Optimal Orientation Research Articles

Combined effect of piezoelectric, elastic, dielectric, and electro-optical properties on single-domain potassium tantalate niobate single crystals

The complete matrix parameters of the elastic, dielectric, and piezoelectric constants of high-quality Fe-doped KTa1-xNbxO3 (KTN) single crystals poled along [001]PC were successfully confirmed. The piezoelectric coefficients d33 and k33, which are of interest for various applications, are 137 pC/N and 50.4 %, respectively. The orientation dependence of these properties for the single-domain Fe:KTN samples was calculated, and it was found that the [001]PC direction is the optimal orientation for the highest performance with a single-domain state, at which the sample exhibits good transparency. Further, the single-domain sample exhibits a large effective electro-optical coefficient (γc = 126.6 p.m./V), and the combined piezoelectric and electro-optical effects provide a 0.4 % electro-optical coefficient. This is beneficial for applying high-response speed modulators with an effective electro-optical working mode and a low contribution of the inverse piezoelectric effect, owing to slower frequency response characteristics.

Elastic buckling analysis and optimization of thin-walled bamboo-like pipe beam subjected to pure bending

In this paper, a stiffening design imitating the bamboo node is proposed for weight reduction of the long composite pipe beam subjected to bending load. The distribution of bamboo nodes can efficiently suppress the ovalization of the section, thus significantly improving the bending resistance of the bamboo. Based on this principle, ring stiffeners are proposed to be fixed to the pipe beam, making the long beam equivalent to the combination of a series of short pipes that suffered less section ovalization. A database of the optimal laminate orientations for different normalized lengths is obtained through optimizations, where the discreteness of the ply count is considered. Based on this database, weight optimizations are conducted, and the optimal designs of beams with and without stiffeners are obtained and compared. The comparison results show that the proposed bamboo-like stiffened beam not only regains a near-linear load–displacement relationship, but also reduces the weight by up to 16% under the same buckling load. In addition, it is found that for the pipe beams with radius-to-thickness ratios of more than 18, increasing the radius leads to a decrease in elastic buckling resistance when the weight remains a constant, which is opposite to the design for strength and stiffness. The model and database developed in this paper can provide a reference for weight reduction design and weight estimation for composite pipe beams.

Solidification behavior of Sn crystals − Under different temperature gradients

Lead-free solder alloys typically comprise β-Sn, known for its anisotropy. Our experiments revealed that under standard solidification conditions （Room temperature cooling）, characterized by an angular distribution spanning 20–60°, β-Sn crystals exhibited minimal nucleation and lacked a distinct optimal orientation. However, when a temperature gradient of 295 K/cm was applied during the solidification of β-Sn crystals, a conspicuous selective orientation emerged. This orientation favored the growth along the [110] grain axis. However, with the further increase in temperature gradient, a significant transition occurs in the growth mechanism of Sn crystals: multiple nucleation centers emerge, leading to dendritic crystal growth. With the further increase in temperature gradient, a significant transformation occurs in the growth mechanism of Sn crystals: multiple-nucleation centers emerge, leading to dendritic crystal growth, and subsequently transitioning towards equiaxed growth. Consequently, the expansion of the temperature gradient results in an increase in undercooling, triggering a series of changes in crystal growth patterns: the solidification front transitions from planar to dendritic growth and further to equiaxed growth. This is because, with the increasing prominence of undercooling, the transport of solutes from the tin solution to the tin melt diminishes. The atomic saturation in the tin melt decreases, causing a decline in the grain growth rate and promoting the formation of equiaxed crystals.

Learn to Rotate: Part Orientation for Reducing Support Volume via Generalizable Reinforcement Learning

In design for additive manufacturing, an essential task is to determine the optimal build orientation of a part according to one or multiple factors. Heuristic search is used by the most part orientation methods to select the optimal orientation from a large solution space. Search algorithms occasionally converge towards the local optimum and waste considerable time on trial and error. The above issues could be addressed if there was an intelligent agent that knew the optimal search/rotation path for a given 3D model. A straightforward method to construct such an agent is reinforcement learning (RL). By adopting this idea, the time-consuming online searches in existing part orientation methods will be moved to the offline learning stage, potentially improving part orientation performance. This is a challenging research problem because the goal is to build an agent capable of rotating arbitrary 3D models, whereas RL agents frequently struggle to generalize in new scenarios. Therefore, this paper suggests a generalizable reinforcement learning (GRL) framework to train the agent, and a GPU-accelerated GRL benchmark to support the training, testing, and comparison of part orientation approaches. Experimental results demonstrate that the proposed part orientation method on average outperforms others in terms of effectiveness and efficiency. It is proved to have the potential to solve the local minima problems raised in the existing approaches, to swiftly discover the global (sub-)optimal solution (i.e. on average 2.62x to 229.00x faster than the random search algorithm), and to generalize beyond the environment in which it was trained.

