Artículos de revistas sobre el tema "Drop sizing methods"
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Löffler-Mang, M., K. D. Beheng y H. Gysi. "Messung von Tropfengrößenverteilungen in Regen — ein Vergleich zweier Meßmethoden". Meteorologische Zeitschrift 5, n.º 4 (18 de septiembre de 1996): 139–44. http://dx.doi.org/10.1127/metz/5/1996/139.
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Lima, João L. M. P. de, Valdemir P. Silva, M. Isabel P. de Lima, João R. C. B. Abrantes y Abelardo A. A. Montenegro. "Revisiting simple methods to estimate drop size distributions: a novel approach based on infrared thermography". Journal of Hydrology and Hydromechanics 63, n.º 3 (1 de septiembre de 2015): 220–27. http://dx.doi.org/10.1515/johh-2015-0025.
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Abstract The infrared thermography has been successfully applied as a tool for high resolution imaging in different hydrological studies. This exploratory experimental study aimed at evaluating the possibility of using infrared thermography to determine the diameter of raindrops. Rain samples are collected on a pre-heated acrylic board, which is exposed to rain during an instant, and thermograms are recorded. The area of the thermal stains (“signatures” of the raindrops) emerging on the board is measured and converted to drop diameters, applying a calibration equation. Diameters of natural raindrops estimated using this technique were compared with laser disdrometer measurements; the Nash-Sutcliffe efficiency coefficient was used for evaluating the match between the resulting histograms of drop size distribution. Results confirm the usefulness of this simple technique for sizing and counting raindrops, although it is unsatisfactory in light rain or drizzle.
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Brkić, Dejan. "Two Iterative Methods for Sizing Pipe Diameters in Gas Distribution Networks with Loops". Computation 12, n.º 2 (1 de febrero de 2024): 25. http://dx.doi.org/10.3390/computation12020025.
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Closed-loop pipe systems allow the possibility of the flow of gas from both directions across each route, ensuring supply continuity in the event of a failure at one point, but their main shortcoming is in the necessity to model them using iterative methods. Two iterative methods of determining the optimal pipe diameter in a gas distribution network with closed loops are described in this paper, offering the advantage of maintaining the gas velocity within specified technical limits, even during peak demand. They are based on the following: (1) a modified Hardy Cross method with the correction of the diameter in each iteration and (2) the node-loop method, which provides a new diameter directly in each iteration. The calculation of the optimal pipe diameter in such gas distribution networks relies on ensuring mass continuity at nodes, following the first Kirchhoff law, and concluding when the pressure drops in all the closed paths are algebraically balanced, adhering to the second Kirchhoff law for energy equilibrium. The presented optimisation is based on principles developed by Hardy Cross in the 1930s for the moment distribution analysis of statically indeterminate structures. The results are for steady-state conditions and for the highest possible estimated demand of gas, while the distributed gas is treated as a noncompressible fluid due to the relatively small drop in pressure in a typical network of pipes. There is no unique solution; instead, an infinite number of potential outcomes exist, alongside infinite combinations of pipe diameters for a given fixed flow pattern that can satisfy the first and second Kirchhoff laws in the given topology of the particular network at hand.
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Cai, Wenlu, Cherdpong Jomdecha, Yingsong Zhao, Li Wang, Shejuan Xie y Zhenmao Chen. "Quantitative evaluation of electrical conductivity inside stress corrosion crack with electromagnetic NDE methods". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, n.º 2182 (14 de septiembre de 2020): 20190589. http://dx.doi.org/10.1098/rsta.2019.0589.
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This paper presents a comparison of studies on the local distributed electrical conductivity in stress corrosion crack (SCC) from signals of eddy current testing (ECT) and direct current potential drop (DCPD) aiming to improve SCC sizing accuracy when using electromagnetic non-destructive testing (NDT) methods. Experimental setups of ECT and DCPD were established, respectively, to collect measurement signals due to artificial SCCs in a plate of austenitic stainless steel. The local conductivity in the SCC region was reconstructed from the feature parameters extracted from the measured ECT and DCPD signals through inverse analyses. The inversion strategies for ECT and DCPD, each including an efficient forward simulation and an optimization scheme, were introduced from the viewpoint of conductivity reconstruction. Inversion results obtained from the measured ECT and DCPD signals showed the consistent trend which proved the validity of the predicted electrical conductivity indirectly. It is clarified that the electrical conductivity in a SCC is relatively high at the crack tip area and may become as high as 17% of that of the base material. These results provide a good reference to enhance the sizing accuracy of SCC with an electromagnetic NDT method such as ECT by updating the conductive crack model based on the results of this work. This article is part of the theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’.
