-110 GHz.
Abstract: Two models that can predict the voltage-dependent scattering from liquid crystal (LC)-based reflectarray cells are presented. The validity of both numerical techniques is demonstrated using measured results in the frequency range 94–110 GHz. The most rigorous approach models, for each voltage, the inhomogeneous and anisotropic permittivity of the LC as a stratified media in the direction of the biasing field. This accounts for the different tilt angles of the LC molecules inside the cell calculated from the solution of the elastic problem. The other model is based on an effective homogeneous permittivity tensor that corresponds to the average tilt angle along the longitudinal direction for each biasing voltage. In this model, convergence problems associated with the longitudinal inhomogeneity are avoided, and the computation efficiency is improved. Both models provide a correspondence between the reflection coefficient (losses and phase-shift) of the LC-based reflectarray cell and the value of biasing voltage, which can be used to design beam scanning reflectarrays. The accuracy and the efficiency of both models are also analyzed and discussed.
54 citations
TL;DR: In this article, an extended car-following model and an electricity consumption model were proposed to study the effects of the road's slope on the electric vehicle's electricity consumption, and the numerical results showed that each electric vehicle’s electricity consumption increases with the uphill's tilt angle and decreases with the downhill's tilt angles.
Abstract: In this paper, we propose an extended car-following model and an electricity consumption model to study the effects of the road’s slope on the electric vehicle’s electricity consumption. The numerical results show that each electric vehicle’s electricity consumption increases with the uphill’s tilt angle and decreases with the downhill’s tilt angle. In addition, each electric vehicle’s electricity consumption increases with the uphill’s (downhill’s) length under a certain tilt angle.
52 citations
TL;DR: Multislice simulations were used to analyze the reliability of ADF-STEM imaging and selected-area electron diffraction for determining the thicknesses of MoS2 and WS2 specimens in the aberration-corrected TEM and both techniques proved to be applicable to distinguish monolayers from multilayers using tilt.
51 citations
TL;DR: This article explored the visual representation of magnetic tilt angles on a traditional butterfly diagram by plotting the mean area-weighted latitude of umbral activity in each bipolar sunspot group, including tilt information.
Abstract: Sunspot groups and bipolar magnetic regions (BMRs) serve as an observational diagnostic of the solar cycle. We use Debrecen Photohelographic Data (DPD) from 1974-2014 that determined sunspot tilt angles from daily white light observations, and data provided by Li & Ulrich that determined sunspot magnetic tilt angle using Mount Wilson magnetograms from 1974-2012. The magnetograms allowed for BMR tilt angles that were anti-Hale in configuration, so tilt values ranged from 0 to 360° rather than the more common ±90°. We explore the visual representation of magnetic tilt angles on a traditional butterfly diagram by plotting the mean area-weighted latitude of umbral activity in each bipolar sunspot group, including tilt information. The large scatter of tilt angles over the course of a single cycle and hemisphere prevents Joy's law from being visually identified in the tilt-butterfly diagram without further binning. The average latitude of anti-Hale regions does not differ from the average latitude of all regions in both hemispheres. The distribution of anti-Hale sunspot tilt angles are broadly distributed between 0 and 360° with a weak preference for east-west alignment 180° from their expected Joy's law angle. The anti-Hale sunspots display a log-normal size distribution similar to that of all sunspots, indicating no preferred size for anti-Hale sunspots. We report that 8.4% ± 0.8% of all bipolar sunspot regions are misclassified as Hale in traditional catalogs. This percentage is slightly higher for groups within 5° of the equator due to the misalignment of the magnetic and heliographic equators.
50 citations
TL;DR: In this paper, the authors examined wind loads on low profile, roof-mounted solar arrays, placed on large, low-rise buildings with nearly flat roofs by using scale models in a boundary layer wind tunnel.
Abstract: The author examined wind loads on low-profile, roof-mounted solar arrays, placed on large, low-rise buildings with nearly flat roofs by using scale models in a boundary layer wind tunnel. The author also examined the effects of building size and array geometry on enveloping curves of area-averaged pressure coefficients, typical of use for design. It was found that wind loads on the array increase with building size; normalizing the effective wind area by the building wall size leads to enveloping curves that collapse onto a single curve for each array geometry. For tilt angles less than 10°, there is an approximate linear increase in the pressure coefficients as the tilt angle increases. For arrays with tilt angles of 10° or more, the wind loads do not depend significantly on the tilt angle and are relatively constant. Roof zones for wind loads on solar arrays are larger than roof zones for bare roofs and depend on the array tilt angle.
