Shape Analysis Method Research Articles

A geometric completion and shape analysis method for damaged bilaterally symmetrical artifacts

• A technological framework is proposed for the restoration and analysis of a damaged bilaterally symmetrical artifact. • A hybrid non-rigid deformation approach is proposed to warp the reflection of the intact region to the damaged artifact. • Both geometric morphometrics and anthropometric measurements are used to capture the characteristic features. Archeological artifacts are important forms of tangible cultural heritage, providing evidence of cultural signification, human values, and the development of manufacturing technologies. The reconstruction of damaged bilaterally symmetrical artifacts is frequently undertaken for research and public display. However, traditional restoration technology requires physical intervention, which can cause secondary damage, and raise questions of authenticity. In this study, we proposed a hybrid non-rigid deformation approach to repair damaged bilaterally symmetrical artifacts based on a study of a heavily corroded metal mask of the Liao dynasty from the Palace Museum, China. In addition, since the mask is always placed over the head of the deceased person, it is an interesting question to capture the characteristic features. We employed geometric morphometrics (GM) and anthropometric measurements (AM) to investigate the geometric variations between the mask and human faces. The experimental results demonstrated the effectiveness of the proposed approach in the application of virtual restoration and shape analysis. These methods have wider application to other forms of archeological and anthropological data.

In-situ measurement of interfacial tension: Further insights into effect of interfacial tension on the kinetics of CO2 hydrate formation

Hydrate-based CO2 capture and sequestration has been viewed as one of the most attractive technologies due to its environmental friendliness and relatively moderate temperature and pressure conditions. In current work, the kinetics of CO2 hydrate formation was investigated at pressures of 2.5–3.5 MPa and temperatures of 274.15–279.15 K and the effect of interfacial tension on CO2 hydrate formation rate was discussed. The interfacial tension between CO2 and aqueous solution during the hydrate formation was in-situ measured via an axisymmetric drop shape analysis method. Under the experimental conditions of this study, the interfacial tension decreased significantly with increasing pressure, while it did not vary obviously with temperature. As to SDS aqueous solutions, the interfacial tension at the gas-liquid interface decreased approximately 12% and 42% when the SDS concentration was 100 ppm and 500 ppm, respectively. In addition, CO2 hydrate formation rate ascended by 59% and 102% when the SDS concentration is 100 ppm and 500 ppm, respectively. Furthermore, a good linear relationship was observed between hydrate formation rate and ratio of driving force to interfacial tension (R2 = 0.9211). This work provides a new idea for rapid estimation of hydrate formation rate.

Two-Dimensional Shape Analysis of Complex Geometry Based on Photogrammetric Models of Iconostases

Three-dimensional digitization technologies have been proved as reliable methods for detailed and accurate spatial data collection from existing cultural heritage. In addition, the point segmentation techniques are particularly relevant for contour detection and classification of the unstructured point cloud. This paper describes an approach to obtain 2D CAD-like visualizations of complex geometry from photogrammetric models so that the detected contours of particular object elements can be used for 2D shape analysis. The work process uses the point clouds derived from photogrammetric models to create the plane visualization of the object’s geometry by segmenting points based on the verticality geometric feature. The research presented is on the case studies of iconostases as the specific art and architectural elements of the Christian Orthodox church that can be appreciated only in situ. To determine relations between the characteristics of the particular shapes and the iconostases’ style origins, the mathematical method of shape analysis was applied. This study aims to numerically describe the stylistic characteristics of the shapes of the main parts of the iconostasis concerning the artistic period to which it belongs to. The concept was based on the consideration of global shape descriptors and associated shape measurements which were used to analyze and classify the stylistic characteristics of the iconostases. The methodology was applied to the representative examples of three iconostases from the Baroque and Classicism art movements. The results illustrated that the proposed methods and techniques, with certain improvements, could be helpful for CAD visualization and shape analysis of complex geometry.