Tri-axial rubidium and helium optically pumped magnetometers for on-scalp magnetoencephalography recording of interictal epileptiform discharges: a case study

Cryogenic magnetoencephalography (MEG) enhances the presurgical assessment of refractory focal epilepsy (RFE). Optically pumped magnetometers (OPMs) are cryogen-free sensors that enable on-scalp MEG recordings. Here, we investigate the application of tri-axial OPMs [87Rb (Rb-OPM) and 4He gas (He-OPM)] for the detection of interictal epileptiform discharges (IEDs). IEDs were recorded simultaneously with 4 tri-axial Rb- and 4 tri-axial He-OPMs in a child with RFE. IEDs were identified visually, isolated from magnetic background noise using independent component analysis (ICA) and were studied following their optimal magnetic field orientation thanks to virtual sensors. Most IEDs (>1,000) were detectable by both He- and Rb-OPM recordings. IEDs were isolated by ICA and the resulting magnetic field oriented mostly tangential to the scalp in Rb-OPMs and radial in He-OPMs. Likely due to differences in sensor locations, the IED amplitude was higher with Rb-OPMs. This case study shows comparable ability of Rb-OPMs and He-OPMs to detect IEDs and the substantial benefits of triaxial OPMs to detect IEDs from different sensor locations. Tri-axial OPMs allow to maximize spatial brain sampling for IEDs detection with a limited number of sensors.

Effect of polyethylene fiber orientation on fracture resistance of endodontically treated premolars

Polyethylene fibers have been reported to improve the fracture resistance of endodontically treated teeth, but their optimal orientation is unclear. The purpose of this in vitro study was to evaluate the effects of different fiber positions and orientations on the fracture resistance of endodontically treated premolar teeth. One hundred endodontically treated maxillary premolars were divided into 2 groups according to the cavity design, mesio-occluso-distal and occluso-buccal, and each group was divided into 5 subgroups (n=10) according to the polyethylene fiber orientation on the pulpal floor: unidirectional horizontal (from mesial to distal), unidirectional vertical (from buccal to palatal), bidirectional (buccopalatal and mesiodistal), circular (around the walls), and without fibers (control group). The cavities were restored with fiber-reinforced composite resin and conventional composite resin. All the teeth were fractured with a universal testing machine and analyzed as catastrophic failure or reparable failure. A 1-way ANOVA was used to compare fracture strength values (α=.05). The tested groups with different fiber orientations showed significantly higher fracture load than the control group (P<.05). No statistically significant difference was observed among the fiber orientations (P>.05). Most of the favorable fractures were occlusal to the cemento-enamel junction, and adhesive failure were seen in the mesio-occluso-distal and occluso-buccal cavities. The highest percentage of unfavorable fractures and mixed failures was observed in the control group. The fiber orientation pattern in the mesio-occluso-distal and occluso-buccal cavities did not differ significantly in the fracture resistance of endodontically treated maxillary premolar teeth.

High‐Angle Active Conjugate Faults in the Anza‐Borrego Shear Zone, Southern California

AbstractOrientations of active antithetic faults can provide useful constraints on in situ strength of the seismogenic crust. We use LINSCAN, a new unsupervised learning algorithm for identifying quasi‐linear clusters of earthquakes, to map small‐scale strike‐slip faults in the Anza‐Borrego shear zone, Southern California. We identify 332 right‐ and left‐lateral faults having lengths between 0.1 and 3 km. The dihedral angles between all possible pairs of conjugate faults are nearly normally distributed around 70°, with a standard deviation of ∼30°. The observed dihedral angles are larger than those expected assuming optimal fault orientations and the coefficient of friction of 0.6–0.8, but similar to the distribution previously reported for the Ridgecrest area in the Eastern California Shear Zone. We show that the observed fault orientations can be explained by fault rotation away from the principal shortening axis due to a cumulated tectonic strain.

Chatter Avoidance by Spindle Speed and Orientation Planning in Five-Axis Ball-End Milling of Thin-Walled Blades

Abstract Selecting suitable cutting conditions is crucial in maintaining chatter stability and achieving acceptable surface quality. However, the selection of a constant set of cutting parameters is not feasible due to the time-varying dynamics of highly flexible thin-walled blades. This paper presents an optimal selection of tool orientation and spindle speed along the tool path as the metal is removed during the ball-end milling of blades. The effects of tool orientation and speed on the mechanics and dynamics of the ball-end milling process are formulated. Test case simulations are used to demonstrate the impact of tool orientation and speed on chatter stability and forced vibrations. The proposed algorithm identifies the optimal spindle speed and tool orientation by continuously updating the workpiece dynamics as a function of time and tool position to achieve improved stability and surface quality. Stability simulations are conducted to assess the optimization approach's performance, and the results are compared with experiments by machining a series of thin-walled twisted fan blades.

