Spatial Angle Research Articles

Characteristics of the femoral tunnel of anatomical and isometric single bundle anterior cruciate ligament reconstruction: a modeling analysis based on quadrant method and anatomical landmarks

PurposeTo investigate the anatomical features of the femoral tunnel in anatomical and isometric single-bundle ACL reconstruction.MethodThirty-two 3-dimensional knee models were reconstructed based on CT scan (average age: 26.5 ± 6.7 years, 18 males and 14 females, 17 left and 15 right). Multiple anatomical landmarks were identified. Virtual femoral tunnels were created at the deep and high portion of ACL footprint, close to the lateral intercondylar ridge to achieve best anatomy and isometry, simulating an anteromedial portal reconstruction. Anatomical features of the femoral tunnels were analyzed. The position of the femoral tunnel was quantified by the distance to anatomical landmarks and using quadrant methods. The spatial angles, length and outer opening of the femoral tunnels were also evaluated.ResultsAcceptable tunnels were created in all models. The center of femoral tunnel was slightly higher than the apex of deep cartilage, near the deep one-third point across the shallow-deep dimension of the lateral femoral condyle. Using the quadrant method, the tunnel was located at 28.4% ± 2.2% and 22.2% ± 3.6%, parallel and perpendicular to the Blumensaat line, respectively. The spatial angles of the tunnel were 40°, 33.5° ± 4.1° and 38.2° ± 4.4° on the sagittal, transverse, and coronal planes, respectively. The average tunnel length was 34.8 mm ± 3.8 mm. The outer opening of the tunnels was located at the posterior one-third of the femoral metaphysis.ConclusionThe anatomical and isometric positioning of the femoral tunnel can be achieved through anteromedial portal with satisfied tunnel characteristics. The apex of deep cartilage may be used as an anatomical reference for tunnel positioning. When drilled at appropriate orientation, favorable tunnel length, integrity and position of the outer opening can be obtained.

Parametric Sensitivity Analysis of Mooring Chains of a Floating Offshore Wind Turbine in Shallow Water

Floating offshore wind turbines (FOWTs) are severely restricted in numerous sea areas due to challenges from the strong nonlinear characteristics of mooring chains in shallow water (less than 50 m). Therefore, this paper introduces a design method of mooring chains of a FOWT at a water depth of 44 m and carries out a parametric sensitivity analysis on length, nominal diameter, and clump weights of mooring chains. The results of the study found that compared with the mooring chains in deep water, the mooring chains in shallow water show obvious nonlinear characteristics in mooring tension, the lying section of the mooring chain on the seabed, and the mooring chain spatial angle, which brings great risk to the safe operation of FOWTs. The change in the nominal diameter of the mooring chain has a certain impact on the dynamic characteristics of a FOWT, but it is not as significant as that from the change in the length of the mooring chain. In addition, a mooring chain in shallow water is prone to the slack–taut phenomenon; thus, this paper puts forward an optimization investigation using clump weights at the suspension section of the mooring chain, which improved the performance of the mooring chain significantly.

A comprehensive assessment of meteorological–hydrological indicator changes and their driving forces from a multi-temporal and spatial scale perspective

ABSTRACT Runoff is a pivotal ecohydrological cycle feature. Investigating watershed runoff change and its influencing factors from multi-temporal and spatial angles is crucial for water ecology control. The study analyzes hydrological and meteorological changes using the indicators of hydrological alteration and the range of variation approach (IHA–RVA) and RClimDex to explore their dynamic relationship. Finally, using the soil and water assessment tool to quantify climate and human contributions to runoff temporally and spatially, with validation using Budyko-based elasticity coefficients. Results showed that (1) most of the meteorological indices show an upward trend, a change attributable mainly to strong human activity and global warming. The overall hydrological indicators show a moderate degree of change (50.70%). (2) PRCPTOT (the annual total precipitation) and 30-day minimum demonstrate a negative correlation coefficient of 0.91 in the meteorological–hydrological response. (3) On annual/seasonal scales, human activities such as hydraulic projects and land use/cover changes (LUCC) dominate runoff changes. On a monthly scale, climate change prevails in March and November due to temperature/rainfall fluctuations, while human activities dominate other months. Spatially, climate change and LUCC mainly impact runoff in the southeast. The study offers references to improve water management in the Jialing River Basin, effectively addressing the negative impacts of human activities on runoff.