49 citations
TL;DR: In this article, the effect of Earth's dipole tilt angle and interplanetary magnetic field (IMF) Bx and By components on the location of reconnection and the energy conversion at the magnetopause was studied.
Abstract: We study the effect of Earth's dipole tilt angle and interplanetary magnetic field (IMF) Bx and By components on the location of reconnection and the energy conversion at the magnetopause. We simulate southward IMF satisfying both inward- and outward-type Parker spiral conditions during three different dipole tilt angles using a global magnetohydrodynamic model GUMICS-4. We find that positive (negative) Bx contributes to the magnetopause reconnection line location by moving northward (southward) and positive (negative) dipole tilt angle by moving it southward (northward). The tilt shifts the dayside load region toward the winter hemisphere and the summer cusp toward the equatorial plane. Magnetic flux hence piles effectively in the summer hemisphere leading to increased magnetopause currents that enhance the Poynting flux through the magnetopause. We find that the intensity of the energy conversion in the generators is strongly affected by the dipole tilt angle, whereas intensity in the load region is mainly affected by IMF Bx.
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TL;DR: In this paper, a scrolling presentation of an image is smoothed by applying an RK4 solver to the tilt measurements to eliminate jitter due to hand tremors, and a virtual spring effect is applied to give the scrolling presentation a bouncy effect as the edge of the image is reached.
Abstract: In one embodiment, a method includes sending information to display an image on a screen. A scroll range for the image may be determined based on dimensions of the image. An origin position and an initial tilt of a gyroscope may also be determined for the image. Tilt measurements associated with the presentation of the image may be received as the gyroscope detects changes in tilt. A progress parameter may be determined based on at least the scroll range, the origin position, and the initial tilt. A scrolling presentation of the image may then be rendered based on the progress parameter. The scrolling presentation of the image may be smoothed by applying an RK4 solver to the tilt measurements to eliminate jitter due to hand tremors. A virtual spring effect may also be applied to give the scrolling presentation a bouncy effect as the edge of the image is reached.
TL;DR: In this paper, the design and experimental evaluation of a high-resolution micro-electro-mechanical (MEM) tilt sensor based on resonant sensing principles is presented.
Abstract: This paper reports on the design and experimental evaluation of a high-resolution micro-electro-mechanical (MEM) tilt sensor based on resonant sensing principles. The sensors incorporate a pair of double-ended tuning fork (DETF) resonant strain gauges, the mechanical resonant frequencies of which shift in proportion to an axial force induced by variations in the component of gravitational acceleration along a specified input axis. An analysis of the structural design of such sensors (using analytical and finite element modelling) is presented, followed by experimental test results from device prototypes fabricated using a silicon-on-insulator (SOI) MEMS technology. This paper reports measurement conducted to quantify sensor scale factor, temperature sensitivity, scale factor linearity and resolution. It is demonstrated that such sensors provide a ±90° dynamic range for tilt measurements with a temperature sensitivity of nearly 500 ppb/K (equating to systematic sensitivity error of approximately 0.007°/K). When configured as a tilt sensor, it is also shown that the scale factor linearity is better than 1.4% for a ±20° tilt angle range. The bias stability of a micro-fabricated prototype is below 500 ng for an averaging time of 0.8 s making these devices a potentially attractive option for numerous precision tilt sensing applications.
TL;DR: In this paper, the discrepancy between the white-light and magnetic results is found to have two main sources: a substantial fraction of the whitelight tilt angles refer to sunspots of the same polarity.
Abstract: The axes of solar active regions are inclined relative to the east-west direction, with the tilt angle tending to increase with latitude (Joy's law). Observational determinations of Joy's law have been based either on white-light images of sunspot groups or on magnetograms, where the latter have the advantage of measuring directly the physically relevant quantity (the photospheric field), but the disadvantage of having been recorded routinely only since the mid-1960s. White-light studies employing the historical Mount Wilson (MW) database have yielded tilt angles that are smaller and that increase less steeply with latitude than those obtained from magnetic data. We confirm this effect by comparing sunspot-group tilt angles from the Debrecen Photoheliographic Database with measurements made by Li and Ulrich using MW magnetograms taken during cycles 21-23. Whether white-light or magnetic data are employed, the median tilt angles significantly exceed the mean values, and provide a better characterization of the observed distributions. The discrepancy between the white-light and magnetic results is found to have two main sources. First, a substantial fraction of the white-light tilt angles refer to sunspots of the same polarity. Of greater physical significance is that the magnetograph measurements include the contribution of plage areas, which are invisible in white-light images but tend to have greater axial inclinations than the adjacent sunspots. Given the large uncertainties inherent in both the white-light and the magnetic measurements, it remains unclear whether any systematic relationship exists between tilt angle and cycle amplitude during cycles 16-23.