Fruit Quality Detection and Gradation

Grading and classification of fruits is based on observations and through experiences. The system exerts image- processing techniques for classification and grading the quality of fruits. Two-dimensional fruit images are classified on shape and color-based analysis methods. However, different fruit images have different or same color and shape values. Hence, using color or shape analysis methods are still not that much effective enough to identify and distinguish fruits images. Therefore, computer vision and image processing techniques have been found increasingly useful in the food industry, especially for applications in quality detection. Research in this area indicates the feasibility of using computer vision systems to improve product quality, the use of computer vision for the inspection of food has increased during recent years. This proposed work presents food quality detection system. The system design considers some feature that includes fruit colors and size, which increases accuracy for detection of roots pixels. Histogram of oriented gradients is used for background removal, for color classification, support vector machine is used.

Landmark-free morphometric analysis of knee osteoarthritis using joint statistical models of bone shape and articular space variability.

Purpose: Osteoarthritis (OA) is a common degenerative disease involving a variety of structural changes in the affected joint. In addition to narrowing of the articular space, recent studies involving statistical shape analysis methods have suggested that specific bone shapes might be associated with the disease. We aim to investigate the feasibility of using the recently introduced framework of functional shapes (Fshape) to extract morphological features of OA that combine shape variability of articular surfaces of the tibia (or femur) together with the changes of the joint space. Approach: Our study uses a dataset of three-dimensional cone-beam CT volumes of 17 knees without OA and 17 knees with OA. Each knee is then represented as an object (Fshape) consisting of a triangulated tibial (or femoral) articular surface and a map of joint space widths (JSWs) measured at the points of this surface (joint space map, JSM). We introduce a generative atlas model to estimate a template (mean) Fshape of the sample population together with template-centered variables that model the transformations from the template to each subject. This approach has two potential advantages compared with other statistical shape modeling methods that have been investigated in knee OA: (i)Fshapes simultaneously consider the variability in bone shape and JSW, and (ii)Fshape atlas estimation is based on a diffeomorphic transformation model of surfaces that does not require a priori landmark correspondences between the subjects. The estimated atlas-to-subject Fshape transformations were used as input to principal component analysis dimensionality reduction combined with a linear support vector machine (SVM) classifier to identify the morphological features of OA. Results: Using tibial articular surface as the shape component of the Fshape, we found leave-one-out cross validation scores of for the classification based on the bone surface transformations alone, for the classification based on the residual JSM, and for the classification using both Fshape components. Similar results were obtained using femoral articular surfaces. The discriminant directions identified in the statistical analysis were associated with medial narrowing of the joint space, steeper intercondylar eminence, and relative deepening of the medial tibial plateau. Conclusions: The proposed approach provides an integrated framework for combined statistical analysis of shape and JSPs. It can successfully extract features correlated to OA that appear consistent with previous studies in the field. Although future large-scale study is necessary to confirm the significance of these findings, our results suggest that the functional shape methodology is a promising new tool for morphological analysis of OA and orthopedics data in general.

ESTIMATING THE SURVIVAL OF AQUA FAUNA BY IMAGE ANALYSIS TECHNIQUES FROM THE VIDEO SEQUENCES OF POND AQUACULTURE

Survival status of aqua fauna is estimated by studying the dynamic behaviour (motion) in underwater environment. Survival status of aqua fauna particularly, shrimp is estimated to prevent huge economic losses to the aqua farmers. A novel approach has been proposed in this research work to address this issue through segmentation, extraction of features, motion analysis and classification of aqua fauna from the pond aquaculture video sequences. First, the content-based video is translated into frames, and the image content is segmented using the Background Subtraction algorithm. Then, shrimp motion analysis is done with the assistance of the optical Flow algorithm. At the same time, shrimp body feature is extracted by Edge detection method for Shape analysis. Finally, the Decision Tree classifier is constructed to estimate the status of shrimp is alive or dead. Real-time video sequences of shrimp in pond aquaculture have illustrated the effectiveness of our process. The projected method shows that the results are more accurate to estimate the shrimp survival status as well as providing GMP (Good Manufacturing Practices) in shrimp cultivation to alert the aqua farmers in advance to avoid economic loss

Next-generation osteometric sorting: Using 3D shape, elliptical Fourier analysis, and Hausdorff distance to optimize osteological pair-matching.

