Tilted Plane Research Articles

Influence of time discrimination methods on ranging distribution of pulsed laser detecting tilted plane

Based on the traditional laser radar equation, the incoherent pulsed laser echo equation of tilted plane is derived. Combined with the working principles of leading edge discriminator (LED) and constant fraction discriminator (CFD) methods, the analytical expressions of probability density function (PDF) of two methods are derived respectively. According to these formulas, the influences of different plane inclination angle, transmitting power, pulse width and noise on the ranging distribution are simulated and analyzed, respectively. Moreover, Monte Carlo method is used to calculate the ranging mean and ranging deviation of each ranging distribution curve, which makes quantitative analysis possible. The results show that compared with the LED, the CFD can effectively suppress the effect caused by the change of angle and transmission power. However, it needs a narrower pulse width and a higher signal-to-noise ratio to maintain a higher ranging precision.

The correct way of splitting tools – Optimization of instrument design for measuring contact stress distribution

Contact stress on the tool has been measured with a split-tool apparatus that has a poor resolution of the stress distribution, and with photoelastic tools that cannot be used with real cutting parameters since the materials are too weak. This paper presents an improved split-tool design allowing continuous stress distribution dataset instead of discreet steps by using a tilted separation plane between the tool tip and the tool body. This paper optimizes the separation plane angle with 3D-FEM to minimize deflection.

Tilt to horizontal global solar irradiance conversion: An evaluation at high tilt angles and different orientations

Many transposition models have been proposed in the literature to convert solar irradiance on the horizontal plane to that on a tilted plane. The inverse process, i.e., the conversion from tilted to horizontal is investigated here based on six months of in-plane global solar irradiance measurements recorded on the roof of the Royal Meteorological Institute of Belgium's radiation tower in Uccle (Latitude 50.79°N, Longitude 4.35°E). Up to three pyranometers mounted on inclined planes of different tilts and orientations were involved in the inverse transposition process. Our results indicate that (1) the tilt to horizontal irradiance conversion is improved by using a multi-pyranometers approach and (2) the improvement from using an isotropic model to anisotropic models in the inverse transposition problem is not significant.

Evaluation of various procedures transposing global tilted irradiance to horizontal surface irradiance

Abstract. Many transposition models have been proposed in the literature to convert solar irradiance on the horizontal plane to that on a tilted plane. The inverse process, i.e. the conversion from tilted to horizontal is investigated here based upon seven months of in-plane global solar irradiance measurements recorded on the roof of the Royal Meteorological Institute of Belgium's radiation tower in Uccle (Longitude 4.35° E, Latitude 50.79° N). Up to three pyranometers mounted on inclined planes of different tilts and orientations were involved in the inverse transposition process. Our results indicate that (1) the tilt to horizontal irradiance conversion is improved when measurements from more than one tilted pyranometer are considered (i.e. by using a multi-pyranometer approach) and (2) the improvement from using an isotropic model to anisotropic models in the inverse transposition problem is not significant.

Performance of off-grid residential solar photovoltaic power systems using five solar tracking modes in Kunming, China

This paper compares the performance of a 2.02 kWp off-grid residential solar photovoltaic (PV) power system using PVSYST simulation software for a household in Kunming, Yunnan province, China. The monthly available solar energy; missing energy; array, final, and reference yields, performance ratio; and array capture and system losses were analyzed for five solar tracking modes: fixed tilted plane, seasonal tilt adjustment, horizontal axis tracking, vertical axis tracking, and dual axis tracking. Although there were some similar aspects across the five systems, minimum available solar energy (2461 kWh/y) and maximum missing energy (134.68 kWh/y) were obtained using the fixed tilted plane system (tilt angle = 25°, azimuth angle = 0°), whereas maximum available solar energy (3081 kWh/y) and minimum missing energy (48.53 kWh/y) in October were obtained using the dual axis tracking system. Average monthly performance ratio was maximal for the fixed tilted plane system (0.689), and minimal for the dual axis tracking system (0.596).

Delay-Encoded Harmonic Imaging (DE-HI) in Multiplane-Wave Compounding.

