Geometrical Symmetry Research Articles

Ophthalmoergonomic Test “Glazomer”: Clinical Standardization, Application Prospects

Purpose. Clinical standardization and assessment of the prospects for using the ophthalmoergonomic test “Glazomer” (TG) in a comprehensive examination of the functional state of the visual analyzer of patients engaged in visually intense work (VST).Methods. The test methodology involves sequentially presenting geometric figures (square, circle, rhombus, etc.) on a computer screen that have signs of geometric symmetry and a circumscribed circle diameter of 4–7 cm (angular size of 3.8–6.70 from a distance of 60 cm). The patient’s task was to position the cursor in the center of the figure and fix this position using the “mouse”. There were 12 figures, the presentation time was unlimited or 3, 5 and 10 seconds. The study involved 34 male volunteers aged 28–36 years (mean age 32.4 ± 1.1 years) with no visual organ pathology and cognitive impairment. Based on the study results, two parameters were calculated to assess the accuracy of the eye: the average value of the positioning error — the deviation from the test object center (VOC, mm) and the standard deviation of the error — the spread value (SV, mm).Results. The data obtained indicate that with a decrease in the test presentation time, there was a deterioration in the accuracy of the eye. At the same time, the standardized indicators for the TG are: VOC — no more than 2.54 mm; SV — no more than 0.52 mm. It is important to emphasize that the accuracy of the eye under time “deficit” (3 sec) is a sufficiently informative indicator that determines, along with traditional approaches, the clinical effectiveness of the proposed technologies for treating VST patients with cataracts and accommodative asthenopia after refractive (LASIK) surgery. In particular, it has been established that the presence of anisometropia in a patient after surgical intervention is accompanied by a significantly more pronounced (compared to patients without anisometropia) deterioration in visual performance under conditions of time “deficit”.Conclusion. Practical implementation of TG in a comprehensive examination of the functional state of the visual analyzer of patients with VST with cataracts or accommodative disorders will ensure an increase in the level of diagnostics from the standpoint of the “medical and social” health model.

Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surface-Assisted Non-Orthogonal Multiple Access Wireless Education Network Under Multiple Interference Devices

Reconfigurable Intelligent Surfaces (RISs) and Non-Orthogonal Multiple Access (NOMA) have emerged as key technologies for next-generation (6G) wireless networks, attracting significant attention from researchers. As an advanced extension of RISs, Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surfaces (STAR-RISs) offer superior geometric and functional symmetry due to their capability to simultaneously reflect and transmit signals, thereby achieving full 360° spatial coverage. This symmetry not only ensures balanced energy distribution between the Transmission (T) and Reflection (R) regions but also facilitates interference cancellation through phase alignment. Furthermore, in NOMA networks, the symmetric allocation of power coefficients and the tunable transmission and reflection coefficients of STAR-RIS elements aligns with the principle of resource fairness in multi-user systems, which is crucial for maintaining fairness under asymmetric channel conditions. In this study, key factors, such as interference sources and distance effects, are considered in order to conduct a detailed analysis of the performance of STAR-RIS-assisted NOMA wireless education networks under multiple interference devices. Specifically, a comprehensive analysis of the Signal-to-Interference-plus-Noise Ratio (SINR) for both near-end and far-end devices is conducted, considering various scenarios, such as whether or not the direct communication link exists between the base station and the near-end device, and whether or not the near-end device is affected by interference. Based on these analyses, closed-form approximate expressions for the outage probabilities of the near-end and far-end devices, as well as the closed-form approximation for the system’s Spectral Efficiency (SE), are derived. Notably, the Gamma distribution is used to approximate the square of the composite channel amplitude between the base station and the near-end device, effectively reducing computational complexity. Finally, simulation results validate the accuracy of our analytical results. Both numerical and simulation results show that adjusting the base station’s power allocation, and the transmission and reflection coefficients of the STAR-RIS, can effectively mitigate the impact of interference devices on the near-end device and enhance the communication performance of receiving devices. Additionally, increasing the number of STAR-RIS elements can effectively improve the overall performance of the near-end device, far-end device, and the entire system.