Optimum orientation of compact and elongated hexadecapole deformed actinide targets: Application to synthesizing superheavy nuclei

Optimum orientation of compact and elongated hexadecapole deformed actinide targets: Application to synthesizing superheavy nuclei

Enhancing Sustainability in Building Design: Hybrid Approaches for Evaluating the Impact of Building Orientation on Thermal Comfort in Semi-Arid Climates

The evaluation of human thermal comfort inside buildings plays a pivotal role in reducing energy consumption and enhancing sustainability in the built environment. The estimation of thermal comfort is based on objective (physical factors) and subjective (psychological factors) aspects. This study aimed to find a hybrid way to evaluate more accurate thermal comfort in the buildings as per their orientations. This study assessed the effect of building orientation on thermal comfort conditions in row houses in semi-arid climates, based on a synthesis of the predictive mean vote (PMV) model and the thermal sensation vote (TSV). For this purpose, row houses were selected in the region of this study. This study concluded that the PMV model calculates a lower thermal comfort level than the TSV method, and that the thermal comfort demand within the houses was higher than ASHRAE Standard 55. The occupants inside the houses had a lower thermal tolerance. This implied that the residents of these buildings can consume more energy during the summer, typically the harshest season. This study presented new mathematical models for occupants’ thermal comfort evaluation in the study region, depending on the building’s orientation. In both models, for assessing thermal performance during both the summer and winter seasons, east-facing buildings consistently ranked as the second-best orientation. This suggested that, overall, east-facing buildings can be considered the best choice throughout the entire year in terms of thermal comfort. This study suggested a novel indicator to evaluate the optimum building orientation in the study area in terms of thermal performance.

Comparative analysis of lithium niobate and barium titanate material platforms for implementing electro-optically tunable general-purpose photonic processors

The field of general-purpose photonic processors (GPPPs) has been gaining momentum as a promising area for reconfigurable integrated photonic hardware. Among various tuning mechanisms, the electro-optic tuning mechanism can enable the implementation of high-speed GPPPs with faster reconfiguration, larger bandwidth, and reduced dependence on high-performance blocks. Lithium niobate (LN) and barium titanate (BTO) are promising electro-optic platforms that enable electro-optically tunable GPPPs. However, the inherent anisotropy associated with the two materials and polarization domain formation in BTO makes the study and analysis of these effects on device performance essential, as GPPPs involve tunable devices in three different orientations, which must perform similarly. This article explores and comparatively analyzes the potential of using two material platforms to enable the implementation of high-speed GPPPs. Various applications implemented on LN and BTO GPPPs are also discussed and compared. Based on our results, a method to select the optimal device orientation for implementing a high-speed GPPP with all devices performing similarly in the two platforms has been proposed. The results indicate that both platforms have their own pros and cons, and the choice of platform depends on the application.

An iso-contour method for automated fiber placement optimization of composite structures

A new method for numerical optimization of fiber-steered composites is presented, which allows to control efficiently and effectively the curvature of the fibers of single- or multi-layer composite structures. It is based on the introduction of an artificial surface defined and controlled by a relatively small number of control points, which is optimized to identify optimal fiber orientations varying smoothly over the panels. Curvature constraints like the maximum fiber curvature constraint, MFCC, or the average fiber curvature constraint, AFCC, are respected explicitly by the method to ensure manufacturability of the composite component. Three validation cases are regarded where results of the unconstrained case are compared to those of established methods to illustrate the validity of the new approach. They are complemented by results considering curvature constraints showing that optimal structures depend strongly on the chosen curvature thresholds. Finally, a rib optimization of a wingbox structure is realized as a more complex case.