Determining which bilateral bones belong to the same person based on shape and size similarity is called pair-matching and it is instrumental for sorting commingled skeletons. To date, pair-matching has popularly been accomplished by visual inspection and/or linear caliper measurements; however, attention is turning increasingly to computational analysis. In this paper, we investigate a fast three-dimensional (3D) computerized shape-analysis method for whole-bone pair-matching using a test sample of 14 individuals (23 femora, 26 humeri, and 26 tibiae). Specifically, the method aims to find bilateral pairs using, as the shape signature criterion, a single 3D outline that snakes around each bone's perimeter as described by a 3D elliptical Fourier analysis function. This permits substantial 3D-point-cloud data reduction, that is, to 0.02% of the starting c.500,000 point cloud or just 100 points, while preserving key 3D shape information. The mean Hausdorff distance (Hd) was applied to measure the distance between each mirrored right-side outline to every left-side outline in pairwise fashion (132, 168 and 169 comparisons, respectively). Both thresholds and lowest Hd were investigated as pair-match criteria, with the lowest Hd producing the best performance results for searches jointly utilizing right-left and left-right directions for comparison: true positive rates of 1.00 (10/10), 1.00 (12/12), and 0.92 (11/12) for the femora, humeri, and tibiae, respectively. The computational time to calculate 469 pairwise 3D comparisons on a single stock-standard Intel® Core™ i7-4650U CPU @ 1.70GHz was 5s. This short data processing time makes the method viable for real-world application.

Retrosternal Deformations after Coronary Artery Bypass Surgery Using Statistical Shape Analysis.

IntroductionIn this study, we aimed to evaluate the anatomical deformations of the major vascular structures in the retrosternal area caused by adhesions following coronary artery bypass grafting (CABG).MethodsThis single-center, retrospective study included a total of 40 patients with a previous CABG who were admitted to our emergency unit for any reason and underwent a contrast-enhanced chest computed tomography (patient group) and 40 patients without previous cardiac surgery (control group) between January 2018 and November 2019. The retrosternal area was compared between the groups using the statistical shape analysis method. The distance between the sternum and the ascending aorta and pulmonary artery was measured and anatomical deformations of the retrosternal area were examined.ResultsThere was a statistically significant difference in the anatomical structures of the retrosternal area between the patient and control groups (P<0.001). The distance from the midsternal line to the highest point of the pulmonary artery was statistically significantly shorter in the patient group, compared to the control group (P=0.013). The distance from the sternum to the ascending aorta was also shorter in the patient group, although it did not reach statistical significance (P>0.05).ConclusionsOur study results showed narrowing of the retrosternal area following CABG and a shorter distance from the sternum to the pulmonary artery than the ascending aorta. Based on these findings, surgeons should be cautious about possible injuries in patients requiring cardiac surgery with repeated median sternotomy.

Statistical shape analysis pre-processing of temperature modulated metal oxide gas sensor response for machine learning improved selectivity of gases detection in real atmospheric conditions

Development of new signal processing approaches is essential for improvement of the reliability of metal oxide gas sensor performance in real atmospheric conditions. Advantages statistical shape analysis (SSA) method are presented in comparison to previously reported signal pre-processing techniques – principal component analysis (PCA), discrete wavelet transform (DWT), polynomial curve fitting (PCF) – used in combination with machine learning (ML) algorithm for improvement of detection selectivity. An enhanced identification of chemically related gases (methane and propane) at a concentration range of 40−200 ppm under variable real atmospheric conditions has been demonstrated using working temperature modulated metal oxide gas sensors. Laboratory samples of sensors based on nanocrystalline SnO2 modified with Au and Pd were used. The proposed data pre-processing algorithm is less sensitive to sensor response and baseline drift and fluctuations compared to other methods during two months of continuous operation and work with periods of inactivity. The collected dataset and signal processing code are made public. The advantages of SSA signal pre-processing method are also demonstrated with the use of independent publicly available dataset for the task of CO selective quantitative detection in the air with variable humidity in the 2.2−20 ppm concentrations range.