The development of ultrafast ultrasound imaging brings great opportunities to improve imaging technologies such as shear wave elastography and ultrafast Doppler imaging. In ultrafast imaging, several tilted plane or diverging wave images are coherently combined to form a compounded image, leading to trade-offs among image signal-to-noise ratio (SNR), resolution, and post-compounded frame rate. Multiplane wave (MW) imaging is proposed to solve this trade-off by encoding multiple plane waves with Hadamard matrix during one transmission event (i.e. pulse-echo event), to improve image SNR without sacrificing the resolution or frame rate. However, it suffers from stronger reverberation artifacts in B-mode images compared to standard plane wave compounding due to longer transmitted pulses. If harmonic imaging can be combined with MW imaging, the reverberation artifacts and other clutter noises such as sidelobes and multipath scattering clutters should be suppressed. The challenge, however, is that the Hadamard codes used in MW imaging cannot encode the 2nd harmonic component by inversing the pulse polarity. In this paper, we propose a delay-encoded harmonic imaging (DE-HI) technique to encode the 2nd harmonic with a one quarter period delay calculated at the transmit center frequency, rather than reversing the pulse polarity during multiplane wave emissions. Received DE-HI signals can then be decoded in the frequency domain to recover the signals as in single plane wave emissions, but mainly with improved SNR at the 2nd harmonic component instead of the fundamental component. DE-HI was tested experimentally with a point target, a B-mode imaging phantom, and in-vivo human liver imaging. Improvements in image contrast-to-noise ratio (CNR), spatial resolution, and lesion-signal-to-noise ratio ( l SNR) have been achieved compared to standard plane wave compounding, MW imaging, and standard harmonic imaging (maximal improvement of 116% on CNR and 115% on l SNR as compared to standard HI around 55 mm depth in the B-mode imaging phantom study). The potential high frame rate and the stability of encoding and decoding processes of DE-HI were also demonstrated, which made DE-HI promising for a wide spectrum of imaging applications.

Interferometric method for phase calibration in liquid crystal spatial light modulators using a self-generated diffraction-grating.

An auto-referenced interferometric method for calibrating phase modulation of parallel-aligned liquid crystal (PAL) spatial light modulators (SLM) is described. The method is experimentally straightforward, robust, and requires solely of a collimated beam, with no need of additional optics. This method uses the SLM itself to create a tilted plane wave and a reference wave which mutually interfere. These waves are codified by means of a binary diffraction grating and a uniformly distributed gray level area (piston) into the SLM surface. Phase shift for each gray level addressed to the piston section can then be evaluated. Phase modulation on the SLM can also be retrieved with the proposed method over spatially resolved portions of the surface. Phase information obtained with this novel method is compared to other well established calibration procedures, requiring extra elements and more elaborated optical set-ups. The results show a good agreement with previous methods. The advantages of the new method include high mechanical stability, faster performance, and a significantly easier practical implementation.

A spatial algorithm to reduce phase wraps from two dimensional signals in fringe projection profilometry

In this paper, we present a novel algorithm to reduce the number of phase wraps in two dimensional signals in fringe projection profilometry. The technique operates in the spatial domain, and achieves a significant computational saving with regard to existing methods based on frequency shifting. The method works by estimating the modes of the first differences distribution in each axial direction. These are used to generate a tilted plane, which is subtracted from the entire phase map. Finally, the result is re-wrapped to obtain a phase map with fewer wraps. The method may be able to completely eliminate the phase wraps in many cases, or can achieve a significant phase wrap reduction that helps the subsequent unwrapping of the signal. The algorithm has been exhaustively tested across a large number of real and simulated signals, showing similar results compared to approaches operating in the frequency domain, but at significantly lower running times.

