Showing papers on "Tilt (optics) published in 2015"

Fast electron diffraction tomography

Abstract: A fast and fully automatic procedure for collecting electron diffraction tomography data is presented. In the case of a very stable goniometer it is demonstrated how, by variation of the tilting speed and the CCD detector parameters, it is possible to obtain fully automatic precession-assisted electron diffraction tomography data collections, rotation electron diffraction tomography data collections or new integrated electron diffraction tomography data collections, in which the missing wedge of the reciprocal space between the patterns is recorded by longer exposures during the crystal tilt. It is shown how automatic data collection of limited tilt range can be used to determine the unit-cell parameters, while data of larger tilt range are suitable to solve the crystal structure ab initio with direct methods. The crystal structure of monoclinic MgMoO4 has been solved in this way as a test structure. In the case where the goniometer is not stable enough to guarantee a steady position of the crystal over large tilt ranges, an automatic method for tracking the crystal during continuous rotation of the sample is proposed.

Magnetic-assisted triboelectric nanogenerators as self-powered visualized omnidirectional tilt sensing system

Abstract: Magnetic-assisted triboelectric nanogenerators as self-powered visualized omnidirectional tilt sensing system

Complete Characterizations of Tilt Stability in Nonlinear Programming under Weakest Qualification Conditions

Abstract: This paper is devoted to the study of tilt stability of local minimizers for classical nonlinear programs with equality and inequality constraints in finite dimensions described by twice continuous...

Optimization of the tilt angle of solar panels for Malaysia

Abstract: This article presents a method for optimizing the tilt angle of photovoltaic module/array installed in the five sites in Malaysia. The optimization method is based on the Liu and Jordan model for solar energy incident on a tilt surface considering monthly and seasonal tilt angles. The optimization results showed that a seasonal optimum tilt angle change is recommended for the peninsular Malaysia, while a monthly optimum tilt angle change is recommended for east Malaysia comprising the states of Sabah and Sarawak. By applying the monthly optimum tilt angle, the collected yields by the PV module/array in Kuala Lumpur, Johor Bharu, Ipoh, Kuching, and Alor Setar increased by 5.03, 5.02, 5.65, 7.96, and 6.13%, respectively. On the other hand, applying the seasonal optimum tilt angle for the same regions increased the collected yields by 4.54, 4.58, 5.70, 4.11, and 5.85%, respectively.

Electrothermally actuated tip-tilt-piston micromirror with integrated varifocal capability.

Abstract: MEMS micromirrors have proven to be very important optical devices with applications ranging from steerable mirrors for switches and cross-connects to spatial light modulators for correcting optical distortions. Usually beam steering and focusing are done with different MEMS devices and tilt angles in excess of 10 degrees are seldom obtained. Here we describe a single MEMS device that combines tip/tilt, piston mode and varifocal capability into a single, low cost device with very large tilt angles. Our device consists of a 400 micron diameter mirror driven with thermal bimorphs. We have demonstrated deflection angles of ± 40 degrees along both axes, a tunable focal length which varies between −0.48 mm to + 20.5 mm and a piston mode range of 300 microns - four separately controllable degrees of freedom in a single device. Potential applications range from smart lighting to optical switches and devices for telecom systems.

Image processing method and device

Abstract: The invention discloses an image processing method and device. The method comprises the following steps: detecting the tilt angle of a terminal screen, wherein the tilt angle of the terminal screen is an acute angle between the terminal screen and the horizontal plane; when the tilt angle is smaller than a preset angle, adjusting the display angle of an image in the terminal screen, and enabling a terminal user to increase the tilt angle of the terminal screen according to the display angle of the image in the terminal screen, wherein the display angle of the image in the terminal screen is an acute angle between the image in the terminal screen and the horizontal plane. The method is used for enabling the user to change the tilt angle of a terminal through image processing on the terminal.

Calculation of optimum fixed tilt angle of PV panels depending on solar angles and comparison of the results with experimental study conducted in summer in Bilecik, Turkey

Abstract: Sunlight incidence angle varies throughout the year due to the rotation of the earth around its own axis and its elliptical orbit. While sunlight falls to the earth with steep angle in summer in the Northern Hemisphere, it falls with shallow angle in winter. Sunlight should fall with steep angle to extract maximum power from PV panels. Therefore optimum fixed tilt angles of PV panels should be changed monthly and seasonally. In the mathematical analysis of the study, the monthly, seasonal and the annual optimum fixed tilt angles of PV panels depending on solar angles are calculated for Bilecik city. In the experimental study, optimum fixed tilt angles for May, June, July and August are determined by PV panels placed at 10°, 20°, 30°, 40°, 50° and 60° tilt angles. The mathematical analysis results are compared with the experimental results.