Nonlinear geometric phase in optics: Fundamentals and applications

Pancharatnam–Berry phase, the manifestation of geometric phase in optics, which originates from the adiabatic evolution of light in the anisotropic medium, has been widely explored in the past decades. With the rapid development of nonlinear metamaterials and metasurfaces, the concept of geometric phase has been extended to the regime of nonlinear optics and attracts growing interest due to its capability of manipulating the nonlinear optical fields. On the one hand, nonlinear geometric phase offers a platform to investigate the fundamental principles in light–matter interactions during the nonlinear optical processes. On the other hand, it can be applied to design nonlinear optical elements with versatile functionality, such as wavefront engineering, optical imaging, and optical holography. To give a comprehensive review of nonlinear geometric phase, here, we overview the fundamental mechanisms, including the symmetry selection rules, the origin of the geometric phase in harmonic generations, and the characteristics of nonlinear geometric phase. We summarize the related applications based on the concepts of nonlinear geometric phase and symmetry selection rules, mainly focusing on the recent progresses from nonlinear optical sources to nonlinear optical field manipulation and beyond. In addition to reviewing the achievements in a wide variety of applications based on the nonlinear geometric phase, we also give prospects on their future development. With distinctive features, nonlinear geometric phase may find its importance in not only scientific research but also industrial applications.

Efficient equivariant model for machine learning interatomic potentials

In modern computational materials, machine learning has shown the capability to predict interatomic potentials, thereby supporting and accelerating conventional molecular dynamics (MD) simulations. However, existing models typically sacrifice either accuracy or efficiency. Moreover, efficient models are highly demanded for offering simulating systems on a considerably larger scale at reduced computational costs. Here, we introduce an efficient equivariant graph neural network (E2GNN) that can enable accurate and efficient interatomic potential and force predictions for molecules and crystals. Rather than relying on higher-order representations, E2GNN employs a scalar-vector dual representation to encode equivariant features. By learning geometric symmetry information, our model remains efficient while ensuring prediction accuracy and robustness through the equivariance. Our results show that E2GNN consistently outperforms the prediction performance of the representative baselines and achieves significant efficiency across diverse datasets, which include catalysts, molecules, and organic isomers. Furthermore, we conduct MD simulations using the E2GNN force field across solid, liquid, and gas systems. It is found that E2GNN can achieve the accuracy of ab initio MD across all examined systems.

Planar chlorination engineering induced symmetry-broken single-atom site catalyst for enhanced CO2 electroreduction

Breaking the geometric symmetry of traditional metal-N4 sites and further boosting catalytic activity are significant but challenging. Herein, planar chlorination engineering is proposed for successfully converting the traditional Zn-N4 site with low activity and selectivity for CO2 reduction reaction (CO2RR) into highly active Zn-N3 site with broken symmetry. The optimal catalyst Zn-SA/CNCl-1000 displays a highest faradaic efficiency for CO (FECO) around 97 ± 3% and good stability during 50 h test at high current density of 200 mA/cm2 in zero-gap membrane electrode assembly (MEA) electrolyzer, with promising application in industrial catalysis. At -0.93 V vs. RHE, the partial current density of CO (JCO) and the turnover frequency (TOF) value catalyzed by Zn-SA/CNCl-1000 are 271.7 ± 1.4 mA/cm2 and 29325 ± 151 h-1, as high as 29 times and 83 times those of Zn-SA/CN-1000 without planar chlorination engineering. The in-situ extended X-ray absorption fine structure (EXAFS) measurements and density functional theory (DFT) calculation reveal the adjacent C-Cl bond induces the self-reconstruction of Zn-N4 site into the highly active Zn-N3 sites with broken symmetry, strengthening the adsorption of *COOH intermediate, and thus remarkably improving CO2RR activity.