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Singleton, E. W. "Development of a High-Performance Choke Valve with Reference to Sizing for Multiphase Flow". Measurement and Control 24, n.º 9 (noviembre de 1991): 273–81. http://dx.doi.org/10.1177/002029409102400902.
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The paper describes events leading up to the development of a variable choke valve for high-pressure drop service on multiphase fluids. During the evolvement of the design, which has now been proved in service, it was found necessary to discard some of the accepted precepts and conventions of control valve design. This work also led to an investigation into the various methods of sizing valves for multiphase fluids. The results obtained from available methods were compared and a new method was devised which appears to maintain a higher level of accuracy over a wide range of multiphase flow conditions.
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Satyarnarayan, L., D. M. Pukazhendhi, Krishnan Balasubramaniam, C. V. Krishnamurthy y D. S. Ramachandra Murthy. "Phased Array Ultrasonic Measurement of Fatigue Crack Growth Profiles in Stainless Steel Pipes". Journal of Pressure Vessel Technology 129, n.º 4 (24 de julio de 2006): 737–43. http://dx.doi.org/10.1115/1.2767367.
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This paper reports experimental sizing of fatigue crack profiles that are initiated from artificially made circumferential starter notches in stainless steel pipes of 169mm outer diameter and 14.33mm thickness, which were subjected to cyclic bending loads in a four point bending load arrangement using two nondestractive evaluation (NDE) methods: (a) phased array ultrasonic technique and (b) alternating current potential drop technique. The crack growth estimated using the two NDE techniques were compared with the beach marks that were present in the fracture surface. A simulation study using the ray tracing method was carried out to model the ultrasonic wave propagation in the test specimen, and the results were compared with the experimental results.
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Gyürki, Dániel, Benjamin Csippa, György Paál y István Szikora. "Impact of Design and Deployment Technique on the Hydrodynamic Resistance of Flow Diverters". Clinical Neuroradiology 32, n.º 1 (22 de octubre de 2021): 107–15. http://dx.doi.org/10.1007/s00062-021-01106-1.
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Abstract Purpose Despite the high efficacy of flow diverters (FD) in treating sidewall intracranial aneurysms, failures are reported. One of the physical factors determining efficacy is the flow reducing capacity of the FD that is currently unknown to the operator. Our aim was to measure the flow reducing capacity expressed as the hydrodynamic resistance (HR), the metallic surface area (MSA) and pore density (PD) of two different FD designs and quantitatively investigate the impact of sizing and the deployment technique on these parameters. Methods Altogether 38 Pipeline (Medtronic) and P64 (Phenox) FD‑s were implanted in holder tubes by a neurointerventionist in nominally sized, oversized and longitudinally compressed or elongated manners. The tubes were placed in a flow model with the flow directed across the FD through a side hole on the tube. HR was expressed by the measured pressure drop as the function of the flow rate. Deployed length, MSA and PD were also measured and correlated with the HR. Results Both PD and MSA changed with varying deployment length, which correlates well with the change in HR. Oversizing the device by 1 mm in diameter has reduced the HR on average to one fifth of the original value for both manufacturers. Conclusion This study demonstrates experimentally that different FD designs have different flow diverting capacities (HR). Parameters are greatly influenced by radial sizing and longitudinal compression or elongation during implantation. Our results might be useful in procedure planning, predicting clinical outcome, and in patient-specific numerical flow simulations.
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Kalioudjoglou, Loïck, Clément Bonneau, Vincent Melot, Bruno Auvity, Christophe Josset y Yoann Merriaux. "Prediction or hydraulic performance of shell-and-tube heat exchanger: comparison of 1D and CFD-porous media approaches". MATEC Web of Conferences 240 (2018): 02008. http://dx.doi.org/10.1051/matecconf/201824002008.
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The present paper deals with Heat Exchanger sizing methods and offers a comparison between two of them: 1D global method and CFD porous media method. Following Prithiviraj et al. work [1], new developments are based on recent knowledge acquired on porous media, using a coupling strategy of a three-dimensional commercial code with an in-house code library. The distributed hydraulic resistance concept and the numerical model are briefly described and confronted with pressure drop measurements from an experimental E-type STHE setup (shell-and-tube heat exchanger) from the literature. The present paper will put into perspective capabilities and limits of each method with needs for heat exchanger rating. Flow rate repartition is calculated with CFD-porous media using Tinker’s current approach. This new analysis provides a complete comparison with 1D global method. It also reveals the major impact of leakage flow rate between baffle and tubes. The numerical estimation of pressure losses, consistent with experimental measurements of Halle et al. [2], implies that our future work will include thermal performance characterization and geometrical optimization.