Domain Wall Motion Across Various Grain Boundaries in Ferroelectric Thin Films

Abstract: Domain wall movement at and near engineered 10°, 15°, and 24° tilt and 10° and 30° twist grain boundaries was measured by band excitation piezoresponse force microscopy for Pb(Zr,Ti)O3 films with Zr/Ti ratio of 45/55 and 52/48. A minimum in nonlinear response was observed at the grain boundary for the highest angle twist and tilt grain boundaries, while a maximum in nonlinear response was observed at the 10° tilt grain boundaries. The observed nonlinear response was correlated with the domain configurations imaged in cross section by transmission electron microscopy.

Subaperture stitching for measurement of freeform wavefront.

Abstract: A method based on subaperture stitching for measurement of a freeform wavefront is proposed and applied to wavefronts calculated from the slope data acquired using a scanning Shack Hartmann sensor (SHS). The entire wavefront is divided into a number of subapertures with overlapping zones. Each subaperture is measured using the SHS, which is scanned over the entire wavefront. The slope values and thus the phase values of separately measured subapertures cannot be connected directly due to various misalignment errors during the scanning process. The errors lying in the vertical plane, i.e., piston, tilt, and power, are minimized by fitting them in the overlapping zone. The radial and rotational misalignment errors are minimized during registration in the global frame by using active numerical alignment before the stitching process. A mathematical model for a stitching algorithm is developed. Simulation studies are presented based on the mathematical model. The proposed mathematical model is experimentally verified on freeform surfaces of a cubic phase profile.

Dual connected Bi-Copter with new wall trace locomotion feasibility that can fly at arbitrary tilt angle

Abstract: We have developed a robot with a new control mechanism in order to collect information on flying robots in multiple fields. We aimed for a function that could rotate the tilt angle continuously and without limit and a function for flying maintaining any desired tilt angle with a structure that could efficiently use the thrust generated by the propellers. We devised a mechanism that connected two bicopter modules, each of which combines two of the four propellers into one set and named this mechanism the “Bi2 Copter”. This mechanism provided movements including landing, take-off, and flying with any desired tilt angle. This ability of this mechanism to fly walls with continuously changing surface angles and full 360° spherical coverage makes possible applications in investigation, measurement, etc. This report covers the design concepts of this flying robot, the structure design, basic control and operations verification.

Single Channel Self-Mixing Interferometer Measures Simultaneously Displacement and Tilt and Yaw Angles of a Reflective Target

Abstract: We show that a self-mixing interferometer can supply not only to the usual optical-phase signal cos 2ks( $t$ ) of the external reflector displacement $s(t)$ , but also the attitude signal $P(a$ ) because of the dependence of power from the angle a between wavevector k and normal n to the target reflective surface. By proper interrogation of $P(a$ ) along two orthogonal components of tilt and yaw, the two angles can be measured simultaneously, together with the displacement, in a single self-mixing interferometer channel implemented by a single-laser diode and monitor photodiode combination.

Sunspot areas and tilt angles for solar cycles 7-10

Abstract: Aims. Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims to estimate areas of sunspots observed by Schwabe in 1825−1867 and to calculate the tilt angles of sunspot groups. Methods. The sunspot sizes in Schwabe’s drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Results. Umbral areas for about 130 000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier rejection method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, average to 5. ◦ 85 ± 0. 25, with the leading polarity located closer to the equator, in good agreement with tilt angles obtained from 20th century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided at the CDS.

Review: Tilt-Free Low-Noise Seismometry

Abstract: Inertial instruments used to measure horizontal motion are sensitive to tilt. Tilt coupling induced by gravity exerting a force along the sensing axis of the instrument as a function of its inclination must be accounted for in numerous seismological studies and seismic isolation applications. There are, in theory, many ways to separate tilt and horizontal motion components by combining the measurements of several sensors, and produce tilt‐free estimations of the horizontal motion. This article reviews these configurations and analyses limitations related to sensor noise and geometrical couplings. It concludes with a discussion on the use of suspension mechanisms as an alternative to signal subtraction methods.