TL;DR: In this article, a large displacement piston motion micromirror is designed, fabricated, and tested with device features tuned to applications requiring ultralow tilt, achieving a strongly linear motion of 90 μm achievable at only 1.2 V.
Abstract: A large displacement piston motion micromirror is designed, fabricated, and tested with device features tuned to applications requiring ultralow tilt. The fabricated MEMS mirror is based on electrothermal actuation and has a footprint of 1.9 mm × 1.9 mm with a mirror aperture of 1 mm. The application optimized device holds key features of ultralow maximum tilt of 0.25 ° and a strongly linear motion of 90 μm achievable at only 1.2 V. This device is further characterized in an interferometric system to determine the piston mode and the accurate piston displacement as a function of voltage, power, and frequency.
08 Jun 2014
TL;DR: In this article, an inexpensive soiling station was developed to evaluate soiling loss at different tilt angles (0°, 5°, 10°, 15°, 20°, 23°, 30°, 33°, 40°).
Abstract: Soiling on PV modules is known to reduce PV system performance, mainly in dry arid climatic conditions. Cleaning with water or other means may become an expensive solution to the problem. For the highest annual energy production from a fixed tilt PV system, the modules are typically installed at tilt angle close to latitude angle of the system's location. Soiling loss is an interplay between terrain of the installation, tilt angle, rain frequency and rain intensity. For un-cleaned arrays in certain dusty locations, it would be better to optimize the tilt angle for maximizing transmitted radiation to the cells by adjusting the tilt angle slightly higher which would in turn minimize the soiling loss. In this work, we have developed an inexpensive soiling station which evaluates soiling loss at different tilt angles (0°, 5°, 10°, 15°, 20°, 23°, 30°, 33°, 40°). For Mesa, Arizona (a hot-dry climate), the 0° tilt angle showed a 2.02% loss whereas 23° and 33° showed soiling loss close to 1% during the first three months of 2011.
TL;DR: A pulsed-laser range finding based on differential optical-path based on signal-to-noise ratio (SNR) is proposed, and the mathematical models are developed and verified and important conclusions are deduced.
Abstract: A pulsed-laser range finding based on differential optical-path is proposed, and the mathematical models are developed and verified. Based on the method, some simulations are carried out and important conclusions are deduced. (1) Background power is suppressed effectively. (2) Compared with signal-to-noise ratio (SNR) of traditional method, SNR of the proposed method is more suitable than traditional method in long-range finding and large tilt angle of target. (3) No matter what the tilt angle of target is, it always has optimal sensitivity of zero cross as long as the differential distance is equal to the light speed multiplied by the received pulse length and there is an overlap between two echoes.
TL;DR: In this article, the effects of electromagnetic (EM) radiation mobile phone on human head with different holding positions were analyzed through simulations by applying finite-difference time domain (FDTD) method using computer simulation technology (CST)microwave studio.
TL;DR: In this paper, the shape evolution and shrinkage kinetics of cylindrical bicrystals with different tilt and mixed boundaries were studied by molecular dynamics simulations, and it was found that the shrinkage of grains with pure tilt boundaries is accompanied by grain rotation, while grains with the tilt-twist boundaries composed of dislocations with the mixed edge screw character do not rotate as they shrink.
TL;DR: In this article, the influence of the tilt and recess shape on the static and dynamic performance characteristics of the hydrostatic thrust pad bearing system having Rabinowitsch fluid model lubricant was numerically analyzed.
TL;DR: In this paper, the authors discuss the problem of determining tilt over various measurement ranges by measuring Cartesian components of the gravity acceleration with application of accelerometers that are Microelectromechanical Systems (MEMS).
Abstract: The paper discusses thoroughly a problem of determining tilt over various measurement ranges by measuring Cartesian components of the gravity acceleration with application of accelerometers that are Microelectromechanical Systems (MEMS). The presented standard and original methods are based on various mathematical relationships between the components and the pitch and the roll. Their application results in the fact that the realized measurements are characterized by different sensitivity and accuracy (experimentally evaluated to be of 0.18°–2° for a tilt sensor built of standard MEMS accelerometers). Each method is discussed in detail with regard to the respective sensitivity and accuracy of the measurement, and its application scope is determined. Essential part of the paper are guidelines for an optimal selection of the number and type of MEMS accelerometers, as well as appropriate mathematical formula, to be used in a specific case of tilt measurement.