A New Method for Joint Sparse DOA Estimation.

To tackle the issue of poor accuracy in single-snapshot data processing for Direction of Arrival (DOA) estimation in passive radar systems, this paper introduces a method for judiciously leveraging multi-snapshot data. This approach effectively enhances the accuracy of DOA estimation and spatial angle resolution in passive radar systems. Additionally, in response to the non-convex nature of the mixed norm, we propose a hyperbolic tangent model as a replacement, transforming the problem into a directly solvable convex optimization problem. The rationality of this substitution is thoroughly demonstrated. Lastly, through a comparative analysis with existing discrete grid DOA estimation methods, we illustrate the superiority of the proposed approach, particularly under conditions of medium signal-to-noise ratio, varying numbers of snapshots, and close target angles. This method is less affected by the number of array elements, and is more usable in practices verified in real-world scenarios.

Use of spectral transmittance model to improve the detection accuracy of chromium in soil

As a new quantitative analysis method for heavy-metal elements in soil, the main function of the polarization resolution model is to filter out the disturbance of other elements on the spectral signal of target plasma. In order to quantify the mechanism of improving detection performance, the spectral transmittance of plasma intensity in the polarization-resolved optical path has been derived, and the relationship between the intensity of polarization-resolved laser-induced breakdown spectroscopy (PRLIBS) and the characteristic peak wavelength has been defined. Using the spectral data in the wavelength range of 424.50–429.24 nm as the characteristic signal, a quantitative analysis method for detection of the Cr element in soil has been developed. The improvement of spectral intensity stability at the characteristic peak of Cr I 425.7 was analyzed, and the mechanism of enhancing the detection accuracy was elucidated. Research has shown that, based on the polarization characteristics of Cr element plasma, PRLIBS is not affected by the matrix effects of soil and characterizes the amplitude conversion from the reference concentration of Cr element to the plasma spectral intensity. The spectral transmittance of plasma spectra depends not only on the characteristic peak wavelength and complex refractive index of heavy-metal elements but also on the measurement conditions such as spatial geometric angles and reflectivity of the transmission medium.

Electron cyclotron emission quasi-optical transmission system on the HL-3 tokamak.

A new quasi-optical (QO) Electron Cyclotron Emission (ECE) transmission system has been established on the HL-3 tokamak, which includes a focusing QO mirror combination and a long-distance transmission line. This system was developed to meet the requirements for poloidal spatial resolution and the high signal-to-noise ratio needed for magnetohydrodynamic (MHD) instability studies using ECE on the HL-3. The QO mirror combination was installed inside the vacuum chamber for focusing. Laboratory test results, theoretical calculations, and synthetic ECE simulation results indicate that the Gaussian beam can meet the spatial resolution requirements for the accurate measurement of the MHD instability on the q = 1/2/3 surfaces, corresponding to the poloidal mode numbers m = 3/6/9. This includes good diagnostic poloidal spatial resolution for the important 2/1 and 3/2 modes. At the front end of the transmission line, a high-efficiency mode converter was designed to transition the TE10 mode to the HE11 mode for input into the transmission line, with an insertion loss of less than 1.5 dB. A 30m long-distance corrugated oversized waveguide was constructed, with transmission losses ranging from 6 to 10 dB in the 60-120GHz range. Polarization adjustment results show that the polarization offset and geometric spatial polarization angle change consistently, which can provide a reference for polarization adjustment in other complex structured transmission lines. The newly established ECE QO transmission system will provide strong support for future physics research involving ECE on the HL-3.