Comparison of Debrecen and Mount Wilson/Kodaikanal sunspot group tilt angles and the Joy's law

Abstract: The study of active region tilt angles and their variations in different time scales plays an important role in revealing the subsurface dynamics of magnetic flux ropes and in understanding the dynamo mechanism. In order to reveal the exact characteristics of tilt angles, precise long-term tilt angle data bases are needed. However, there are only a few different data sets at present, which are difficult tobe compared and crosscalibrate because of their substantial deviations. In this paper, we describe new tilt angle data bases derived from the Debrecen Photoheliographic Data (DP D) (1974–) and from the SOHO/MDI-Debrecen Data (SDD) (1996-2010) sunspot catalogues. We compare them with the traditional sunspot group tilt angle data bases of Mount Wilson Observatory (1917-85) and Kodaikanal Solar Observatory (1906-87) and we analyse the deviations. Various methods and filters are investigated which may improve the sample of data and may help deriving better results based on combined data. As a demonstration of the enhanced quality of the improved data set a refined diagram of the Joy’s law is presented.

Simultaneous Measurement of Tilt Angle and Temperature With Pendulum-Based Fiber Bragg Grating Sensor

Abstract: A fiber optic tilt senor for simultaneous measurement of 2-D tilt angle and temperature is proposed and demonstrated experimentally. The sensing head consists of two fiber Bragg gratings (FBGs) attached on a specially designed columnar pendulum. Reflection peaks of the FBGs split and resonant wavelengths shift with tilt and temperature variations. A maximum tilt angle sensitivity of 0.074 nm/°, accuracy of 0.18°, and temperature sensitivity of 0.021 nm/°C have been achieved within the tilt angle range of 0°–40°.

All-on-4 concept: a 3-dimensional finite element analysis.

Abstract: The aim of this work was to study the biomechanical behavior of an All-on-4 implant-supported prosthesis through a finite element analysis comparing 3 different tilt degrees of the distal implants....

Direct Flux Measurements from Mobile Platforms at Sea: Motion and Airflow Distortion Corrections Revisited

Abstract: Ship-based measurements of wind speed and direct fluxes are affected by airflow distortion that can lead to a tilt of the wind vector as well as acceleration or deceleration of the wind speed. Direct flux measurements are additionally affected by the fluctuating velocity of the platform. The classic approach is to first correct the wind speed for angular and translational platform velocities and thereafter rotate the wind vector into the mean flow. This study finds that for ships under way, this leads to an overestimation of the vector tilt and biased flux estimates. This may explain the common observation that flux estimates from ships in transit have lower quality than measurements taken on station. Here an alternative approach is presented, where the flow-distortion-induced tilt of the wind vector is estimated from the 3D wind speed measurements and applied to the apparent wind vector. The tilt correction is carried out after correction for the fluctuating part of the platform velocity but befo...

Reconciliation of local and long-range tilt correlations in underdoped La2-xBaxCuO4(0 ≤ x ≤ 0.155)

Abstract: A long standing puzzle regarding the disparity of local and long range CuO₆ octahedral tilt correlations in the underdoped regime of La₂₋xBaxCuO₄ is addressed by utilizing complementary neutron powder diffraction and inelastic neutron scattering (INS) approaches. Long-range and static CuO₆ tilt order with orthogonally inequivalent Cu-O bonds in the CuO₂ planes in the low temperature tetragonal (LTT) phase is succeeded on warming through the low-temperature transition by one with orthogonally equivalent bonds in the low temperature orthorhombic (LTO) phase. In contrast, the signatures of LTT-type tilts in the instantaneous local atomic structure persist on heating throughout the LTO crystallographic phase on the nanoscale, although becoming weaker as temperature increases. Analysis of the INS spectra for the x = 1/8 composition reveals the dynamic nature of the LTT-like tilt fluctuations within the LTO phase and their 3D character. The doping dependence of relevant structural parameters indicates that the magnitude of the Cu-O bond anisotropy has a maximum at x = 1/8 doping where bulk superconductivity is most strongly suppressed, suggesting that the structural anisotropy might be influenced by electron-phonon coupling and the particular stability of the stripe-ordered phase at this composition. The bond-length modulation that pins stripe order is found to more » be remarkably subtle, with no anomalous bond length disorder at low temperature, placing an upper limit on any in-plane Cu-O bondlength anisotropy. The results further reveal that although appreciable octahedral tilts persist through the high-temperature transition and into the high temperature tetragonal (HTT) phase, there is no significant preference between different tilt directions in the HTT regime. As a result, this study also exemplifies the importance of a systematic approach using complementary techniques when investigating systems exhibiting a large degree of complexity and subtle structural responses. « less

