Obliquity Research Articles

Long-Range 3D Reconstruction Based on Flexible Configuration Stereo Vision Using Multiple Aerial Robots

Aerial robots, or unmanned aerial vehicles (UAVs), are widely used in 3D reconstruction tasks employing a wide range of sensors. In this work, we explore the use of wide baseline and non-parallel stereo vision for fast and movement-efficient long-range 3D reconstruction with multiple aerial robots. Each viewpoint of the stereo vision system is distributed on separate aerial robots, facilitating the adjustment of various parameters, including baseline length, configuration axis, and inward yaw tilt angle. Additionally, multiple aerial robots with different sets of parameters can be used simultaneously, including the use of multiple baselines, which allows for 3D monitoring at various depth ranges simultaneously, and the combined use of horizontal and vertical stereo, which improves the quality and completeness of depth estimation. Depth estimation at a distance of up to 400 m with less than 10% error using only 10 m of active flight distance is demonstrated in the simulation. Additionally, estimation of a distance of up to 100 m with flight distance of up to 10 m on the vertical axis and horizontal axis is demonstrated in an outdoor mapping experiment using the developed prototype UAVs.

Study on Impoundment Deformation Characteristics and Crack of High Core Rockfill Dam Based on Inversion Parameters

In the numerical simulation of earth-rock dam, accurate and reliable mechanical parameters of the dam material are the important basis for dam deformation predictions and dam safety evaluations. Based on the deformation monitoring data of Luding core wall rockfill dam, the rheological parameters of rockfill and core wall materials are inverted in this paper. Combined with the actual filling and impoundment process of the dam, the numerical simulation is carried out, and the stress deformation and differential settlement of the dam after completion and impoundment are analyzed. The results showed that the stress deformation results of the dam based on the inversion parameters were in good agreement with the actual deformation. The horizontal displacement, settlement, and principal stress of the dam during the completion period were symmetrically distributed along the core wall. The maximum horizontal displacement occurred at the main dam on both sides of the core wall and the upstream and downstream dam slopes, and the maximum settlement occurred in the middle of the core wall. During the impoundment period, under the action of reservoir water pressure and upstream rockfill wetting deformation, the deformation and stress of the dam body no longer met the symmetrical distribution law, and the maximum horizontal displacement of the dam body during the impoundment period was located at 2/3 of the upstream dam slope. The maximum settlement of the dam body was located at 1/2 of the dam height. The maximum principal stress on the upstream side of the core wall was located on the left side of the bottom of the core wall, and the minimum principal stress was also located on the left side of the bottom of the core wall. The simulation results of the deformation and stress met the general law of earth-rock dam engineering. During the completion period, the deformation inclination of the dam crest was less than 1%. During the impoundment period, the deformation inclination of the dam crest area increased due to the wetting deformation of the upstream rockfill material. At the same time, the deformation inclination of the dam crest axis was larger than that of the upstream and downstream sides, and the deformation inclination of the dam crest at the middle of the valley was the largest, but it did not exceed 3%, that is, there would be no longitudinal cracks, which is consistent with the actual situation. The research results can better predict the stress deformation and crack of the dam body, and provide important support for dam safety evaluations.

Determination and Analysis of Working Diameters and Working Angle of the Torus Cutter Blade in Multi-axis Machining in the Aspect of Tool Wear

The aim of this study is to provide a theoretical and experimental analysis of the multi-axis milling process by the torus milling cutter of nickel-based superalloy parts in terms of surface quality and tool wear. In the analytical part, using, among other things, matrix calculus and trigonometric relationships, mathematical models were developed to describe the relationships between the tool axis orientation and the geometric parameters of the cutting layer at the contact point. On this basis, mathematical relationships for contact diameter and effective diameter were derived. The basis for these considerations is the very rarely considered working angle of the cutter blade. In part of the experimental study, machining tests were carried out for selected kinematic variants of multi-axis cutting. Based on the results obtained, it was found that as the tool axis inclination angle increases, the contact diameter increases. The effective diameter at the upper characteristic point of the cutting layer increases up to a certain angle of inclination, after which it begins to decrease. The rotational angle of the tool axis does not affect any of the diameters, but it does affect the displacement of the contact point, the values of the working angle of the tool blade and the feed-related component decrease. The result of this displacement is a change from climb milling to conventional milling, which has significantly degraded surface quality and tool life. The best results of the machining test were obtained when only the angle of inclination of the tool axis was used. It was concluded that the parameter tool blade working angle can be a control variable in a multi-axis milling process and has a major impact on the physical aspects of the cutting process.