Validation of an operational product to determine L1 to Earth propagation time delays

AbstractWe describe the development and validation of an operational space weather tool to forecast propagation delay times between L1 and Earth using the Weimer and King (2008) tilted phase front technique. A simple flat plane convection delay method is currently used by the NOAA Space Weather Prediction Center (SWPC) to propagate the solar wind from a monitoring satellite located at L1 to a point upstream of the magnetosphere. This technique assumes that all observed solar wind discontinuities, such as interplanetary shocks and interplanetary coronal mass ejection boundaries, are in a flat plane perpendicular to the Sun‐Earth line traveling in the GSE X direction at the observed solar wind velocity. In reality, these phase plane fronts can have significantly tilted orientations, and by relying on a ballistic propagation method, delay time errors of ±15 min are common. In principle, the propagation time delay product presented here should more accurately predict L1 to Earth transit times by taking these tilted phase plane fronts into account. This algorithm, which is based on the work of Weimer and King (2008), is currently running in real time in test mode at SWPC as part of the SWPC test bed. We discuss the current algorithm performance, and via our detailed validation study, show that there is no significant difference between the two propagation methods when run in a real‐time operational environment.

Development of Site Specific Optimal Tilt Angle Model for Fixed Tilted Plane PV Installation ın Akwa Ibom State, Nigeria

Photovoltaic (PV) panels’ orientation (azimuth angle) and tilt angle significantly affect the energy output of PV power plants. The reason is because the photovoltaic panels produce more electric energy when their surfaces are perpendicular to the sun's rays. Researchers have developed models for estimating the optimal tilt angle for any given location across the globe. In this paper, a site specific model is developed for more accurate estimation of the optimal tilt angle for fixed-tilt angle PV installations at the Ibom E-Library in Uyo metropolis, Akwa state of Nigeria. The solar radiation data used for the study was obtained from the National Aeronautics and Space Administration Surface meteorology and Solar Energy (NASA SSE) website. PVsyst simulation software was used to perform the transposition of the global radiation on horizontal plane to tilted plane. For the location with latitude of 5.123° the existing model estimated the optimal tilt angle as 7.16035° whereas, the site-specific model estimated 11.5° for the optimal tilt angle. The model has prediction accuracy of 99.77% and root mean square error of 0.002567. The optimal tilt angle model can be employed for fixed tilted plane PV installations in the nearby locations.

Multiplane wave imaging increases signal-to-noise ratio in ultrafast ultrasound imaging

Ultrafast imaging using plane or diverging waves has recently enabled new ultrasound imaging modes with improved sensitivity and very high frame rates. Some of these new imaging modalities include shear wave elastography, ultrafast Doppler, ultrafast contrast-enhanced imaging and functional ultrasound imaging. Even though ultrafast imaging already encounters clinical success, increasing even more its penetration depth and signal-to-noise ratio for dedicated applications would be valuable.Ultrafast imaging relies on the coherent compounding of backscattered echoes resulting from successive tilted plane waves emissions; this produces high-resolution ultrasound images with a trade-off between final frame rate, contrast and resolution. In this work, we introduce multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate. This method relies on the successive transmissions of multiple plane waves with differently coded amplitudes and emission angles in a single transmit event. Data from each single plane wave of increased amplitude can then be obtained, by recombining the received data of successive events with the proper coefficients.The benefits of multiplane wave for B-mode, shear wave elastography and ultrafast Doppler imaging are experimentally demonstrated. Multiplane wave with 4 plane waves emissions yields a 5.8 ± 0.5 dB increase in signal-to-noise ratio and approximately 10 mm in penetration in a calibrated ultrasound phantom (0.7 d MHz−1 cm−1). In shear wave elastography, the same multiplane wave configuration yields a 2.07 ± 0.05 fold reduction of the particle velocity standard deviation and a two-fold reduction of the shear wave velocity maps standard deviation. In functional ultrasound imaging, the mapping of cerebral blood volume results in a 3 to 6 dB increase of the contrast-to-noise ratio in deep structures of the rodent brain.

3-D ultrafast Doppler imaging applied to the noninvasive mapping of blood vessels in vivo.