The Last Piece of the Puzzle: Access to 7‐Connected Zirconium Metal‐Organic Frameworks for Hexane Separation

Zirconium metal‐organic frameworks (Zr‐MOFs) exhibit a wide range of Zr6 cluster connectivities, from 3‐connected to 12‐connected, enabling diverse structural designs. However, odd‐numbered connectivities, especially the 7‐connected Zr‐MOFs, are exceptionally rare due to geometric symmetry challenges. To address this, we developed a geometric pre‐assembly strategy to achieve targeted cluster connectivity. Using this approach, we synthesized NU‐5001 {[Zr6O4(OH)4(H4‐L)2]}, a Zr‐MOF featuring 7‐connected Zr6 clusters, derived from the precursor 6‐connected Zr‐MOF, NU‐5000 {[Zr6O4(OH)4(H3‐L)2]}. NU‐5000, constructed with a tritopic chiral linker H3‐L {(R)‐4,4',4''‐[6'‐chloro‐2,2'‐diethoxy‐(1,1'‐binaphthalene)‐4,4',6‐triyl]tribenzoic acid}, forms a (3,6)‐connected ant topology. Introducing a tetratopic chiral linker, 1,1'‐bi‐2‐naphthol tetracarboxylic acid H4‐L {(R)‐4,4',4'',4'''‐[2,2'‐diethoxy‐(1,1'‐binaphthalene)‐4,4',6,6'‐tetrayl]tetrabenzoic acid}, enabled an additional connection, resulting in NU‐5001 with a (3,4,7)‐connected topology. The H4‐L linker acts as either fully 4‐connected or 3‐connected with one arm uncoordinated. Additionally, NU‐5001M {[Zr6O4(OH)4(H4‐L) (H3‐L)]}, an isostructural variant, was synthesized using a mix of H3‐L and H4‐L linkers. NU‐5001’s unique pore structure and slight flexibility enable distinct adsorption behaviors for hexane isomers, highlighting its potential for kinetic separations. This work completes the Zr6 cluster connectivity landscape and demonstrates the feasibility of tuning Zr‐MOF connectivities through rational linker design, paving the way for rare, low‐symmetry frameworks with tailored properties.

The Last Piece of the Puzzle: Access to 7-Connected Zirconium Metal-Organic Frameworks for Hexane Separation.

Zirconium metal-organic frameworks (Zr-MOFs) exhibit a wide range of Zr6 cluster connectivities, from 3-connected to 12-connected, enabling diverse structural designs. However, odd-numbered connectivities, especially the 7-connected Zr-MOFs, are exceptionally rare due to geometric symmetry challenges. To address this, we developed a geometric pre-assembly strategy to achieve targeted cluster connectivity. Using this approach, we synthesized NU-5001 {[Zr6O4(OH)4(H4-L)2]}, a Zr-MOF featuring 7-connected Zr6 clusters, derived from the precursor 6-connected Zr-MOF, NU-5000 {[Zr6O4(OH)4(H3-L)2]}. NU-5000, constructed with a tritopic chiral linker H3-L {(R)-4,4',4''-[6'-chloro-2,2'-diethoxy-(1,1'-binaphthalene)-4,4',6-triyl]tribenzoic acid}, forms a (3,6)-connected ant topology. Introducing a tetratopic chiral linker, 1,1'-bi-2-naphthol tetracarboxylic acid H4-L {(R)-4,4',4'',4'''-[2,2'-diethoxy-(1,1'-binaphthalene)-4,4',6,6'-tetrayl]tetrabenzoic acid}, enabled an additional connection, resulting in NU-5001 with a (3,4,7)-connected topology. The H4-L linker acts as either fully 4-connected or 3-connected with one arm uncoordinated. Additionally, NU-5001M {[Zr6O4(OH)4(H4-L) (H3-L)]}, an isostructural variant, was synthesized using a mix of H3-L and H4-L linkers. NU-5001's unique pore structure and slight flexibility enable distinct adsorption behaviors for hexane isomers, highlighting its potential for kinetic separations. This work completes the Zr6 cluster connectivity landscape and demonstrates the feasibility of tuning Zr-MOF connectivities through rational linker design, paving the way for rare, low-symmetry frameworks with tailored properties.