Feasibility of augmented reality using dental arch-based registration applied to navigation in mandibular distraction osteogenesis: a phantom experiment

ObjectiveDistraction osteogenesis is a primary treatment for severe mandibular hypoplasia. Achieving the ideal mandible movement direction through precise distraction vector control is still a challenge in this surgery. Therefore, the aim of this study was to apply Optical See-Through (OST) Augmented Reality (AR) technology for intraoperative navigation during mandibular distractor installation and analyze the feasibility to evaluate the effectiveness of AR in a phantom experiment.MethodsPhantom was made of 3D-printed mandibular models based on preoperative CT scans and dental arch scans of real patients. Ten sets of 3D-printed mandible models were included in this study, with each set consisting of two identical mandible models assigned to the AR group and free-hand group. 10 sets of mandibular distraction osteogenesis surgical plans were designed using software, and the same set of plans was shared between the AR and free-hand groups. Surgeons performed bilateral mandibular distraction osteogenesis tasks under the guidance of AR navigation, or the reference of the preoperative surgical plan displayed on the computer screen. The differences in angular errors of distraction vectors and the distance errors of distractor positions under the guidance of the two methods were analyzed and compared.Results40 distractors were implanted in both groups, with 20 cases in each. In intra-group comparisons between the left and right sides, the AR group exhibited a three-dimensional spatial angle error of 1.88 (0.59, 2.48) on the left and 2.71 (1.33, 3.55) on the right, with P = 0.085, indicating no significant bias in guiding surgery on both sides of the mandible. In comparisons between the AR group and the traditional free-hand (FH) group, the average angle error was 1.94 (1.30, 2.93) in the AR group and 5.06 (3.61, 9.22) in the free-hand group, with P < 0.0001, resulting in a 61.6% improvement in accuracy. The average displacement error was 1.53 ± 0.54 mm in the AR group and 3.56 ± 1.89 mm in the free-hand group, with P < 0.0001, indicating a 57% improvement in accuracy.ConclusionAugmented Reality technology for intraoperative navigation in mandibular distraction osteogenesis is accurate and feasible. A large randomized controlled trial with long-term follow-up is needed to confirm these findings.Trial RegistrationThe project has been registered with the Chinese Clinical Trial Registry, with registration number ChiCTR2300068417. Date of Registration: 17 February 2023.

Numerical model and coupled vibration analysis of transmission shaft with spatial angle misalignment

Numerical model and coupled vibration analysis of transmission shaft with spatial angle misalignment

A New Family of Solids: The Infinite Kepler-Poinsot Polyhedra

The so-called Platonic solids have fascinated mathematicians and artists for over 2000 years. It is astonishing that there are only five cases of regular polyhedra, that is, of polyhedra in which regular polygons form the same spatial angles between them in each vertex. In 1619, Kepler added the small and great stellated dodecahedron to this list, but he allowed intersecting faces. Poinsot did so too, in 1809, and discovered the great dodecahedron and great icosahedron. In 20th century, Coxeter and Petrie added three more regular polyhedra, using infinitely repeating elements, based on the truncated tetrahedron, the cube and the truncated octahedron. The principle of intersecting faces, typical for the Kepler-Poinsot solids, can be combined with the Coxeter-Petrie generalization to the infinite case. Thus, a new regular polyhedron was discovered, based on the cubohemioctahedron but without its square faces. Placed side by side and on top of each other, identical regular hexagons meet in each vertex, always with the same spatial angle. There are 8 of them in each vertex, and so it is not a compound of twice two polyhedra with 4 hexagons in each vertex. The dual of this {6, 8} polyhedron of infinite Kepler-Poinsot type is indeed a {8, 6} polyhedron of infinite Kepler-Poinsot type, if two overlapping squares are considered as one 8/4 octagonal star. Kepler-Poinsot solids are difficult to interpret, with their intersecting faces, and this infinite case is even more difficult to grasp. The present paper tries to solve this using open faces so that one can see through the solids.

The influence of talus size and shape on in vivo talocrural hopping kinematics.