A new certified reference material for size and shape analysis of nanorods using electron microscopy

A new certified reference material (CRM) for size and shape analysis of elongated nanoparticles has been developed by the European Commission’s Joint Research Centre. The CRM consists of titanium dioxide nanorods dispersed in 1-butanol, was coded ERM-FD103 and has been certified for different electron microscopy–based operationally defined measurands such as the modal and median values of the particle number-weighted distributions of the minimum and maximum Feret diameter, the maximum inscribed circle diameter, the area-equivalent circular diameter and the aspect ratio. The nanorods have nominal dimensions of 15 nm in width and 55 nm in length. Homogeneity and stability measurements were performed using transmission electron microscopy. The relative standard uncertainty for homogeneity ranged from 0.3 to 1.7%. No significant instability was detected for a shelf life of 18 months and a storage temperature of 18 °C. The certified values have been determined from the results of an interlaboratory comparison in which qualified expert laboratories participated with scanning and transmission electron microscopy. The certified values are traceable to the unit of length in the International System of Units, the metre, and the relative expanded uncertainties (confidence level of approximately 95%) range from 4 to 6%. These properties allow the CRM to be used for quality assurance and calibration of electron microscopy methods for nanoparticle size and shape analysis in ranges relevant for the implementation of EU legislation related to nanomaterials. The presented study discusses the purpose and results of the different steps that were followed to turn an industrially relevant raw titanium dioxide nanorod material into a fit-for-purpose CRM.Graphical abstract

Shape difference of mud clasts depending on depositional facies: application of newly modified elliptic Fourier analysis to hybrid event beds

ABSTRACT Hybrid event beds are the deposits from sediment gravity flows that change their rheological behavior through their passage, entraining muddy sediments and damping turbulence. Muddy facies of hybrid event beds are often associated with abundant mud clasts which show a wide variety of size and shape. The variation of clast occurrence in hybrid event beds is expected to preserve the information of entrainment and transport processes of muddy sediments in submarine density currents. However, previous analyses of hybrid event beds have focused on describing the overall clast occurrence rather than the statistical size and shape analyses because traditional shape parameters are incapable of characterizing the complex shape of mud clasts. Here, a new quantitative grain-shape analysis of mud clasts is conducted and allows visualization of the spatial variation of clast size and shape, which suggests the wide variety of origin and transport systems of entrained mud clasts. This new method revises the traditional elliptic Fourier analysis, substituting Fourier power spectra (FPS) for traditional elliptic Fourier descriptors to overcome the mirror-wise shape problem. Further, principal-component analysis is shown to capture significant shape attributes more effectively than traditional shape parameters. The proposed method is applied to mud clasts in sediment-gravity-flow deposits in the lower Pleistocene Otadai Formation, central Japan. Results imply that there are distinctive shape and size differences of mud clasts that are strongly associated with depositional facies rather than the distance from the source. The clasts have a higher angularity than other facies in the debrite intervals in hybrid event beds. It is also shown that clasts in sandy, structureless facies have different characteristics in shapes based on elongation and convexity compared to laminated facies. Comparison between different shape-analysis methods demonstrates that none of the traditional methods are able to visualize these trends as effectively as the method presented herein. These results highlight the importance of the quantitative shape analysis of sediment grains and the effectiveness of FPS-based elliptic Fourier analysis.