An efficient and high-quality scheme for cone-beam CT reconstruction from sparse-view data.

Computed tomography (CT) is capable of generating detailed cross-sectional images of the scanned objects non-destructively. So far, CT has become an increasingly vital tool for 3D modelling of cultural relics. Compressed sensing (CS)-based CT reconstruction algorithms, such as the algebraic reconstruction technique (ART) regularized by total variation (TV), enable accurate reconstructions from sparse-view data, which consequently reduces both scanning time and costs. However, the implementation of the ART-TV is considerably slow, particularly in cone-beam reconstruction. In this paper, we propose an efficient and high-quality scheme for cone-beam CT reconstruction based on the traditional ART-TV algorithm. Our scheme employs Joseph's projection method for the computation of the system matrix. By exploiting the geometric symmetry of the cone-beam rays, we are able to compute the weight coefficients of the system matrix for two symmetric rays simultaneously. We then employ multi-threading technology to speed up the reconstruction of ART, and utilize graphics processing units (GPUs) to accelerate the TV minimization. Experimental results demonstrate that, for a typical reconstruction of a 512 × 512 × 512 volume from 60 views of 512 × 512 projection images, our scheme achieves a speedup of 14 × compared to a single-threaded CPU implementation. Furthermore, high-quality reconstructions of ART-TV are obtained by using Joseph's projection compared with that using traditional Siddon's projection.

Extending the Modified Transverse Crack Tensile test for Mode II Fracture Toughness Characterisation of Hybrid Interfaces

Extending the Modified Transverse Crack Tensile test for Mode II Fracture Toughness Characterisation of Hybrid Interfaces

Crystallography of quasiperiodic moiré patterns in homophase twisted bilayers.

This paper discusses the geometric properties and symmetries of general moiré patterns generated by homophase bilayers twisted by rotation 2δ. These patterns are generically quasiperiodic of rank 4 and result from the interferences between two basic periodicities incommensurate to each other, defined by the sites in the layers that are kept invariant through the symmetry operations of the structure. These invariant sites are distributed on the nodes of a set of lattices called Φ-lattices - where Φ runs on the rotation operations of the symmetry group of the monolayers - which are the centers of rotation 2δ + Φ transforming a lattice node of the first layer into a node of the second. It is demonstrated that when a coincidence lattice exists, it is the intersection of all the Φ-lattices of the structure.

Orthogonality induced by norm derivatives: a new geometric constant and symmetry

Orthogonality induced by norm derivatives: a new geometric constant and symmetry

Impact of Buffer Layer on Electrical Properties of Bow-Tie Microwave Diodes on the Base of MBE-Grown Modulation-Doped Semiconductor Structure

Bow-tie diodes on the base of modulation-doped semiconductor structures are often used to detect radiation in GHz to THz frequency range. The operation of the bow-tie microwave diodes is based on carrier heating phenomena in an epitaxial semiconductor structure with broken geometrical symmetry. However, the electrical properties of bow-tie diodes are highly dependent on the purity of the grown epitaxial layer—specifically, the minimal number of defects—and the quality of the ohmic contacts. The quality of MBE-grown semiconductor structure depends on the presence of a buffer layer between a semiconductor substrate and an epitaxial layer. In this paper, we present an investigation of the electrical and optical properties of planar bow-tie microwave diodes fabricated using modulation-doped semiconductor structures grown via the MBE technique, incorporating either a GaAs buffer layer or a GaAs–AlGaAs super-lattice buffer between the semi-insulating substrate and the active epitaxial layer. These properties include voltage sensitivity, electrical resistance, I–V characteristic asymmetry, nonlinearity coefficient, and photoluminescence. The investigation revealed that the buffer layer, as well as the illumination with visible light, strongly influences the properties of the bow-tie diodes.