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Martinez, Gabrielle L., Farzad Poursadegh, Gina M. Magnotti, Katarzyna E. Matusik, Daniel J. Duke, Benjamin W. Knox, Alan L. Kastengren, Christopher F. Powell y Caroline L. Genzale. "Measurement of Sauter mean diameter in diesel sprays using a scattering–absorption measurement ratio technique". International Journal of Engine Research 20, n.º 1 (19 de diciembre de 2018): 6–17. http://dx.doi.org/10.1177/1468087418819912.
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A new diagnostic for the quantification of Sauter mean diameter in high-pressure fuel sprays has been recently developed using combined optical and X-ray measurements at the Georgia Institute of Technology and Argonne National Laboratory, respectively. This diagnostic utilizes liquid scattering extinction measurements from diffuse back-illumination imaging, conducted at Georgia Tech, and liquid absorption measurements from X-ray radiography, conducted at Argonne’s Advanced Photon Source. The new diagnostic, entitled the scattering–absorption measurement ratio, quantifies two-dimensional distributions of path-integrated Sauter mean diameter, enabling the construction of the spatial history of drop size development within practical fuel sprays. This technique offers unique benefits over conventional drop-sizing methods in that it can be more robust in optically dense regions of the spray, while also providing high spatial resolution of the corresponding droplet field. The methodology for quantification of Sauter mean diameter distributions using the scattering–absorption measurement ratio technique has been previously introduced and demonstrated in diesel sprays using the Engine Combustion Network Spray D injector; however, a more detailed treatment of measurement uncertainties has been needed. In this work, we present a summary of the various sources of measurement uncertainty in the scattering–absorption measurement ratio diagnostic, like those due to the experimental setup, data processing methods, and theoretical assumptions, and assess how these sources of uncertainty affect the quantified Sauter mean diameter. The spatially resolved Sauter mean diameter measurements that result from the scattering–absorption measurement ratio diagnostic will be especially valuable to the engine modeling community for the quantitative validation of spray submodels in engine computational fluid dynamics codes. Careful evaluation and quantification of measurement uncertainties are important to support accurate model validation and to ensure the development of more predictive spray models.
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Grossmann, Wolf, Iris Grossmann y Karl W. Steininger. "Solar electricity supply isolines of generation capacity and storage". Proceedings of the National Academy of Sciences 112, n.º 12 (9 de marzo de 2015): 3663–68. http://dx.doi.org/10.1073/pnas.1316781112.
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The recent sharp drop in the cost of photovoltaic (PV) electricity generation accompanied by globally rapidly increasing investment in PV plants calls for new planning and management tools for large-scale distributed solar networks. Of major importance are methods to overcome intermittency of solar electricity, i.e., to provide dispatchable electricity at minimal costs. We find that pairs of electricity generation capacity G and storage S that give dispatchable electricity and are minimal with respect to S for a given G exhibit a smooth relationship of mutual substitutability between G and S. These isolines between G and S support the solving of several tasks, including the optimal sizing of generation capacity and storage, optimal siting of solar parks, optimal connections of solar parks across time zones for minimizing intermittency, and management of storage in situations of far below average insolation to provide dispatchable electricity. G−S isolines allow determining the cost-optimal pair (G,S) as a function of the cost ratio of G and S. G−S isolines provide a method for evaluating the effect of geographic spread and time zone coverage on costs of solar electricity.
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Li, Yang, Zhenggan Zhou y Jun Wang. "Analysis of Linear Non-Destructive Testing and Evaluation Methods for Thin-Walled Structure Inspection Using Ultrasonic Array". Coatings 9, n.º 2 (22 de febrero de 2019): 146. http://dx.doi.org/10.3390/coatings9020146.