TL;DR: This is the first hardware demonstration of coarse and fine phasing an 18-segment pupil with the James Webb Space Telescope (JWST) geometry using a single algorithm.
Abstract: We present an optical testbed demonstration of the Fizeau Interferometric Cophasing of Segmented Mirrors (FICSM) algorithm FICSM allows a segmented mirror to be phased with a science imaging detector and three filters (selected among the normal science complement) It requires no specialised, dedicated wavefront sensing hardware Applying random piston and tip/tilt aberrations of more than 5 wavelengths to a small segmented mirror array produced an initial unphased point spread function with an estimated Strehl ratio of 9% that served as the starting point for our phasing algorithm After using the FICSM algorithm to cophase the pupil, we estimated a Strehl ratio of 94% based on a comparison between our data and simulated encircled energy metrics Our final image quality is limited by the accuracy of our segment actuation, which yields a root mean square (RMS) wavefront error of 25 nm This is the first hardware demonstration of coarse and fine phasing an 18-segment pupil with the James Webb Space Telescope (JWST) geometry using a single algorithm FICSM can be implemented on JWST using any of its scientic imaging cameras making it useful as a fall-back in the event that accepted phasing strategies encounter problems We present an operational sequence that would co-phase such an 18-segment primary in 3 sequential iterations of the FICSM algorithm Similar sequences can be readily devised for any segmented mirror
Patent•
29 Jul 2014
TL;DR: In this article, a system for controlling lateral tilt of a header (24) of an agricultural machine, using gauge wheels (50) or skids (52) on lateral ends (54, 56) of the header, was presented.
Abstract: A system (34) for controlling lateral tilt of a header (24) of an agricultural machine, uses gauge wheels (50) or skids (52) on lateral ends (54, 56) of the header (24) in combination with operation in a free float mode for maintaining uniform cut height across the header (24), and automatically changes to a controlled tilt mode when one or more conditions for that mode is present. During operation in the controlled tilt mode, if a condition or conditions for free float is present, the system (34) will operate in that mode. The system (34) can also optionally damp relative up and down movements of the gauge wheels (50) or skids (52) and the header (24) on each end, and can limit the tilt in the free float mode.
TL;DR: Borbely et al. as mentioned in this paper proposed a method for determining continuously varying spatial distortions and tilt of the area detector based on the reference diffraction rings of a certified powder, which is applied to data sets measured at the Advanced Photon Source and at the European Synchrotron Radiation Facility using detectors with different physical characteristics.
Abstract: The geometry of high-energy X-ray diffraction setups using an area detector and a rotation axis is analysed. The present paper (part 1) describes the methodology for determining continuously varying spatial distortions and tilt of the area detector based on the reference diffraction rings of a certified powder. Analytical expressions describing the degeneration of Debye rings into ellipses are presented and a robust calibration procedure is introduced. It is emphasized that accurate detector calibration requires the introduction of spatial distortion into the equation describing the tilt. The method is applied to data sets measured at the Advanced Photon Source and at the European Synchrotron Radiation Facility using detectors with different physical characteristics, the GE 41RT flat-panel and the FReLoN4M detector, respectively. The spatial distortion of the detectors is compared with regard to their use in structural and strain tensor analysis, a subject treated in part 2 of the calibration work [Borbely, Renversade & Kenesei (2014). J. Appl. Cryst. Submitted].
TL;DR: A novel, highly sensitive and directional fiber tilt sensor that is based on an asymmetrical dual tapered fiber Mach-Zehnder interferometer (ADTFMZI) that can detect the non-horizontal/horizontal state of a structure and whether the test structure is tilted to clockwise or counterclockwise by measuring the spectral responses.
Abstract: This work proposes a novel, highly sensitive and directional fiber tilt sensor that is based on an asymmetrical dual tapered fiber Mach-Zehnder interferometer (ADTFMZI). The fiber-optic tilt sensor consists of two abrupt tapers with different tapered waists into which are incorporated a set of iron spheres to generate an asymmetrical strain in the ADTFMZI that is correlated with the tilt angle and the direction of inclination. Owing to the asymmetrical structure of the dual tapers, the proposed sensor can detect the non-horizontal/horizontal state of a structure and whether the test structure is tilted to clockwise or counterclockwise by measuring the spectral responses. Experimental results show that the spectral wavelengths are blue-shifted and red-shifted when the sensor tilts to clockwise (−θ) and counterclockwise ( + θ), respectively. Tilt angle sensitivities of about 335pm/deg. and 125pm/deg. are achieved in the −θ and + θ directions, respectively, when the proposed sensing scheme is utilized.