Analysis of the EMCCD point-source response using x-rays

Electron Multiplying Charge Coupled Devices, EMCCD are used as x-ray detectors. The NSLS-II Soft Inelastic x-ray Scattering (SIX) beam line has two EMCCDs for x-ray detection in the spectrometer arm. The spectrometer with high resolving power disperses x-rays vertically. The x-ray vertical position on the sensor plane is related to its energy. This allows for very accurate x-ray energy measurements through x-ray coordinates. X-rays interact with silicon and create a number of electron–hole pairs proportional to the x-ray energy. Electrons drift and diffuse toward pixel gates and are collected there. The diffused electrons form a charge cloud distributed over several neighboring pixels. This charge sharing enables coordinate measurements with accuracy better than the pixel pitch. The charge distribution shape has to be taken into account to achieve ultimate accuracy in coordinate measurements. In this paper, we present a method of the charge distribution shape analysis and demonstrate its applications.The drift and diffusion of electrons from the point of generation to pixel gates results in the bell-shaped electron cloud usually approximated by Gaussian shape. The number of electrons collected under a pixel is proportional to the shape function integral. These electron packets get transferred to the sense node of the output amplifier. The transfer process could introduce distortions to the original charge distribution. For example, during transfers, electrons in the packet could be exposed to traps if they are present in the sensor. The trapping and later the release processes distort the apparent shape of the charge distribution. Therefore, deviations of the charge distribution shape from the originally symmetrical form can indicate the presence of trap centers in the sensor and can be used for sensor diagnostics.

A new approach to particle shape quantification using the curvature plot

Particle shape measurement is an important analysis for a number of research and industrial disciplines. Most of the presently available 2-Dimensional shape analysis methods commonly suffer from at least two shortcomings: (1) particles, which are visually distinct, are not easily distinguished and (2) the parameter value is difficult to relate to physical attributes. This contribution seeks to address these issues by introducing the Curvature (κ) plot which can be used to identify particle corners and measure their sharpness. Using the κ plot, four shape parameters are proposed: number of corners, cumulative angularity, sharpest corner and straight fraction. This methodology is applied to synthetic geometrical shapes and 4000 natural sand particle data. The results demonstrate that the four new shape parameters can be collectively used to quantitatively describe particle shape which correlates closely with visual perceptions of particle boundary.

Interfacial interactions between oleic acid and betaine molecules at decane-water interface: A study of dilational rheology

The interfacial interactions between organic acid and betaine molecules play an important role in reducing interfacial tension (IFT). To deeply detect the arrangements of organic acid and betaine molecules at the interface, the dilational rheological properties of mixed adsorption films formed by oleic acid and octadecyl carboxyl betaine (18PC) or octadecyl sulfobetaine (18PS) were investigated using drop shape analysis method at the decane-water interface. The influences of aging time, oscillation frequency and surfactants concentration were detected. The experimental results show that the properties of 18PC and 18PS adsorption film are controlled by both the fast diffusion-exchange process between the bulk and the interface and the slow re-arrangement process in the interface. 18PC film is tighter than that of 18PS because the size of carboxyl is small than sulfonyl. Oleic acid and betaine surfactants can form mixed adsorption films with less strength caused by the rapid transfer of oleic acid between the bulk and the interface, but more elastic due to the enhancement of the intermolecular interaction. In this case, the oleic acid molecules are easier to insert into the spaces between 18PS molecules on the interface, which results in a more tight mixed film than oleic acid/18PC film.

Shape analysis of H ii regions – II. Synthetic observations

ABSTRACT The statistical shape analysis method developed for probing the link between physical parameters and morphologies of Galactic H ii regions is applied here to a set of synthetic observations (SOs) of a numerically modelled H ii region. The systematic extraction of H ii region shape, presented in the first paper of this series, allows for a quantifiable confirmation of the accuracy of the numerical simulation, with respect to the real observational counterparts of the resulting SOs. A further aim of this investigation is to determine whether such SOs can be used for direct interpretation of the observational data, in a future supervised classification scheme based upon H ii region shape. The numerical H ii region data were the result of photoionization and radiation pressure feedback of a 34 M⊙ star, in a 1000 M⊙ cloud. The SOs analysed herein comprised four evolutionary snapshots (0.1, 0.2, 0.4, and 0.6 Myr), and multiple viewing projection angles. The shape analysis results provided conclusive evidence of the efficacy of the numerical simulations. When comparing the shapes of the synthetic regions to their observational counterparts, the SOs were grouped in amongst the Galactic H ii regions by the hierarchical clustering procedure. There was also an association between the evolutionary distribution of regions and the respective groups. This suggested that the shape analysis method could be further developed for morphological classification of H ii regions by using a synthetic data training set, with differing initial conditions of well-defined parameters.