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The ultrasonic array used for thin-walled structure non-destructive inspection usually has a high central frequency so that the thickness-to-acoustic wavelength ratio is greater than 10. When the ratio is much smaller than 10, the reliability of the conventional ultrasonic array method will dramatically decrease due to the influence of the acoustic near-field. This situation is unavoidable since the available central frequency of the array transducer cannot be an arbitrarily large value. To optimize the inspection performance in this case, the testing of an ultrasonic array and the evaluation of a structure whose thickness is smaller than five-times the longitudinal wavelength are analyzed in this paper. Linear ultrasonic array methods using different combinations of wave patterns, reflection times, and coupling conditions are uniformly expressed as full matrix algorithms. Simulated and experimental full matrices of 6 mm-thick aluminum plates using a 5-MHz array transducer are captured to analyze their imaging performances and sizing abilities with respect to various defects. Analyses show that the inspection results of the wedge coupling method have a much higher signal-to-noise ratio (SNR) than the results of conventional direct contact methods. Circular defects and rectangular defects can be distinguished by comparing the imaging results of different modes. For the simulated circular defect, the diameter can be measured according to the maximum image amplitude of the defect. To simulate a rectangular defect located in the lower half of the region, the nominal length can be measured using a linear function whose input is a −6 dB drop in length of the SS-S mode image. For a real sample, the material anisotropy and complex self-reflections will decrease the SNR by about 10 dB.
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Barestrand, Henrik, Anna-Lena Ljung, Jon Summers y Staffan Lundström. "Modeling Convective Heat Transfer of Air in a Data Center Using OpenFOAM". OpenFOAM® Journal 3 (7 de agosto de 2023): 146–58. http://dx.doi.org/10.51560/ofj.v3.59.
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Achieving energy and cooling efficiency in data center convective air flow and heat transfer can be a challenging task. Among different numerical methods to work with such issues is the Finite Volume Method in Computational Fluid Dynamics. This work evaluates the performance of two such solvers provided by OpenFOAM® in solving this type of convective heat-transfer problem, namely BuoyantBoussinesqPimpleFOAM and BuoyantPimpleFOAM. This is done for two different flow configurations of significantly different Richardson number. To sufficiently resolve the flow, grid sizing effects are elucidated by way of the kernel density estimate. It determines the volume distribution of the temperature in the data center configuration. For the k-epsilon turbulence model used here, it was found that the compressible solver performs faster and requires less grid resolution for both flow configurations. This is attributed to the nature of the boundary conditions which are set such that the mass flow conservation per server rack and cooling unit is achieved. Transient solutions are found to provide better iterative convergence for cases that involves buoyancy, compressibility and flow separation. This is, in comparison to steady-state solutions where artificial numerical pressure drop is found, to depend on the momentum relaxation factors for the convective case with a higher Richardson number.
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Liu, Longquan y Wenjun Xu. "A Study on the In-Plane Shear-after-Impact Properties of CFRP Composite Laminates". Materials 15, n.º 14 (20 de julio de 2022): 5029. http://dx.doi.org/10.3390/ma15145029.
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Impact loading on carbon fiber reinforced polymer matrix (CFRP) composite laminates can result in a significant reduction in their residual properties, and the (ShAI) properties of the composite material are essential to obtain the material allowable values of the shear dominated composite structures. In order to obtain the ShAI properties of the composite material in pure shear stress at a coupon level, this study presents theoretical, experimental, and numerical methods and analysis work on the in-plane shear and ShAI properties of the composite laminates. Theoretically, a method of sizing the composite specimen loading in shear is developed through comparing the load values due to buckling and the material failure. Following this, both impact tests using the drop-weight method and ShAI tests using the picture frame test method are conducted, and the influences of the impact energies on the impact damage and the residual ShAI values are evaluated. Moreover, a progressive failure finite element model based on the Hashin’s failure criterion and the cohesive zone model is developed, and a two-step dynamic analysis method is performed to simulate the failure process of the composite laminates under impact loading and ShAI loading. It is found that the impact damage with the cut-off energy, 50 J, causes a 26.8% reduction in the residual strength and the residual effective shear failure strain is about 0.0132. The primary reason of the shear failure is the propagation of both the matrix tensile failure and interlaminar delamination. It can be concluded that the proposed theoretical, experimental, and numerical methods are promising factors to study the ShAI properties of the composite materials.
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Whitehead, Christopher y Courtney Hall. "31 Establishing Pressure Parameters and Viability of a 3D Printed Dynamic Microstomia Prevention Orthosis". Journal of Burn Care & Research 45, Supplement_1 (17 de abril de 2024): 25. http://dx.doi.org/10.1093/jbcr/irae036.031.