Ultrafast Doppler imaging was introduced as a technique to quantify blood flow in an entire 2-D field of view, expanding the field of application of ultrasound imaging to the highly sensitive anatomical and functional mapping of blood vessels. We have recently developed 3-D ultrafast ultrasound imaging, a technique that can produce thousands of ultrasound volumes per second, based on a 3-D plane and diverging wave emissions, and demonstrated its clinical feasibility in human subjects in vivo. In this study, we show that noninvasive 3-D ultrafast power Doppler, pulsed Doppler, and color Doppler imaging can be used to perform imaging of blood vessels in humans when using coherent compounding of 3-D tilted plane waves. A customized, programmable, 1024-channel ultrasound system was designed to perform 3-D ultrafast imaging. Using a 32 × 32, 3-MHz matrix phased array (Vermon, Tours, France), volumes were beamformed by coherently compounding successive tilted plane wave emissions. Doppler processing was then applied in a voxel-wise fashion. The proof of principle of 3-D ultrafast power Doppler imaging was first performed by imaging Tygon tubes of various diameters, and in vivo feasibility was demonstrated by imaging small vessels in the human thyroid. Simultaneous 3-D color and pulsed Doppler imaging using compounded emissions were also applied in the carotid artery and the jugular vein in one healthy volunteer.

Estimation of Solar Irradiation on Inclined Surface Based on Web Databases

Abstract Estimation of Global Tilted Irradiation (GTI) is a key to performance assessment of typical solar systems since they usually employ tilted photovoltaic (PV) modules or collectors. Numerous solar radiation databases can deliver irradiation values both on horizontal and tilted plane, however they are validated mostly with horizontal-plane ground measurements. In this paper we have compared GTI estimates retrieved from five Internet databases with results of measurements at two PV systems located in Poland. Our work shows that in spite of good agreement in annual scale, there is a tendency to underestimate GTI in summer and overestimate in winter, when PV modules can receive less than a half of expected irradiation. The latter issue affects sizing of PV system components and implies a correction needed to achieve all-year long operation.

Forced rotation of nanograting in glass by pulse-front tilted femtosecond laser direct writing.

Femtosecond pulse laser with tilted intensity front demonstrates the capability of rotating the writing of nanograting in glass in 3D space. Other than the light polarization, this phenomenon is also associated with the quill-writing effect, which depends on the correlation between the sample movement and the pulse front tilt. This is because a pondermotive force, perpendicular to the tilted intensity plane, can push the excited electron plasma forward towards the pulse front. This behavior further tilts the electrical field plane and eventually result in a forced rotation of nanograting in 3D space.

Mechanical analysis of a natural example of onland gravity gliding: The role of river incision and deposition

AbstractGravity gliding implies rigid translation of a body down a slope where displacements are parallel to a tilted detachment plane. Although large‐scale gravity gliding is commonly observed offshore, under conditions of high fluid overpressure and abundant upslope sedimentary supply, its occurrence on land is debated. We investigate the mechanical feasibility of such a process as well as the role of fluvial incision and sedimentation down the slope in the initiation of the gliding. We use a two‐dimensional (2‐D) finite element model combined with a 2‐D failure analysis approach. The numerical models simulate the deformation and provide quantitative estimates of the failure criteria at the head and toe of the overburden. Analytical solutions approximate the numerical results by taking into account the fluvial incision and sedimentation, the internal friction angle, and the thickness and length of the overburden. Our models are based on a field example in the Andean foothills of Argentina, where gravity gliding of a 1000 m thick section is suspected above a crustal‐scale anticline. The incision and sedimentation reduce and strengthen, respectively, the downslope resistance to contractional failure. The critical slope at which the gliding is initiated is reduced by fluvial incision and increased by sedimentation. We show that tectonic uplift may lead to large‐scale gravity gliding on land where the overburden thickness is less than 2000 m. Incision facilitates and localizes the frontal shortening. Incision greater than 1000 m may trigger gliding for overburden up to 4000 m thick, while sedimentation thicker than 1000 m inhibits gliding. These results show that thin‐skinned onland gravity gliding could be common in tectonically active regions where incision is important.