Stick-slip behavior of sessile drop on the surfaces with irregular roughnesses

In this work, sessile drop and low-bond axisymmetric drop shape analysis methods were coupled to provide some new aspects on stick-slip behavior as well as stick time of a drop on calcite surfaces. Slightly hydrophobic calcite surfaces typified with three irregular roughnesses were used to create irregular surfaces to mimic defects for the water-calcite-air systems. Polishing papers of 200, 600, and 1200 grit and a polishing machine were used to prepare surfaces. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared, and atomic force microscopy techniques were employed to evaluate the chemical and physical properties of surfaces. A model was developed to predict stick time based on the Laplace equation to take into account the effect of gravity which is neglected in the spherical cap model. An irregular stick–slip behavior of the three-phase contact line was observed for different roughness levels. Increasing roughness level from nono-metric to micrometric scale induced variation of 77.4°, 9.0e−03 mN/m, 1.23 mN/m to 67°, 293.0e−03 mN/m, 7.20 mN/m for the datum contact angle, scaled energy barrier, and the unbalanced Young force per unit length, respectively. Comparison of the models predictions and the obtained experimental data of stick times in this work, showed that the developed model is more accurate than the spherical cap model. This work could provide new insights into the wetting phenomenon of surfaces with irregular roughnesses.

A Comparison of Spherical Harmonic and Sliding Semilandmark Analyses as Methods for Three‐Dimensional Shape Evaluation

The ability to quantify morphological variation is integral to biological research. The use of sliding semilandmarks in geometric morphometric (GM) analyses allows for the evaluation of whole bone morphology in three dimensions. A sliding semilandmark analysis, however, is difficult to complete when structures lack obvious homologous features for landmark placement. Spherical harmonics (SPHARM) offers an alternative method for shape analysis in such cases. Here we evaluate the SPHARM method by comparing results to those from a sliding semilandmark analysis of the calcaneus in African apes and modern humans.Modern human (n=20), chimpanzee (n=20), and gorilla (n=20) calcanei were surface scanned. For the GM analysis, 1007 sliding semilandmarks were evenly distributed across the external surface of each calcaneus. Semilandmarks were slid to minimize the bending energy of the thin plate spline interpolation function relative to an updated Procrustes average. Final landmark configurations were then aligned using Generalized Procrustes Analysis. For the SPHARM analysis, surface models were mapped onto the surface of a sphere (parameterization), and then decomposed into a weighted sum of spherical harmonic functions. Because the spherical harmonics provide a standardized basis for quantifying shape, coefficients of the harmonic functions can be used as shape descriptors. Calcaneal shape variation was summarized using a principal components (PC) analysis of the Procrustes coordinates and SPHARM coefficients. Analyses were compared through calculation of the root mean square (RMS) and maximum distance between surface models of the average specimen from each species, as well as surface models of PC warps created two standard deviations from the average along PCs 1–3.Both sliding semilandmark and SPHARM analyses separate species along the first two PCs. For both analyses, African apes and modern humans separate along PC1. Average RMS between species averages was 0.25 mm. Maximum surface distances between average surface models from the two analyses were all less than 0.23 mm. Average RMS between all respective PC warps was 0.82 mm. Maximum surface distances between PC warps were all less than 1 mm. Although there were minor differences between PC plots produced from the two analyses, the same general morphological distinctions between species were identified. The primary differences between SPHARM and sliding semilandmark‐based surface models of PC warps and species averages occur around sharp edges, which are less defined using the SPHARM analysis, although these differences are small. Overall, SPHARM provides the same shape representation as a sliding semilandmark analysis, making it a comparable method for the evaluation of shape in three dimensions.Support or Funding InformationThis project was supported by NSF grant # BCS ‐ 1824630.