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Abstract Introduction Microstomia prevention orthoses (MPOs) are a standard of care for perioral burns to prevent and correct contractures due to hypertrophic burn scar. A simple, cost effective 3D printed MPO was designed with a dynamic middle component and two mouthpieces. Our goal was to establish parameters for providing appropriate pressure and to examine the viability of the design before implementation. Although effective pressure standards for dynamic MPOs have not been established, our objective is 15-25 mmHg based on the current literature for effective pressure therapy of hypertrophic burn scars. Methods Multiple MPOs were fabricated with varying levels of elasticity. Two variables were modified: the length in 1 cm increments (9 cm to 13 cm) and the level of infill by 10% (80% to 100%), resulting in fifteen separate devices. A digital force gauge was used to measure peak force in four positions of compression to determine pressure for the MPOs along the varying levels of mouth opening. Starting with the mouth pieces 1 cm apart, the distance was increased by 1 cm increments (1 cm to 4 cm) and measured. Using the force divided by the surface area of the device, the pressure was calculated. Three of the MPOs that provided consistent pressure through the widest coverage of mouth opening were selected for further testing. Ten duplicates of each of the three MPOs were fabricated and re-tested in the same four positions to assess the precision of the design. Another ten duplicates of each size were measured for force at one-minute intervals for ten minutes with the mouthpieces 2.5 cm apart to assess a decline in elasticity over time. Results The lengths of 10 cm, 11 cm, and 12 cm with 80% infill were selected because they provide coverage from 27.3 mmHg at 1 cm to 21.2 mmHg at 4 cm apart. The mean, standard deviation, and coefficient of variation were calculated to assess precision for all sizes in all four positions. The standard deviation ranged from 0.21 to 0.49 mmHg and was 0.9 % to 2.2% of the mean. When assessing decline in elasticity, the MPOs dropped an average of 3.97 mmHg over a 10-minute period with 76.97% of the decrease occurring within the first three minutes. Conclusions The use of three MPOs of the same infill but different lengths provide sufficient pressure across the various degrees of mouth opening. They demonstrate consistent pressures between orthoses of the same length and infill. While there is an initial drop in pressure after application, the devices continue to provide therapeutic levels of pressure during use. Applicability of Research to Practice These orthoses have been shown to reliably provide pressure and are ready to be incorporated into clinical practice. A sizing chart can be used to select the correct size MPO based on horizontal mouth opening. This simple but effective design has the potential to provide a low cost solution for burn microstomia with worldwide availability.
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DUTTA, ROBI y MALGORZATA MAREK-SADOWSKA. "ALGORITHM FOR WIRE SIZING OF POWER AND GROUND NETWORKS IN VLSI DESIGNS". Journal of Circuits, Systems and Computers 02, n.º 02 (junio de 1992): 141–57. http://dx.doi.org/10.1142/s0218126692000118.
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Distributing power and ground to the elements present in a VLSI chip is a very crucial task in the design process. Power networks carry substantial currents and wires carrying them have to be carefully designed to avoid damage caused by electromigration and should not experience significant voltage drops. This paper presents a fast and efficient method for sizing power/ground networks. No restrictions on network topology or the number of supplying pads are imposed. Wire widths are calculated such that the weighted area of wire segments is minimized while electromigration and voltage drops constraints are fulfilled. The algorithm proposed here runs 50% faster for unrestricted topologies than the best methods reported in literature for tree type networks.
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Bekker, Eric Botha, Daniel J. Holland y Aaron Timothy Marshall. "Electrical Resistive Tomography to Analyse the Flow Behaviour in Redox Flow Batteries". ECS Meeting Abstracts MA2022-01, n.º 48 (7 de julio de 2022): 2016. http://dx.doi.org/10.1149/ma2022-01482016mtgabs.