Switching of Conducting Planes by Partial Dimer Formation in IrTe2

Single-crystal X-ray diffraction was employed to study the structural-electronic phase transition of IrTe$_2$ at approximately 270 K. The low-temperature structure was found to be a triclinic (space group $P\bar{1}$) characterized by the partial formation of Ir$_2$ dimers in the triangular lattice of IrTe$_2$, resulting in a structural modulation with a wave vector of ${\bf q} = (1/5, 0, -1/5)$. First-principles band calculations demonstrate that tilted two-dimensional Fermi surfaces emerge in the triclinic phase, suggesting that switching of the conducting planes occurs from the basal plane of the trigonal IrTe$_2$ to the tilted plane normal to ${\bf q}$ of the triclinic IrTe$_2$.

Hemimandibular Hyperplasia

Hemimandibular hyperplasia (HH) is a developmental asymmetry characterized by three-dimensional enlargement of one half of the mandible. The hyperplastic side usually involves the condyle, condylar neck, ramus, and body, with the anomaly terminating abruptly at the symphysis. The malformation results in the clinical presentation of ipsilateral enlargement of the mandible and tilted occlusal plane, associated with a deviated chin to the contralateral side. Since the first case report of HH in the English literature in 1836, various terminology and classifications were used. In this study, the authors classified the patients into typical and atypical types of HH on the basis of clinical and radiologic observations in an effort to achieve a simplified and efficient surgical management on the basis of the severity of deformity. Accordingly, surgical treatments are designed respectively on the basis of the authors' classification and treatment algorithm. In addition, in view of potential complications arising from condylectomy, none of the patients had undergone condylectomy as part of the surgical treatment. The authors present their experience on the basis of this proposed classification and treatment algorithm with functional and aesthetic outcomes as the end points of this study.

Holographic Image Projection on Tilted Planes by Phase-Only Computer Generated Hologram Using Fractional Fourier Transformation

We propose a new method to compute the phase-only computer-generated hologram (CGH) that can modulate an image on a tilted plane. We used the fractional Fourier transformation to compute light propagation between the hologram plane and the tilted plane. The phase-only hologram was obtained by an iterative algorithm. We proposed a method to calculate the inverse optical propagation from the hologram plane to a tilted plane by coordinate rotation and a simple interpolation in the Fourier domain. The experimental results show that the projected image on the tilted plane can be reconstructed by a phase-only hologram generated by our iterative algorithm. We also show that the quality of the projected image on the tilted plane is better than the image projected by the phase hologram generated by traditional method.

The formation of Local Group planes of galaxies

The confinement of most satellite galaxies in the Local Group to thin planes presents a challenge to the theory of hierarchical galaxy clustering. The PAndAS collaboration has identified a particularly thin configuration with kinematic coherence among companions of M31 and there have been long standing claims that the dwarf companions to the Milky Way lie in a plane roughly orthogonal to the disk of our galaxy. This discussion investigates the possible origins of four Local Group planes: the plane similar, but not identical to that identified by PAndAS, an adjacent slightly tilted plane, and two planes near the Milky Way: one with nearer galaxies and the other with more distant ones. Plausible orbits are found by using a combination of Numerical Action methods and a backward in time integration procedure. For M31, M33, IC10, and LeoI, solutions are found that are consistent with measurements of their proper motions. For galaxies in planes, there must be commonalities in their proper motions, and this constraint greatly limits the number of physically plausible solutions. Key to the formation of the planar structures has been the evacuation of the Local Void and consequent build-up of the Local Sheet, a wall of this void. Most of the M31 companion galaxies were born in early-forming filamentary or sheet-like substrata that chased M31 out of the void. M31 is a moving target because of its attraction toward the Milky Way, and the result has been alignments stretched toward our galaxy. In the case of the configuration around the Milky Way, it appears that our galaxy was in a three-way competition for companions with M31 and Centaurus A. Only those within a modest band fell our way. The Milky Ways' attraction toward the Virgo Cluster resulted in alignments along the Milky Way-Virgo Cluster line.

Kepler finds system with planets sharing extremely tilted orbital plane

Kepler finds system with planets sharing extremely tilted orbital plane