Talus morphology (shape and size) plays a pivotal role in talocrural joint function. Despite its importance, the relationship between talus morphology, particularly the talar dome, and dynamic, in vivo talocrural function is poorly understood. Understanding these form-function relationships in a healthy cohort is essential for advancing patient-specific treatments aimed at restoring function. Nine participants (five females) hopped on one leg while biplanar videoradiography and ground reaction forces were simultaneously collected. Three-dimensional bone models were created from computed tomography scans. Helical axes of motion were calculated for the talus relative to the tibia (rotation axes), and a cylinder was fitted through the talar dome (morphological axis). Bland-Altman plots and spatial angles were used to examine the level of agreement between the rotation and morphological axes. A shape model of 36 (15 females) participants was established, and a cylinder fit was morphed through the range of ±3 standard deviations. The rotation and morphological axes largely agree regarding their orientation and location during hopping. The morphological axes were consistently oriented more anteriorly during landing than the rotation axes. Some shape components affect talar dome orientation and curvature independent of size. This suggests that besides bone size, the shape of the talar dome might influence the movement pattern during locomotion. Our findings may further inform talocrural joint arthroplasty design.

Three-Dimensional Bone Alignment from Cone-Beam Computed-Tomography Scans in Weight-Bearing and Clinical Outcomes Following the Modified Grice–Green Surgical Procedure for Adult Acquired Flatfoot

Severe adult-acquired flatfoot deformity is widely addressed surgically via the Grice–Green subtalar arthrodesis. Standard radiographic measurements have been reported, but these are limited to planar views. These complex deformities and the relevant corrections after surgery should be assessed in weight-bearing using 3D analyses now enabled by modern cone-beam CT scans. The present study is aimed at reporting these 3D radiographical foot bone alignments and the clinical results for this surgery. Ten patients were treated with the Grice–Green procedure. This implies inserting an autologous bone graft from the proximal tibial into the extra-articular sinus-tarsi to perform a subtalar arthrodesis. Before and after surgery, the patients were assessed based on the clinical range-of-motion and Foot-Function and Posture Indexes. Three-dimensional models of the tibia, calcaneus, talus, navicular, and 1st metatarsus were reconstructed from cone-beam CT scans in a single-leg up-right posture. Relevant longitudinal axes were defined to calculate ten spatial angles. Post-operatively, a significant realignment was observed for seven angles, including corrections lift-up of the talus (on average by 15°) and subtalar joint (13° in 3D), as well as the Meary’s angle (21°). Only few correlations were found between traditional clinical and novel 3D radiographical measurements, suggesting the former only limitedly represent the corresponding real skeletal status, and the latter thus offer the physician a more comprehensive evaluation. The present original analysis from modern cone-beam CT scans shows precisely the correction of foot and ankle bone alignments achieved using the Grice–Green surgical procedure, finally in 3D and in weight-bearing. For the first time, traditional clinical and score system evaluations are reported together with bone orientation and joint angles in the three anatomical planes.

A Lightweight Hand-Gesture Recognition Network With Feature Fusion Prefiltering and FMCW Radar Spatial Angle Estimation

A Lightweight Hand-Gesture Recognition Network With Feature Fusion Prefiltering and FMCW Radar Spatial Angle Estimation

Hemispherical Retina Emulated by Plasmonic Optoelectronic Memristors with All-Optical Modulation for Neuromorphic Stereo Vision.

Binocular stereo vision relies on imaging disparity between two hemispherical retinas, which is essential to acquire image information in three dimensional environment. Therefore, retinomorphic electronics with structural and functional similarities to biological eyes are always highly desired to develop stereo vision perception system. In this work, a hemispherical optoelectronic memristor array based on Ag-TiO2 nanoclusters/sodium alginate film is developed to realize binocular stereo vision. All-optical modulation induced by plasmonic thermal effect and optical excitation in Ag-TiO2 nanoclusters is exploited to realize in-pixel image sensing and storage. Wide field of view (FOV) and spatial angle detection are experimentally demonstrated owing to the device arrangement and incident-angle-dependent characteristics in hemispherical geometry. Furthermore, depth perception and motion detection based on binocular disparity have been realized by constructing two retinomorphic memristive arrays. The results demonstrated in this work provide a promising strategy to develop all-optically controlled memristor and promote the future development of binocular vision system with in-sensor architecture.