Pair correlations of the easy magnetisation axes of superparamagnetic nanoparticles in a ferrofluid/ferrocomposite.

The widespread use of magnetic nanoparticles in modern technologies and medical applications highlights the need for reliable theoretical models that can predict their physical properties. The pair correlation function of two randomly selected superparamagnetic nanoparticles in a ferrofluid/ferrocomposite is studied to depict the joint probability density of the easy magnetisation axes across the planes of parameters of major importance; these are the interaction of ferroparticles with an external magnetic field, the energy of magnetic anisotropy inside the superparamagnetic nanoparticle, and the interparticle magnetic dipole-dipole interaction. Assuming the rotational symmetry of the system, we come to the conclusion that the pair correlations of interest are dependent only on the polar angles, determining the inclinations of the ferroparticle easy axes from the direction of an external magnetic field. The dimer configuration, where two ferroparticles are in close contact along a magnetic field with their easy magnetisation axes aligned, is the most probable. This configuration becomes more pronounced with increasing anisotropy energy, dipolar coupling constant, and external magnetic field.

Titan’s Atmospheric Albedo Asymmetry and Seasonal Variability Observed through the Cassini Imaging Science Subsystem

Using images from Cassini, we analyzed the north–south albedo asymmetry that has been observed in the atmosphere of Saturn’s moon, Titan. Suitable images from the Cassini Imaging Science Subsystem taken at 889 nm spanned from 2004 to 2017—around half of a Titan year—and revealed seasonal changes in the characteristics and orientation of the north–south asymmetry boundary. Such circumglobal features provide insight into the dynamics and circulation of the atmosphere more broadly. The albedo asymmetry has been observed to reverse for part of the Titan year, inverting the brighter and darker hemispheres; we also observed this inversion, along with the formation of additional banding briefly during the transition (around 2014–2016). A tilt in the rotation axis of Titan’s atmosphere with respect to the solid body rotation has previously been noted. Using robust edge-detection techniques, we likewise identified a tilt offset of a few degrees in the albedo transition boundaries. The azimuth of this tilt axis remained roughly fixed in inertial space, with some smaller possible seasonal fluctuations around the fixed direction noted.

Research of the elastic properties of a vehicle tire with an tilting wheel rotation axis

The purpose of the study is to develop computational and experimental methods for determining the normal, longitudinal and lateral stiffness of a vehicle tire with an inclined rotation wheel axis. Dimensionless correction factors were obtained to adjust the tire stiffness along the corresponding coordinate when the wheel rotation axis is tilted. It has been established that when the wheel rotation axis is tilted, the tire stiffness changes along different coordinates in different ways. It has been determined that the normal and longitudinal tire stiffness when the wheel rotation axis is tilted always decreases, regardless of the tilt direction. A change in the lateral tire stiffness when the wheel rotation axis is tilted can occur either in the direction of decrease or increase, depending on the combination of the tilt direction and the vector of the wheel lateral force. Keywords vehicle support wheel, rotation axis tilt, tire elastic properties, methods for determining

Correction of Anterior Crossbite, Using Removable Appliances in Mixed Dentition: 5-Year Follow-Up

The anterior crossbite (ACB) is a malocclusion where the upper anterior teeth are occluding lingually with respect to the lower anterior teeth. Moyers describes anterior crossbites as dental malocclusions resulting from abnormal axial inclinations of the anterior teeth. This type of malocclusion can be dental, functional or skeletal and can occur in the primary, mixed and second dentition. Diagnosis is made using diagnostic aids. While the treatment was carried out through interceptive orthodontics, with the use of different removable appliances. The objective of the study is to present the diagnosis and treatment for 5 years with the use of removable appliances. The results were favorable, being able to uncross the bite in 4 months, it was maintained throughout the dental replacement. One of the conclusions reached is that the treatment time is slightly longer since the use of preventive and interceptive orthodontics takes more time because these treatments are performed during the growth of the patients.