Effect of Added Tetraalkylammonium Counterions on the Dilational Rheological Behaviors of N-Cocoyl Glycinate.

Ion specific effect, which is also known as Hofmeister effect, has been reported in numerous systems including ionic surfactant aggregates. Acyl amino acid surfactants have attracted growing attentions in the field of novel surfactants research due to their environmentally benign characteristics. The objective of this study was to investigate the effect of different salts containing NH4+ and tetraalkylammonium (TAA+), where alkyl = methyl (TMA+), ethyl (TEA+), and propyl (TPA+), cations on the dilational rheological properties of interfacial film are stabilized by potassium N-cocoyl glycinate (KCGl). The interfacial behaviors were studied using oscillating drop shape analysis method. The interfacial tensions (IFTs) and dilational rheological parameters results illustrate that KCGl in the presence of salts has better interfacial activity and stronger intermolecular interaction, indicating that added cations contribute to denser molecular packing at oil-water interface. Ion specific effects were observed in the system. Among the cations, KCGl shows highest dilational modulus in the presence of NH4+. The overall interaction between cations and headgroups of KCGl decreases in the sequence NH4+ >TMA+ >TEA+ ≈TPA+, which follows Hofmeister series. The increasing hydrophobicity of TAA+ prevents the interaction between cations and KCGl's headgroup, and therefore prevent amphiphiles from packing closely at interface. The results present a theoretical origin for useful application of KCGl in cosmetics, petroleum and daily chemical industries.

Temperature dependence of spin pumping and inverse spin Hall effect in permalloy/Pt bilayers

The temperature dependence of the spin pumping process in Fe80Ni20 (Py)/Pt bilayers is analyzed for different Pt capping layer thickness. Samples have been grown by means of dc magnetron sputtering, at room temperature, on top of Si substrates. In order to get an optimized interface between the Py and the Pt layers, the Pt capping layers were deposited In situ. The values of the damping constant, α, obtained for the Py alone samples, around 0.007 at RT, make evident the good quality of the samples. The increase of α due to spin pumping into the Pt layer is clearly appreciated; α values in Py/Pt bilayers are twice the value in Py alone. Spin pumping is confirmed by direct measurements of the inverse spin Hall effect (ISHE) voltage signal (VISHE) measured across the samples. To separate ISHE and spin rectification contributions to VISHE the line shape analysis method has been used and the conditions for its applicability thoroughly discussed. VISHE increases almost linearly on lowering temperature for all the frequencies investigated and smoothly increases as frequency decreases showing roughly a linear dependence with the inverse of the frequency. The Pt layer thickness dependence of α and VISHE suggest a low interfacial spin mixing conductance and high spin memory loss.

Chord Bunch Walks for Recognizing Naturally Self-Overlapped and Compound Leaves.

Effectively describing and recognizing leaf shapes under arbitrary variations, particularly from a large database, remains an unsolved problem. In this research, we attempted a new strategy of describing leaf shapes by walking and measuring along a bunch of chords that pass through the shape. A novel chord bunch walks (CBW) descriptor is developed through the chord walking behavior that effectively integrates the shape image function over the walked chord to reflect both the contour features and the inner properties of the shape. For each contour point, the chord bunch groups multiple pairs of chords to build a hierarchical framework for a coarse-to-fine description that can effectively characterize not only the subtle differences among leaf margin patterns but also the interior part of the shape contour formed inside a self-overlapped or compound leaf. Instead of using optimal correspondence based matching, a Log-Min distance that encourages one-to-one correspondences is proposed for efficient and effective CBW matching. The proposed CBW shape analysis method is invariant to rotation, scaling, translation, and mirror transforms. Five experiments, including image retrieval of compound leaves, image retrieval of naturally self-overlapped leaves, and retrieval of mixed leaves on three large scale datasets, are conducted. The proposed method achieved large accuracy increases with low computational costs over the state-of-the-art benchmarks, which indicates the research potential along this direction.