Multi-Target Pairing Method Based on PM-ESPRIT-like DOA Estimation for T/R-R HFSWR

The transmit/receive-receive (T/R-R) synergetic High Frequency Surface Wave Radar (HFSWR) has increasingly attracted attention due to its high localization accuracy, but multi-target pairing needs to be performed before localization in multi-target scenarios. However, existing multi-target parameter matching methods have primarily focused on track association, which falls under the category of information-level fusion techniques, with few methods based on detected points. In this paper, we propose a multi-target pairing method with high computational efficiency based on angle information for T/R-R synergetic HFSWR. To be more specific, a dual-receiving array signal model under long baseline condition is firstly constructed. Then, the amplitude and phase differences of the same target reaching two subarrays are calculated to establish the cross-correlation matrix. Subsequently, in order to extract the rotation factor matrices containing pairing information and improve angle estimation performance, we utilize the conjugate symmetry properties of the uniform linear array (ULA) manifold matrix for generalized virtual aperture extension. Ultimately, azimuths estimation and multi-target pairing are accomplished by combining the propagator method (PM) and the ESPRIT algorithm. The proposed method relies solely on angle information for multi-target pairing and leverages the rotational invariance property of Vandermonde matrices to avoid peak searching or iterations, making it computationally efficient. Furthermore, the proposed method maintains superb performance regardless of whether the spatial angles are widely separated or very close. Simulation results validate the effectiveness of the proposed method.

Human Multi-Activities Classification Using mmWave Radar: Feature Fusion in Time-Domain and PCANet.

This study introduces an innovative approach by incorporating statistical offset features, range profiles, time-frequency analyses, and azimuth-range-time characteristics to effectively identify various human daily activities. Our technique utilizes nine feature vectors consisting of six statistical offset features and three principal component analysis network (PCANet) fusion attributes. These statistical offset features are derived from combined elevation and azimuth data, considering their spatial angle relationships. The fusion attributes are generated through concurrent 1D networks using CNN-BiLSTM. The process begins with the temporal fusion of 3D range-azimuth-time data, followed by PCANet integration. Subsequently, a conventional classification model is employed to categorize a range of actions. Our methodology was tested with 21,000 samples across fourteen categories of human daily activities, demonstrating the effectiveness of our proposed solution. The experimental outcomes highlight the superior robustness of our method, particularly when using the Margenau-Hill Spectrogram for time-frequency analysis. When employing a random forest classifier, our approach outperformed other classifiers in terms of classification efficacy, achieving an average sensitivity, precision, F1, specificity, and accuracy of 98.25%, 98.25%, 98.25%, 99.87%, and 99.75%, respectively.

Prognostic indicators of vector electrocardiography in patients with chronic heart failure with reduced left ventricular ejection fraction

Relevance. Computed vector electrocardiography (VECG) is a method of visualization of the total electrical vector of the heart in 3‑dimensional space based on 12 leads and a known computational procedure. VECG may be an additional method to assess the severity and prognosis of patients with chronic heart failure (CHF).Objective. To determine VECG parameters associated with unfavorable prognosis in patients with CHF with reduced ejection fraction (CHFpEF).Materials and methods. VECGs of 100 patients with CHFpEF were analyzed. All patients underwent baseline clinical examination, echocardiography and natriuretic peptide (NT-proBNP) determination. Patients with both ischemic (55 patients, of whom 10 died) and non-ischemic (45 patients, of whom 6 died) etiologies were included. During follow-up for 24 months, fatal outcomes were recorded. The correlation of ECG and NT-proBNP parameters with patients’ prognosis was evaluated.Results. A total of 16 patients died in the study. According to VECG data the surviving patients had lower spatial QRS-T angle in comparison with the deceased ones (p=0,025). There was a trend towards lower planarity index in the group of deceased patients (p=0.09). ROC-analysis was carried out, according to the results of which with sensitivity 76,5% and specificity 62,7% the cut-off value of 156º of QRS-T spatial angle was obtained, exceeding which the probability of lethal outcome will increase (p=0,002). There was a correlation between lethal outcome in patients with a QRS-T angle value greater than 156º and NT-proBNP level (p=0.017). The threshold value of unfavorable prognosis for NT-proBNP was 927.1 pg/ml.Conclusion. The VECG method is available and promising in the diagnosis and monitoring of patients with CHFpEF. The most informative parameters of ECG for detection of suspicion of CHFpEF are spatial QRS-T angle and planarity index. The results obtained in this study allow us to speak about the prognostic value of the QRS-T angle for patients with CHFpEF.