Enhancing Wind Farm Performance through Axial Induction and Tilt Control: Insights from Wind Tunnel Experiments

Static axial induction control and tilt control are two strategies that have the potential to increase power production in wind farms, mitigating wake effects and increasing the available power for downstream turbines. In this study, wind tunnel experiments are performed to evaluate the efficiency of these two techniques. First, the axial induction of upstream turbines in wind farms comprising two, three, and five turbines is modified through the tip-speed ratio. This strategy is found to be ineffective in increasing power extraction. Next, the power extraction and flow through a two-turbine wind farm are evaluated, considering different tilt angles for the upstream turbine, under two levels of incoming flow turbulence intensities and turbine spacing distances. It is shown that forward tilting increases the overall power extraction by deflecting the wake downwards and promoting the entrainment of high-speed fluid in the upper shear layer, regardless of the turbine spacing distance and turbulence intensity level. Also, the wake is seen to recover faster due to the increased shear between the wake and the outer flow. Tilting a turbine backward deflects the wake upwards and pulls low-speed flow from under the turbine into the wake space, increasing the available power for downstream turbines, but it is not enough to increase global power extraction. Moreover, since the wake deflection under backward tilting is not limited by ground blockage, it leads to larger secondary steering compared with forward tilting. Finally, it is demonstrated that the secondary steering of the downstream turbine’s wake influences the flow encountered by a turbine positioned farther downstream.

Analysis of Adaptive Individual Pitch Control Schemes for Blade Fatigue Load Reduction on a 15 MW Wind Turbine

Individual pitch control (IPC) is a method to mitigate periodic blade loads in wind turbines, and it is typically implemented using the multi-blade coordinate (MBC) transform, which converts the blade load measurements from a rotating frame into the non-rotating tilt axis and yaw axis. Previous studies have shown that by including an additional tuning parameter in the MBC, the azimuth offset reduces the coupling between non-rotating axes, allowing for higher performance levels for diagonal controller structures. In these studies, the decentralized control of IPC was composed of two identical integral controllers. This work analyzes and compares the improvement that the azimuth offset can provide in different adaptive gain scheduling IPCs where the diagonal controllers can have integral or proportional action with different gains. They are applied to a 15 MW wind turbine simulated with OpenFAST v3.5 software. The controller parameter tuning is addressed as an optimization that reduces blade fatigue load based on the damage equivalent load (DEL) and is resolved through genetic algorithms. Simulations show that only using different controller gains in IPC does not provide significant improvements; however, including azimuth offset in the optimal IPC schemes with integral controllers allows for the greatest DEL reduction with a lower actuator effort.

Influence of the modified Dunn procedure on the spine–pelvis relationship in children with severe slipped capital femoral epiphysis

BACKGROUND: Slipped capital femoral epiphysis (SCFE) is one of the most severe hip joint diseases in children. It is characterized by the development of unilateral or bilateral deformity of the proximal femoral epimetaphysis of varying degrees. The pronounced deformity of the femoral component of the affected joint leads to pelvic retroversion, decreased lumbar lordosis, increased thoracic kyphosis (TK), and formation of type I (hypolordotic) vertical posture according to the Roussouly classification, contributing to degenerative and dystrophic processes in the lumbosacral spine. At present, no data in the literature present the effect of surgical treatment on frontal and sagittal spine–pelvis relationships in the patients examined.
 AIM:To performacomparative radiological evaluation of the sagittal spine–pelvis relationship in children with severe SCFE before and after the modified Dunn procedure.
 MATERIALS AND METHODS:The study included 30 patients (30 hip joints) aged 14–18 years with severe SCFE characterized byaposterior epiphysis displacement of 60° and downward of no more than 10° in one of the joints and no displacement (preslip stage) in the other. All children underwent the modified Dunn procedure on one side and fixation of the epiphysis of the femoral head withacannulated screw on the other side. Before and after surgery, the patients underwent clinical and radiologic examinations. Standing radiographs were used to evaluate lumbar lordosis, TK, pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and sagittal vertical axis (SVA). The obtained data were analyzed statistically.
 RESULTS:At the examination 3–3.5 years after the abovementioned interventions,apronounced increase was noted in the mean PI value, which began to correspond to type III (harmonious) of upright posture according to the Roussouly classification.Achange was noted in the mean values of positional indices PT (decreased) and SS (increased), and pelvic retroversion disappeared. The mean global lumbar lordosis (GLL) and lumbar lordosis increased, which led toadecrease in TK and the mean value of TK. All clinical observations showedasignificant decrease in the mean global sagittal balance index (the sagittal vertical axis (SVA)) and absence of torso imbalance.
 CONCLUSIONS:After performing the modified Dunn procedure on the one side and fixation of the epiphysis of the femoral head withascrew on the other side, children with severe SCFE demonstrated improvements in all the studied indices of sagittal spine–pelvis ratios. Consequently, the type of vertical posture according to the Roussouly classification changes from type I (hypolordotic) to type III (harmonious), and the probability of degenerative and dystrophic process development in the lumbosacral spine decreases.