Criteria for determining the optimal orientation of rehabilitation measures in children with the consequences of cerebral palsy

Criteria for determining the optimal orientation of rehabilitation measures in children with the consequences of cerebral palsy

Functional lung avoidance in radiotherapy using optimisation of biologically effective dose with non-coplanar beam orientations

Background and purposeIn external beam radiotherapy for non-small cell lung cancer, dose to functioning lung should be minimised to reduce lung morbidity. This study aimed to develop a method for avoiding beam delivery through functional lung and to quantify the possible benefit to the patients. Materials and methodsTwelve patients that were treated as part of a clinical trial of single photon emission computed tomography (SPECT) functional lung avoidance were retrospectively studied. During treatment planning, the dose in the lung was weighted by the relative intensity of the functional image. A single conformal beam was scanned systematically around the planning target volume to find optimum orientations and the resulting map of functional dose variation with gantry and couch angle was used to select five non-coplanar intensity-modulated beams, taking into account directions prohibited due to collision risk. Expected reduction in pneumonitis risk was calculated using a logistic model. ResultsThe volume of lung irradiated to a functionally weighted dose of 5 Gy was 11.8 % (range 3.5 %–22.0 %) for functional plans, versus 20.9 % (range 4.9 %–33.3 %) for conventional plans (p = 0.002). Mean functionally weighted dose was 4.1 Gy (range 1.3 Gy-7.2 Gy) for functional plans, versus 4.5 Gy (range 1.5 Gy-8.3 Gy) for conventional plans (p = 0.002). Predicted pneumonitis risk was reduced by 4.3 % (range 0.4 %-15.6 %) (p = 0.002). ConclusionsBy seeking the optimum non-coplanar beam orientations, it is possible to reduce dose/volume lung parameters by 10% or more, consistently in all patients, regardless of the pattern of lung perfusion. A prediction model indicates that this will improve radiation-associated lung injury.

Investigation on overall energy performance of a novel multi-functional PV/T window

PV windows are considered to be a promising building-integrated PV technology due to their excellent electrical, daylighting and thermal performance. However, the shading of the PV cells increases the heating load in winter and the high temperature of PV cells exacerbates the cooling load in summer. Moreover, a significant portion of the heat absorbed by the PV modules is usually wasted. To address these issues, this paper proposed a multi-functional PV/T window. This system could recover the heat on PV cells for producing warm air in winter and hot water in other seasons. As a result, the proposed system can realize the combined PV/T utilization of solar energy and reduce the seasonal thermal needs of the building. First, the mathematical model of the proposed window was developed and validated. Next, the developed model was integrated into building energy software to evaluate the overall energy performance of the proposed window in four different cities of Yangtze River region: Shanghai, Nanjing, Wuhan, and Chongqing in China. These cities experience the subtropical humid climate (Cfa in the Köppen-Geiger classification) and belong to the zones with medium global horizontal irradiation. The sensitivity analysis revealed that the optimal slat angles are between 0o and 40o, while the optimal orientation angles range from 30o to 60o. Selecting low-iron glass as the inner glass resulted in the lowest overall energy consumption. By adopting the MFPV/T window, the annual operation cost of the studied case could be reduced by 34% (6.4 $/m2), 36% (7.0 $/m2), 28% (5.7 $/m2), and 16% (2.9 $/m2) in these four cites, respectively. Additionally, the annual CO2 emissions could be curtailed by 53.5, 58.5, 47, and 22.3 kg/m2, respectively.

Optimal Orientation Angle Configuration of Polarizers Exists in a 3 × 3 Mueller Matrix Polarimeter

A 3 × 3 Mueller matrix polarimeter, as one of the primary polarization measurement tools, has attracted intensive interest in various fields of polarization optics. In this paper, from a novel viewpoint with more mathematical analysis of the basic configuration and the working performance of a 3 × 3 Mueller matrix polarimeter, we systematically study the relationship between Mueller matrix measurement errors with the configuration and characteristics of polarizers in the polarimeter. We figure out that, mathematically, there is an optimal orientation angle configuration (0°, 60°, and 120°) of polarizers, which inherently ensures a minimal relative measurement error in general. Moreover, we interpret the internal source of such a robust error resistance under this optimized configuration mathematically for the first time. Simulation and practical experiments show the effectiveness of our mathematical analyses, and compared to the frequently used orientation angle configuration, the average relative error is reduced by up to 32% under such an optimized configuration.

Optimal design of stand-alone photovoltaic system based on battery storage system: A case study of Borj Cedria in Tunisia

This work deals with the optimal design of a stand-alone photovoltaic system (SAPS) based on the battery storage system and assesses its technical performance by using PVsyst simulation. In fact, this study is carried out to determine the optimal orientation and tilt angle of a solar panel for collecting maximum solar radiation. Borj Cedria is taken as a case study site to perform the optimum tilt angle through PVsyst. PV-GIS is utilized to estimate global solar irradiance. The proposed system can produce 1314 kWh of energy for the load, which is considered technically suitable for this area thanks to a performance ratio of 58.3% and high specific efficiency generation, besides the solar fraction of about 92.5%. From an economic point of view, the SAPS can save more than 44,000 Dt per year by purchasing energy from the grid system, while considering the aspect of sustainability, 66.24 kg of CO2 annually can be avoided by utilizing the sun’s energy. Furthermore, efficient solar panel use requires its characteristics to be identified under various conditions. An original experimental setup is carried out in the LPV Lab to identify PV characteristics. Experimental and simulation results performed under PSIM software are in good agreement, which shows the experimental setup’s effectiveness.