Engineering the pore size of interpenetrated metal–organic frameworks for molecular sieving separation of C2H2/C2H4

Interpenetration-regulated pore size engineering is leveraged to fine-tune pore size in interpenetrated Zn-SDBA-dpe/bpy MOFs that creates a discrepancy in geometric symmetry, thus inducing noticeable differences in C2H2/C2H4 separation performances.

Texture-Semantic Point: Registration for Point Clouds of Porcelain Relics

Point cloud models of porcelain are captured through the multi-registration of point clouds, which presents a challenging task. On the one hand, the smooth surface of porcelain lacks geometric feature variation, making it difficult to establish corresponding points. On the other hand, the overall geometric symmetry of most porcelain relics can easily lead to iterative calculations falling into the local minimum convergence trap. To address the difficulties in feature point selection, we propose a novel approach using texture-semantic points as features for coarse registration. We first select rich texture points as 2D candidates and establish a 2D-3D matching relationship, giving each candidate its 3D spatial location and associated texture information. Using these correspondences, we perform coarse alignment of the point clouds. However, in reality, the point clouds are not aligned, and the registration calculation fails because of geometric symmetry issues. To address this, we integrate a control net into the iterative closest point (ICP) calculation to guide iterations towards the correct Special Euclidean group in 3 dimensions (SE(3)) transformation, achieving refined alignment. Finally, considering porcelain’s symmetrical geometry, we introduce a pose optimization constraint using the symmetry axis as a weighted parameter to limit degrees of freedom and enhance registration accuracy. Experiments were conducted on seven porcelain datasets to evaluate the proposed approach. A qualitative analysis demonstrated successful refined alignment using the proposed approach. In addition, we performed a quantitative comparison with state-of-the-art methods. Experimental results showed that our approach outperformed others across all models when applied to the registration of geometrically symmetric porcelain; Specifically, the proposed method achieved a 50% enhancement in accuracy compared with others, measured by the distance between the labeled corresponding points. Paper-related resources are available at https://github.com/tnl-wcz/TSP_ICP.git.

A Two‐Stage CNN‐Based Method for Enhanced Metastasis Segmentation in SPECT Bone Scans

Accurate segmentation of metastatic lesions is crucial for improving the quality of patient care, particularly in the context of bone scans. However, existing automated methods, which are predominantly data‐driven, exhibit limited performance and lack interpretability. To address these challenges, we propose a novel two‐stage framework that integrates human domain knowledge with data patterns to enhance CNN‐based metastasis lesion segmentation in bone scans. The proposed method comprises two phases: Stage I detects hotspots in bone scans using a CNN‐based model, while Stage II identifies actual metastases by leveraging clinical knowledge of uptake intensity asymmetry. Our approach incorporates a dual‐sampling scheme inspired by diagnostic patterns and an enhanced feature extractor within the hotspot segmentation network, thus augmenting the detection capabilities of traditional data‐driven CNN models. The assessment of symmetrical uptake intensity starts with the symmetry axis of the trunk in the image, followed by a composite similarity measure that considers both geometric symmetry and intensity consistency. Experimental evaluations on 302 clinical cases reveal that our proposed segmentation network improves the Dice similarity coefficient score by 4.34% compared to the baseline method. Furthermore, integrating clinical knowledge significantly reduces false positives, improving the class pixel accuracy score by 2.39% and demonstrating notable adaptability to other segmentation models. Comparative analysis with existing models for metastasis lesion segmentation demonstrates the superior performance of our approach. By incorporating domain knowledge into data patterns, our method enhances automated segmentation performance and bridges the gap between domain expertise and data‐driven methodologies in the automated analysis of low‐resolution bone scans.