Core shift controls grain boundary energy scaling in Cu and Al

Grain boundary energies in different elements are correlated. The proportional scaling constants relating the energies of crystallography-equivalent boundaries in any two f.c.c. elements are nearly constant, with the notable exception of aluminum where these constants are known to vary significantly. However, the origins of the exceptional behavior of aluminum are not understood. Previously, we reported that for fcc metals there is a preference for tilt boundaries to shift their tilt axis across the (11¯0) plane towards [112] and to ultimately form low energy [112] core shifted boundaries (CSBs). By comparing grain boundary energies in copper and aluminum with different tilt axes in (11¯0) plane, we now report the existence of a well-defined scaling behavior for the case of low angle boundaries. In contrast, the scaling constant for high angle boundaries is essentially fixed regardless of their tilt axis shift. This results in a gradual change in the scaling constants from low angle to high angle boundaries, which is responsible for the apparent exceptional scaling behavior found in aluminum. An analysis of structure evolution during core shifting points to the significance of boundary-core dissociation, a form of correlated relaxation of individual atoms at boundaries, in controlling the scaling of boundary energies.

Radiographic predictors of reaching minimal clinically important difference following lumbar fusion surgery in patients with degenerative lumbar spondylolisthesis.

The present study aimed to (1) compare sagittal alignment between patients with degenerative lumbar spondylolisthesis (DLS) who reached or missed the minimal clinically important difference (MCID) for clinical outcomes following lumbar fusion surgery (LFS) and (2) identify radiographic predictors associated with MCID achievement in DLS patients. A total of 91 single-level DLS patients who underwent LFS and had a minimum of 1-year follow-up were enrolled in this study. The assessed radiographic parameters included thoracic kyphosis, lumbar lordosis (LL), segmental lumbar lordosis (SLL), slip percentage, sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), and sagittal vertical axis. Changes in radiographic parameters were determined by subtracting the preoperative value from the final follow-up measurement. Clinical outcomes were assessed using the Oswestry Disability Index (ODI) and the visual analog scale (VAS) for both back and leg pain. MCID values were set at 10 points for ODI, 2.1 points for VAS back pain, and 2.8 points for VAS leg pain. Patients were assigned to the reached MCID (rMCID) and missed MCID (mMCID) groups based on the postoperative (post-op) recovery of clinical outcomes. At the last follow-up, 68.1% (62/91), 72.5% (66/91), and 76.9% (70/91) of patients reached MCID for ODI, VAS back pain, and VAS leg pain, respectively. Concerning ODI, the rMCID group exhibited higher post-op LL (47.93° vs. 42.95°, P = 0.044), higher post-op SLL (17.08° vs. 14.41°, P = 0.032), higher post-op SS (34.46° vs. 30.63°, P = 0.027), higher ∆LL (5.90° vs. 2.44°, P = 0.017), higher ∆SLL (4.63° vs. - 1.03°, P < 0.001), higher ∆SS (4.76° vs. 1.23°, P = 0.002), lower post-op PT/PI (36.95% vs. 42.01%, P = 0.049), lower ∆PT (- 3.71° vs. 1.05°, P < 0.001), lower ∆PT/PI (- 7.45% vs. 1.97%, P < 0.001), and lower ∆PI-LL (- 5.43° vs. - 3.71°, P = 0.011) than the mMCID group. Regarding VAS back pain, the rMCID group showed higher post-op SLL (17.06° vs. 14.05°, P = 0.021), higher post-op SS (34.34° vs. 30.33°, P = 0.027), higher ∆SLL (3.93° vs. - 0.09°, P < 0.001), and lower ∆PT (- 2.91° vs. - 0.30°, P = 0.039) than the mMCID group. For VAS leg pain, higher ∆SLL (3.55° vs. 0.41°, P = 0.003) was observed in the rMCID group than in the mMCID group. Multivariate logistic regression analysis revealed that higher ∆SLL, higher ∆SS, and higher post-op SS were independent predictors for the achievement of MCID in patients with DLS. DLS patients who reached MCID following LFS demonstrated improved post-op spinopelvic alignment. Higher ∆SLL, higher ∆SS, and higher post-op SS were the critical parameters associated with MCID achievement in patients with DLS.