TL;DR: A model-based aberration correction algorithm is implemented in a second-harmonic microscope and the parameters of a quadratic polynomial are computed that is used to model the image quality metric directly from experimental input-output measurements.
Abstract: Optical aberrations have detrimental effects in multiphoton microscopy. These effects can be curtailed by implementing model-based wavefront sensorless adaptive optics, which only requires the addition of a wavefront shaping device, such as a deformable mirror (DM) to an existing microscope. The aberration correction is achieved by maximizing a suitable image quality metric. We implement a model-based aberration correction algorithm in a second-harmonic microscope. The tip, tilt, and defocus aberrations are removed from the basis functions used for the control of the DM, as these aberrations induce distortions in the acquired images. We compute the parameters of a quadratic polynomial that is used to model the image quality metric directly from experimental input–output measurements. Finally, we apply the aberration correction by maximizing the image quality metric using the least-squares estimate of the unknown aberration.
TL;DR: The tilt–focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series, improving on one of the main issues of tilt series-based electron tomography.
Abstract: In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt-focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller "missing wedge" artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography.
TL;DR: A tractor stability simulator has been developed to help study tractor operators’ perceptions of angles when the simulator is tilted to the side, and results showed that about 50% of the participants reported estimations of side tilt angles within ±5 degrees of the actual angles, and nearly the same percentage overestimated the actual side tilt angle.
Abstract: A tractor stability simulator has been developed to help study tractor operators’ perceptions of angles when the simulator is tilted to the side. The simulator is a trailer-mounted tractor cab equipped with hydraulic lift that can tilt the tractor cabin up to 30 degrees. This paper summarizes data from 82 participants who sat in the simulator while it was tilted. Demographic variables, estimates of tilt angles, and measured tilt angles were collected. The effects of age, gender, tractor driving experience, and frequency of operation on the estimated and measured tilt angles were analyzed. The results showed that about 50% of the participants reported estimations of side tilt angles within ±5 degrees of the actual angles, and nearly the same percentage overestimated the actual side tilt angles. Only a small percentage underestimated the angles. Older, more experienced, and male participants set higher limits on the actual angle at which they felt uncomfortable and would not drive.
TL;DR: Tablet tilt angles should include a range of 20° to 50° at minimum at minimum, and users' tilt angle preferences should include the least preferred while the self-chosen tilt angle was most preferred.
Abstract: OBJECTIVE Tablets and other mobile devices can be tilted during use. This study examined the effect of tablet tilt angles on reading performance, target-tapping performance, wrist and forearm posture, user comfort and users' tilt angle preferences. METHOD Ten participants used tablets alternating among four different tilt angles: 0°, 30°, 45°, 60° and a user selected angle. Head, neck, wrist and forearm postural data were collected, along with reading and target-tapping performance. Subjective, perceived impressions were gathered via Likert scale questions. RESULTS Neck flexion decreased significantly as tilt angle increased. The extreme tilt angles, 0° and 60°, were least preferred while the self-chosen tilt angle, averaging about 34°, was most preferred. Tapping performance was significantly better for the self-chosen tilt angle; however, this may be a practice effect. No effect of tilt was observed on reading performance or for forearm and wrist posture. CONCLUSIONS Tablet tilt angles should include a range of 20° to 50° at minimum.
TL;DR: In this paper, the authors present an experimental procedure with periodic reversal of the magnetic field for aligning position and tilt with sufficient precision for reducing the aberrations to less than one femtosecond.
Abstract: An ubiquitous focusing element for charged particles is the magnetic solenoid lens. For the case of ultrashort electron pulses, we show here that misalignment of the lens, i.e. displacement or tilt, causes significant temporal aberrations on a femtosecond time scale. Pulse-lengthening is only minimized if the beam travels on the symmetry axis. We present an experimental procedure with periodic reversal of the magnetic field for aligning position and tilt with sufficient precision for reducing the aberrations to less than one femtosecond. This method will be instrumental for advancing ultrafast electron microscopy and diffraction to ultimate temporal resolutions.