Modelling Weather Precipitation Intensity on Surfaces in Motion with Application to Autonomous Vehicles.

With advances in the development of autonomous vehicles (AVs), more attention has been paid to the effects caused by adverse weather conditions. It is well known that the performance of self-driving vehicles is reduced when they are exposed to stressors that impair visibility or cause water or snow accumulation on sensor surfaces. This paper proposes a model to quantify weather precipitation, such as rain and snow, perceived by moving vehicles based on outdoor data. The modeling covers a wide range of parameters, such as varying the wind direction and realistic particle size distributions. The model allows the calculation of precipitation intensity on inclined surfaces of different orientations and on a circular driving path. The modeling results were partially validated against direct measurements carried out using a test vehicle. The model outputs showed a strong correlation with the experimental data for both rain and snow. Mitigation strategies for heavy precipitation on vehicles can be developed, and correlations between precipitation rate and accumulation level can be traced using the presented analytical model. A dimensional analysis of the problem highlighted the critical parameters that can help the design of future experiments. The obtained results highlight the importance of the angle of the sensing surface for the perceived precipitation level. The proposed model was used to analyze optimal orientations for minimization of the precipitation flux, which can help to determine the positioning of sensors on the surface of autonomous vehicles.

A unified path seeking algorithm for IMRT and IMPT beam orientation optimization

Objective. Fully automated beam orientation optimization (BOO) for intensity-modulated radiotherapy and intensity modulated proton therapy (IMPT) is gaining interest, since achieving optimal plan quality for an unknown number of fixed beam arrangements is tedious. Fast group sparsity-based optimization methods have been proposed to find the optimal orientation, but manual tuning is required to eliminate the exact number of beams from a large candidate set. Here, we introduce a fast, automated gradient descent-based path-seeking algorithm (PathGD), which performs fluence map optimization for sequentially added beams, to visualize the dosimetric benefit of one added field at a time. Approach. Several configurations of 2–4 proton and 5–15 photon beams were selected for three head-and-neck patients using PathGD, which was compared to group sparsity-regularized BOO solved with the fast iterative shrinkage-thresholding algorithm (GS-FISTA), and manually selected IMPT beams or one coplanar photon VMAT arc (MAN). Once beams were chosen, all plans were compared on computational efficiency, dosimetry, and for proton plans, robustness. Main results. With each added proton beam, Clinical Target Volume (CTV) and organs at risk (OAR) dosimetric cost improved on average across plans by [1.1%, 13.6%], and for photons, [0.6%, 2.0%]. Comparing algorithms, beam selection for PathGD was faster than GS-FISTA on average by 35%, and PathGD matched the CTV coverage of GS-FISTA plans while reducing OAR mean and maximum dose in all structures by an average of 13.6%. PathGD was able to improve CTV [Dmax, D95%] by [2.6%, 5.2%] and reduced worst-case [max, mean] dose in OARs by [11.1%, 13.1%]. Significance. The benefit of a path-seeking algorithm is the beam-by-beam analysis of dosimetric cost. PathGD was shown to be most efficient and dosimetrically desirable amongst group sparsity and manual BOO methods, and highlights the sensitivity of beam addition for IMPT in particular.

Power prediction of a Savonius wind turbine cluster considering wind direction characteristics on three sites

The Savonius wind turbine cluster installation significantly impacts its power output in real wind fields. This study aims to investigate the effect of wind conditions on the power output of a Savonius wind turbine cluster and obtain the optimal installation orientation of the cluster in three selected sites. Two-dimension simulations are conducted to evaluate the cluster performance, and a calculation method based on power curves is proposed to evaluate its annual power output. Results showed that the wake effect induced by wind direction is the primary factor leading to the performance decrease of wind turbines. Optimal installation orientations of the cluster at the three selected sites were obtained using the proposed method, and their corresponding power outputs are 1.25, 1.27, and 1.17 times that of the isolated turbine. The wind direction with high wind energy exerts greater effects than that with high wind frequency in determining the optimal installation orientation. The actual wind resource characteristics should be comprehensively considered in determining the optimal installation orientation in practice. This study provides guidance to the cluster installation in real wind conditions and contributes to the advancement of urban wind energy solutions.