Short-segment spinal fusion for chronic low back pain with bone marrow edema adjacent to the vertebral endplate in adult spinal deformity.

Corrective long spinal fusion is a widely accepted surgical method for patients with adult spinal deformities. However, instrumented long fusion is associated with a significant risk of complications. Therefore, we aimed to assess the success of short-segment spinal fusion, particularly for bone marrow edema (BME) adjacent to the vertebral endplate, in patients with low back pain (LBP) and spinal deformity. A prospective study was performed at multiple hospitals wherein we monitored patients with spinal deformities and accompanying LBP. Patients aged ≥ 50years with a minimum LBP severity score of 40mm on the visual analog scale (VAS) were included in the study. We also included patients with lumbar BME on magnetic resonance imaging. Short spinal fusion was performed on segments with BME. Clinical evaluations of LBP on VAS and Oswestry Disability Index (ODI), and radiological parameters for sagittal vertical axis (SVA), pelvic incidence (PI), lumbar lordosis (LL) and pelvic tilt (PT) were carried out. Overall, 35 patients (22 men and 13 women), with a mean age of 66.7years and a mean follow-up period of 32months, were included in the study. The mean VAS and ODI scores were 72.4mm and 49.0% before surgery and 25.5mm and 29.9% at the final follow-up, respectively; these parameters significantly improved after surgery. The SVA, PI-LL, and PT scores were 70.1mm, 20.9°, and 22.8° before surgery and 85.4mm, 13.8°, and 22.7° at the final follow-up, respectively. The spinal alignment parameters did not change significantly after surgery. Short-segment spinal fusion is effective for treating LBP and spinal deformity with BME adjacent to the vertebral endplate without spinal correction.

Detecting active latitudes of Sun-like stars using asteroseismic a-coefficients

Aims. We introduce a framework to measure the asphericity of Sun-like stars using a1, a2, and a4 coefficients and constrain their latitudes of magnetic activity. Methods. We evaluated systematic errors on the inferred coefficients in function of key physical and seismic parameters (inclination of rotation axis, average rotation, height-to-noise ratio of peaks in power spectrum). The measured a-coefficients account for rotational oblateness and the effect of surface magnetic activity. We used a simple model that assumes a single latitudinal band of activity. Results. Using solar SOHO, VIRGO, and SPM data, we demonstrate the capability of the method to detect the mean active latitude and its intensity changes between 1999 and 2002 (maximum of activity) and 2006 and 2009 (minimum of activity). We further applied the method to study the solar-analogue stars 16 Cyg A and B using Kepler observations. In 16 Cyg A, we detected an equatorial band of activity exhibiting an intensity that could be comparable to that of the Sun. However, 16 Cyg B exhibits a bimodality in a4 that is challenging to explain. We suggest that this could be a manifestation of the transition between a quiet and an active phase of activity. Validating or invalidating this hypothesis may require new observations.

Outcomes of Presurgical Nasoalveolar Molding using Modified Nostril Retainers in Patients with Unilateral Cleft Lip and Palate at an Average Follow-up of 2 Years.