Coupled acoustoplasmonic resonators: the role of geometrical symmetries.

Acoustoplasmonic resonators, such as nanobars and crosses, are efficient acousto-optical transducers. The excitation of mechanical modes in these structures strongly depends on the spatial profile of the eigenmodes of the resonator. Using a system of two identical gold elongated bars placed on a silicon dioxide substrate, we examine how breaking mirror symmetries affects the optical and acoustic properties to provide insights in the design of acoustoplasmonic metasurfaces for nonsymmetric acousto-optical transducers. Our findings show that the absence of mirror symmetries affects differently the optical and nanomechanical response. Broken mirror symmetries not only couple nanomechanical modes existing in single bars but introduce new torsional resonant modes.

Intermolecular interaction of Al8O12 oxymetallic clusters in the detection of atmospheric pollutants: a DFT exploration of CO, CO2, H2, N2, NO, NO2, O2, and SO2, binding mechanisms.

Due to the lack of inherent geometric symmetry present in the structures of aluminum oxide clusters, determining their stable configuration becomes an exceedingly formidable task computationally. In this comprehensive analysis, we first propose the most stable state of Al8O12, determined through Density Functional Theory calculations at ωB97XD/Def2-TZVP level of theory. Multiple structural isomers were scrutinized for their stability and spin state, with the optimal structure determined using the bee colony algorithm for global optimization. Furthermore, we investigated the intermolecular interactions between various atmospheric gases (CO, CO2, H2, N2, NO, NO2, O2, and SO2) and this oxymetallic cluster. The interactions were evaluated through adsorption energy (E ads) calculations and characterized using multiple analytical frameworks: quantum theory of atoms in molecules, total density of states, natural bond orbital analysis (including bond orders, natural charges, and natural electron configurations), and non-covalent interaction analysis with reduced density gradient. The findings reveal robust interactions between the gas molecules and the cluster structure, with the cluster exhibiting remarkable potential for monitoring various atmospheric gases. Adsorption energy calculations reveal a decreasing trend in binding strength for various gases on the Al8O12 cluster, with values of SO2 (-1.283 eV) > CO (-0.669 eV) > CO2 (-0.579 eV) > NO2 (-0.573 eV) > O2 (-0.521 eV) > NO (-0.486 eV) > N2 (-0.432 eV) > H2 (-0.239 eV), indicating the cluster's potential for selective gas adsorption in applications like sensing and environmental monitoring. The calculated adsorption energies suggest this cluster holds great promise for the development of gas sensing and removal devices, particularly for environmental monitoring applications.

Asymmetric self-organization from a symmetric film by phase separation.

Self-organization realizes various nanostructures to control material properties such as superconducting vortex pinning and thermal conductivity. However, the self-organization of nucleation and growth is constrained by the growth geometric symmetry. To realize highly controlled three-dimensional nanostructures by self-organization, nanostructure formation that breaks the growth geometric symmetry thermodynamically and kinetically, such as tilted or in-plane aligned nanostructures, is a challenging issue. A vertically aligned nano-checkerboard is typically formed from ZnMnGaO4 with the twin domain vertically aligned by the stress from the MgO substrate. The change in the template structure is promising to form a different type of nanostructure. The cubic ZnMnGaO4/MgO films were annealed to form nanoscale tetragonal domains in the tilted direction from the surface, which is determined by lattice mismatch, lattice symmetry, and atomic bonding. On the other hand, as a result of free deformation, in-plane aligned twin domains were formed on the SrTiO3 substrate with a thin MgO buffer layer, which does not induce stress in the ZnMnGaO4 film. By annealing the ZnMnGaO4/MgO/SrTiO3 film, the nano-checkerboard with a size of ∼10 nm and a length of ∼200 nm is elongated to the in-plane [100] or [001] direction. This study demonstrates the possibility of fabricating a nanostructure that breaks the growth geometric symmetry, which is not achieved by the previous self-organization. The phase separation with controlled template opens more complicated three-dimensional structures by self-organization.