Compact compressor based on unparallel gratings

The pulse compressor is one of the essential components in a high-power laser system, which is often bulky. Here, we propose a compact compressor based on a Treacy compressor with two unparallel gratings and a mirror. Two gratings provide a negative group delay dispersion, and the mirror has two functions. One is to make the beam enter the compressor twice, and the other is to make the optical path between the grating pair folded to reduce the volume of the compressor. The relation between the group delay dispersion and the incident angle in three-dimensional space is derived. The results show that a small spatial incident angle can produce a large negative dispersion when the perpendicular distance between the gratings is the same. The parameter limits of the designed structure are also discussed, and the volume of compact compressor under the simulated parameters is two-thirds of the conventional compressor when the constraints are satisfied. This work is applicable to the optimal design of grating-based compressors with different parameters.

Effects of the wall temperature on separation flowfield of swept shock wave/boundary layer interactions

Swept shock wave/boundary layer interaction (SWBLI) is a complex flow phenomenon commonly observed in three-dimensional hypersonic inlets. Wall temperatures can influence the scale of the separation of the swept SWBLI. It may lead to inlets unstart, resulting in a significant decrease in mass flow rate. This study delves into the flowfield of swept SWBLI under varying wall temperatures, using both experimental and numerical methods to examine the effects of these temperature changes on the separation scaling and the fluctuating velocity within the SWBLI flowfield. The investigation uncovers that modifications in wall temperature significantly impact the boundary layer's subsonic layer thickness, streamwise momentum distribution, and shear stress, which collectively alter the separation scale. To estimate characteristic surface limiting streamline angles under changed wall temperature conditions, a predictive model is proposed that utilizes the boundary layer shape factor H as a metric. Additionally, it is established that wall temperature variations can influence surface friction coefficients, which can, in turn, affect the pressure rise process during separation and alter the spatial angle of the separation shock. The fluctuating velocity characteristic reveals that the wall temperature affects the separated flow mainly on the incoming boundary layer.

Influence of spatial engagement angles on machining forces and surface roughness in turning of unidirectional CFRP

Carbon fibre-reinforced polymer (CFRP) is being widely used due to its low specific weight and outstanding mechanical properties. However, using identical machining parameters on unidirectional CFRP can lead to different results depending on the fibre orientation.Recently, a process-independent model describing the engagement conditions in oblique cutting of unidirectional CFRP has been developed, introducing the spatial angles θ0 and φ0. Since the engagement conditions of milling and drilling are complex, analogy experiments are conducted in turning with variation of the setting κrand inclination angles λs. In this study, process forces and surface roughness were measured as a function of the complete range of fibre cutting angle θ.

Evaluation of the Degree of Degradation of Brake Pad Friction Surfaces Using Image Processing

The improvement of drilling rig systems to ensure a reduction in unproductive time spent on lowering and lifting operations for replacing drilling tools and restoring the performance of drilling equipment units is an important task. At the same time, considerable attention is paid to the reliable and efficient operation of the braking systems of drilling rig winches. In the process of operation, the polymer pads periodically come into contact with the outer cylindrical surface of the metal pulley during braking, work in extreme conditions and wear out intensively, so they need periodic replacement. Tests were carried out on a modernized stand and in industrial conditions for the brakes of drilling winches. A methodology for evaluating the degradation of the brake pad friction surface during its operation is proposed. The assessment of the degradation degree is carried out based on the image of the brake pad surface using image processing techniques. Geometric transformations of the input image were performed to avoid perspective distortions caused by the concave shape of the brake pads and the spatial angle at which the image is acquired to avoid glares. The crack detection step was implemented based on the scale-space theory, followed by contour detection and skeletonization. The ratios of the area and perimeter of segmented and skeletonized cracks to the total area were chosen as integral characteristics of the degradation degree. With the help of scanning electron microscopy, the character of the destruction of the friction surface and the degradation of the polymer material was investigated. Experimental studies were performed, and the application of the proposed method is illustrated.