Presurgical nasoalveolar molding (PNAM) using a modified nostril retainer is a new treatment approach. This study aimed to evaluate the outcomes of early nasal molding using this approach with an average follow-up of 2 years in patients with severe unilateral cleft lip and palate. This retrospective study included 18 patients with unilateral cleft lip and palate without genetic syndromes who underwent PNAM with modified nostril retainers. The Grayson technique was employed with an intraoral plate to approximate cleft segments. Nasal molding was initiated before reducing the cleft width to 5 mm. Measurements, including alar base height ratio (ABHR), nasal floor width ratio (NFWR), columellar length ratio (CLR), columellar angle (CA), and nostril axis inclination on the cleft and non-cleft sides (NAI-C and NAI-NC, respectively), were calculated from standard photographs taken before PNAM (T1), after PNAM (T2), after an average of 1.81 months post-surgery (T3), and after an average of 2.2 years after T3 (T4). Pairwise comparisons of values at the four time points were conducted. NFWR, CLR, CA, NAI-C and NAI-NC significantly increased after PNAM (p<0.05). However, no significant change was observed in ABHR (p>0.05) from T1 to T2. These outcomes were maintained at T4, and no patient developed a mega nostril. The use of a modified nostril retainer for nasal molding appears to provide stability during the high probability of relapse reported in the literature.

Two‐dimensional anisotropic acoustic wave modelling using the support operator method

AbstractWe developed an algorithm to simulate two‐dimensional frequency domain acoustic‐wave response in a transversely isotropic medium with a tilted symmetry axis. The algorithm employs a support operator finite‐difference method for modelling. This method constructs a nine‐point stencil finite‐difference scheme for second‐order elliptic equations for generalized anisotropic physical properties. The medium's properties are described as P‐wave velocity on the symmetric axis, density, Thomsen's anisotropic parameters (epsilon and delta) and the tilt angle. The benchmarking analysis of the modelled amplitude is illustrated using an isotropic whole‐space model. Several synthetic experiments are conducted to evaluate the accuracy of the scheme for anisotropic models. The results suggest that the developed algorithm simulates the P‐wave solution and the fictitious S‐wave mode as reported in the literature. Simulation for a heterogeneous model with a spatially varying tilt angle of the medium symmetry axis is performed to ascertain the algorithm's robustness. The outcomes of the numerical experiments demonstrate that the developed algorithm can accurately simulate the frequency domain response of acoustic waves in the tilted anisotropic media.

Trunk orthosis with joints providing resistive force improves dynamic sagittal alignment in postoperative patients with lumbar spinal stenosis

This study aimed to determine whether a trunk orthosis with joints providing resistive force (TORF) modifies sagittal malalignment during level walking in patients with lumbar spinal stenosis (LSS). Fifteen patients, 6 months after undergoing surgery for LSS, performed level walking at a self-selected speed while wearing a TORF. Dynamic sagittal alignment, including sagittal vertical axis, lumbar lordosis, and pelvic tilt, and spatiotemporal data as well as lower limb kinematic and kinetic data were recorded using a three-dimensional motion analysis system and six force plates. Statistical analysis was performed to compare these data with and without the TORF, respectively. Compared to the condition without the TORF, the use of the TORF significantly decreased positive sagittal vertical axis (p < 0.05) and increased the lumbar lordosis and pelvic tilt (p < 0.05). Peak hip flexion angle and extension moment during loading response (LR) significantly increased (p < 0.05), and peak hip extension angle and flexion moment during PS statistically decreased (p < 0.05). There was no difference in spatiotemporal data between the two conditions. Our findings suggest that TORF may modify the dynamic sagittal global alignment and lower limb kinematic and kinetics in postoperative LSS patients during level walking.