Quasiclassical approximation does not have to be applied to all degrees of freedom: the solution for the S-states of singular attractive potentials

For the spherically symmetric potentials V(r), the quasiclassical approximation (QA) usually is applied as follows. For the φ-motion, the QA is not applied: instead, the exact solution is used. The QA is then applied to both the θ-motion and the r-motion. The resulting QA wave function for the θ-motion is valid for some, but not all values of θ. Besides, the resulting QA wave function for the θ-motion is valid only with the substitution of L(L+1) by (L+1/2)2, where L is the angular momentum quantum number. Then the QA is applied to the r-motion, but again with the substitution of L(L+1) by (L+1/2)2 in the centrifugal energy term. As a result of the above standard procedure, the obtained QA wave functions are valid only for (L + 1/2) greater or of the order of N1/2, where N is the principal quantum number. Besides, for potentials having the pole of the order 3 or higher at r = 0 or for relatively large r, it would be preferable to have L(L + 1) without the substitution by (L+1/2)2. This is yet another restriction of the QA validity in this procedure. In the first part of the present paper, we provide a better alternative. This alternative can also be applied to some potentials whose geometrical symmetry is not spherical. In the second part of the present paper, we focus on the attractive singular spherically-symmetric potentials V(r) =-an/rn, where an > 0 and the integer n > 2. They are encountered in many physical systems. There exists a paradigm that “singular attractive potentials do not lead to physically reasonable results” because eigenfunctions depend on the chosen cutoff at small r. In the present paper we disprove this paradigm. We demonstrate that while the unnormalized eigenfunctions of singular attractive potentials do depend on the cutoff at small r, there is no such problem for the corresponding normalized eigenfunctions. Namely, the normalized eigenfunctions, corresponding to any two different sufficiently small cutoffs (all other parameters being the same), are equal to each other or differ just by the sign. The sign difference does not affect the probability density: the latter is invariant to the variations of the cutoff. Thus, we prove that singular attractive potentials actually do lead to physically reasonable results. In doing so, we also demonstrated that a divergent integral can lead to physically meaningful results independent of the cutoff. This is a counterintuitive result of the importance from the fundamental point of view both for physics and mathematics.

Conjugated Heat Transfer of the stator of an synchrounous electrical machine

Electrical energy generation in remote islands and ships are mainly due the energy conversion from chemical (fuel) to mechanical by an engine and converted from mechanical to electrical by an alternator. The losses in the alternator during the energy conversion are responsible for the increase of its temperature. In order to control the temperature level of the equipment, it is necessary to control how heat is evacuated. The present work numerically evaluates the heat dissipation in the stator of an electrical machine and its temperature maximum levels. Heat is generated in the cooper (windings) and steel (stator main body) during the energy conversion and is evacuated due the forced airflow throughout the stator. In order to reduce computational costs, due geometrical symmetry, one quarter of the machine was modeled. In addition to symmetry, the momentum boundary conditions consist in inlet, outlet and noslip at the walls and the thermal boundary conditions consist in imposed heat fluxes. In order to isolate the inlet and outlet boundary conditions, they were positioned at least 10 times the respective channel height far from the stator. The model is transient and the initial flow field is at rest (0 m/s) and at ambient temperature (300 K). The geometry was constructed using Salome-Meca software and the mesh was generated using the snappyHexMesh solver from OpenFOAM v11. The foamMultiRun solver from OpenFOAM was employed to create the numerical model. It solves the mass, momentum and energy equations in transient regime. The numerical schemes employed were linearUpwind (second order) for the advective terms, Gauss for the diffusive terms (linear) and the backward time discretization (second order). The turbulence model employed was the K-omega SST. The model predicted where were the regions inside the stator with intese heat transfer, which implies in lower temperature magnitudes and also where there were temperature peaks. Then correlation between the temperature and flow fields were discussed.