Verification of computational optimum tilt angles of a photovoltaic module using an experimental photovoltaic system

Abstract: Determination of the optimum tilt angles of a photovoltaic module is of great importance because the power of photovoltaic module is highly dependent on the incident solar radiation. The purpose of this research was to verify the computational optimum tilt angles of a PV module by conducting an experimental research in Kerman-Iran. For achieving this, first, the optimum tilt angles were found using a computational model which predicts the module output energy at different tilt angles. Second, monthly, seasonal, biannual, and annual optimum tilt angles of a photovoltaic module were measured. The experimental optimum tilt angles were obtained based on 1 year measured data of the output energies of photovoltaic modules. The experiments were carried out by measuring the output electrical power of six photovoltaic modules which were inclined toward the south at different tilt angles throughout the year. The experimental optimum tilt angles were then determined based on the maximum output energy of the PV modules. Finally, the computational optimum tilt angle and the experimental optimum tilt angle were compared with each other. The results showed differences between the calculated and the measured optimum tilt angles of a PV module in the region under investigation. It was revealed that the measured annual optimum tilt angle is higher than the calculated annual optimum tilt angle. This difference was due to lack of the environmental parameter influences such as dust deposition on the PV front surface in the computational model. This study clearly showed that fixing the photovoltaic module based on the calculated annual optimum tilt angles decreases 3% the electrical output energy of photovoltaic module throughout the year compared with that fixed at the experimental optimum tilt angle. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 1156–1165, 2015

Edge enhancement of potential field data using an enhanced tilt angle

Abstract: We present an edge-detection technique for the enhancement of potential field data, which is based on the tilt angle of the first order vertical derivative of the total horizontal gradient. The tec...

Molecular Simulation of the DPPE Lipid Bilayer Gel Phase: Coupling between Molecular Packing Order and Tail Tilt Angle.

Abstract: The structural properties and thermal stability of dipalmitoylphosphatidylethanolamine (DPPE) in the ordered gel phase have been studied by molecular dynamics simulation using two force fields: the Berger united-atom model and the CHARMM C36 atomistic model. As is widely known, structural features are sensitive to the initial preparation of the gel phase structure, as some degrees of freedom are slow to equilibrate on the simulation time scale of hundreds of nanoseconds. In particular, we find that the degree of alignment of the lipids’ glycerol backbones, which join the two hydrocarbon tails of each molecule, strongly affects the tilt angle of the tails in the resulting structures. Disorder in the backbone correlates with lower tilt angles: bilayer configurations initiated with aligned backbones produced tilt angles near 21° and 29° for the Berger and C36 force fields, respectively, while structures initiated with randomized backbone orientations showed average tilt angles of 7° and 18°, in closer agreem...

Laterally Tilting Treadmill Deck

Abstract: A treadmill includes a running deck. The running deck includes a front portion, a rear portion connected to the front portion by a first side and a second side, a tread belt surrounding the front portion and the rear portion, a motor to drive movement of the tread belt, and an actuator that cause the running deck to tilt laterally towards either the first side or the second side to form a lateral tilt angle in response to a tilt command.

Sunspot areas and tilt angles for solar cycles 7-10

Abstract: Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims at estimating areas of sunspots observed by Schwabe in 1825-1867 and at calculating the tilt angles of sunspot groups. The sunspot sizes in Schwabe's drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Umbral areas for about 130,000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier rejection method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, place the leading polarity on average 5.85+-0.25 closer to the equator, in good agreement with tilt angles obtained from 20th-century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided online.

Vanishing tilt-to-length coupling for a singular case in two-beam laser interferometers with Gaussian beams

Abstract: The omnipresent tilt-to-length coupling in two-beam laser interferometers, frequently a nuisance in precision measurements, vanishes for the singular case of two beams with identical parameters and complete detection of both beams without clipping. This effect has been observed numerically and is explained in this manuscript by the cancellation of two very different effects of equal magnitude and opposite sign.