Tidal Dissipation Regimes among the Short-period Exoplanets

The efficiency of tidal dissipation provides a zeroth-order link to a planet’s physical properties. For super-Earth and sub-Neptune planets in the range R ⊕ ≲ R p ≲ 4R ⊕, particularly efficient dissipation (i.e., low tidal quality factors) may signify terrestrial-like planets capable of maintaining rigid crustal features. Here, we explore global constraints on planetary tidal quality factors using a population of planets in multiple-planet systems whose orbital and physical properties indicate susceptibility to capture into secular spin–orbit resonances. Planets participating in secular spin–orbit resonance can maintain large axial tilts and significantly enhanced heating from obliquity tides. When obliquity tides are sufficiently strong, planets in low-order mean-motion resonances can experience resonant repulsion (period ratio increase). The observed distribution of period ratios among transiting planet pairs may thus depend nontrivially on the underlying planetary structures. We model the action of resonant repulsion and demonstrate that the observed distribution of period ratios near the 2:1 and 3:2 commensurabilities implies Q values spanning from Q ≈ 101–107 and peaking at Q ≈ 106. This range includes the expected range in which super-Earth and sub-Neptune planets dissipate (Q ≈ 103–104). This work serves as a proof of concept for a method of assessing the presence of two dissipation regimes, and we estimate the number of additional multitransiting planetary systems needed to place any bimodality in the distribution on a strong statistical footing.

Postoperative Changes of Spinopelvic Sagittal Parameters After Cervical Laminoplasty for Cervical Spondylotic Myelopathy.

A retrospective analysis of prospectively collected data. To investigate postoperative changes of spinopelvic sagittal parameters after laminoplasty for cervical spondylotic myelopathy (CSM) accompanying postoperative cervical kyphotic deformity or cervical regional sagittal imbalance. To the best of our knowledge, no study has been reported concerning postoperative changes of spinopelvic sagittal parameters accompanying postoperative deterioration of cervical sagittal alignment or balance after cervical laminoplasty. Forty-five CSM patients without preoperative cervical kyphosis who underwent laminoplasty were included. None of the 45 patients had a medical history of previous spine surgery, hip joint surgery, or knee joint surgery. The patients were divided into 2 groups (kyphosis and lordosis groups) according to postoperative C2-7 angle, and they were also divided into 2 other groups (imbalance and balance groups) according to postoperative C1-7 sagittal vertical axis. Postoperative changes (Δ) of T1 slope (T1S), thoracic kyphosis, thoracolumbar kyphosis (TLK), lumbar lordosis (LL), Pelvic tilt, and C7 sagittal vertical axis were measured comparing lateral radiographs of the whole spine in the standing position taken at 1 year postoperatively with those before surgery. Both T1S and TLK significantly decreased after cervical laminoplasty in the kyphosis group compared with the lordosis group. On the other hand, both T1S and TLK increased significantly, and LL significantly decreased after surgery in the imbalance group compared with the balance group. At 1 year after laminoplasty for CSM, both T1S and TLK significantly decreased accompanying postoperative cervical kyphotic deformity as a compensatory action for postoperative cervical kyphosis to maintain the global sagittal balance of the spine, whereas both T1S and TLK increased significantly, and LL significantly decreased accompanying postoperative cervical reginal sagittal imbalance which resulted in postoperative forward inclination of the whole spine.

Collective large-scale wind farm multivariate power output control based on hierarchical communication multi-agent proximal policy optimization

Wind power is becoming an increasingly vital source of renewable energy worldwide. However, controlling power generation in wind farms faces significant challenges due to the inherent complexity of these systems. To address this issue and maximize power output, we propose a novel communication-based multi-agent deep reinforcement learning approach for large-scale wind farm control. We introduce a multivariate power model for wind farms to analyze the impact of wake effects on power output. This model considers controllable variables such as axial induction factor, yaw angle, and tilt angle. To coordinate the continuous controls in large-scale wind farms, we propose the hierarchical communication multi-agent proximal policy optimization (HCMAPPO) algorithm. The wind farm is divided into multiple wind turbine aggregators (WTAs), and neighboring WTAs can exchange information through hierarchical communication to optimize power output. Our simulation results demonstrate that the multivariate HCMAPPO approach significantly increases wind farm power output compared to traditional PID control, coordinated model-based predictive control, and the multi-agent deep deterministic policy gradient algorithm. The HCMAPPO algorithm can be trained using a thirteen-turbine wind farm environment and effectively applied to large-scale wind farms. Importantly, as the wind farm scale increases, there is no significant increase in wind turbine blade fatigue damage from wake control. This multivariate HCMAPPO control strategy enables the collective maximization of power output in large-scale wind farms.