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Redox flow batteries (RFBs) are re-emerging as a safe, scalable, efficient and versatile means of large-scale energy storage. Growing adoption of renewable energy generation has ushered a new optimism regarding future reduction in fossil fuel dependency; limiting further harm dealt to the climate and wider environment. However, this momentum demands more efficient energy storage solutions to reconcile power demand and the intermittent nature of wind, solar and tidal energy generation [1]. Without proper storage, reliable back-up generation – largely provided by fossil fuels – will continue to be an unavoidable reality [2]. RFBs utilise the electrochemical properties of dissolved metal ions to store and release energy. Independent sizing of electrolyte storage tanks and flexible power delivery contributes to the flexibility of RFBs compared to alternative battery technologies [3]. RFB reactions occur at the electrode-electrolyte interface, and thus the mass transport at this interface is a critical factor in determining the overall RFB performance. Most RFBs use porous electrodes, with a popular choice of material being carbon felt (CF) due to its low cost, chemical stability and high conductivity [4], although the hydrophobic nature of some CF can cause poor electrode ‘wettability’- decreasing the contact area between the electrode and the electrolyte. Further, electrolyte depletion and asymmetric flow can lead to the presence of ‘dead spots’ where the interface is inactive. Many studies have been conducted on CF to improve the electrochemical performance, using surface treatments, compression and channel flow to improve active area, wettability, and species transport [5-7]. These each have direct impact on current density, pressure drop, overpotentials, and energy efficiency. While the flow of electrolyte in the RFB porous electrodes can be modelled using computational fluid dynamics (CFD) [8], and experimentally assessed using x-ray tomography [9,10] and some optical visualisation methods [11], there are limited experimental methods which can be used on entire RFB stacks. In this study, we explore the use of electrical resistive tomography (ERT) to probe the flow of electrolyte through RFB electrodes. ERT has the advantage that it can provide a non-intrusive means of investigating the hydrodynamics of the otherwise opaque cell stack. Measurements were performed using an array of electrodes place around the perimeter of an RFB electrode chamber which contained conventional carbon felt electrodes. Sensitivity maps were generated using the COMSOL Multiphysics platform and compared with experimental measurements. The flow distribution was evaluated by using injections of concentrated KCl solutions into the background electrolyte. Overall, ERT demonstrated promise as a technique for characterising real-time flow dynamics in RFB stacks and for future research into porous electrode and flow field modifications. References [1] Ambec, S., and Crampes, C., Electricity Provision with Intermittent Sources of Energy. Resource and Energy Economics, Elsevier, 2012. 34: p.320-331. [2] Wagner, F., Electricity by intermittent sources: An analysis based on the German situation 2012. The European Physical Journal Plus, Springer, 2014. 129: 20. [3] Wang, W., et al., Recent Progress in Redox Flow Battery Research and Development. Advanced Functional Materials, Wiley, 2013. 23: p. 970-986. [4] Gonzalez-Garcia, J., et al., Characterization of a carbon felt electrode: structural and physical properties. Journal of materials Chemistry, 1999. 9: p. 419-426. [5] Wang, Q., et al., Experimental study on the performance of a vanadium redox flow battery with non-uniformly compressed carbon felt electrode. Applied Energy, Elsevier, 2018. 213: p. 293-305. [6] Wang, S., et al., Nitrogen-Doped Carbon Nanotube/Graphite Felts as Advanced Electrode Materials for Vanadium Redox Flow Batteries. The Journal of Physical Chemistry Letters, ACS Publications, 2012. 3: p. 2164-2167. [7] Kim, K., et al., The effects of surface modification on carbon felt electrodes for use in vanadium redox flow batteries. Materials Chemistry and Physics, 2011. 131: p. 547-553. [8] Oh, k., et al., Three-dimensional, transient, non-isothermal model of all-vanadium redox flow batteries. Energy, Elsevier, 2015. 81: p. 3-14. [9] Eifert, L., et al., Synchrotron X-ray Radiography and Tomography of Vanadium Redox Flow Batteries—Cell Design, Electrolyte Flow Geometry, and Gas Bubble Formation. ChemSusChem, Wiley, 2020. 13: 3154-3165. [10] Trogadas, P., et al., X-ray micro-tomography as a diagnostic tool for the electrode degradation in vanadium redox flow batteries. Electrochemistry Communications, Elsevier, 2014. 48: p. 155-159 [11] Bhattarai, A., et al., Study of flow behaviour in all-vanadium redox flow battery using spatially resolved voltage distribution. Journal of Power Sources, Elsevier, 2017. 360: p. 443- 452.
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Habib, Habib Ur Rahman, Asad Waqar, Sharoze Sohail, Abdul Khalique Junejo, Mahmoud F. Elmorshedy, Sheheryar Khan, Yun-Su Kim y Moustafa Magdi Ismail. "Optimal Placement and Sizing Problem for Power Loss Minimization and Voltage Profile Improvement of Distribution Networks under Seasonal Loads Using Harris Hawks Optimizer". International Transactions on Electrical Energy Systems 2022 (30 de junio de 2022): 1–49. http://dx.doi.org/10.1155/2022/8640423.
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Improving efficiency with sustainable radial distribution networks (RDNs) is challenging for larger systems and small grid-connected RDNs. In this paper, the optimal placement of DGs with the Harris hawks optimizer (HHO) under seasonal load demands is proposed to simultaneously reduce total active and reactive power losses and minimize bus voltage drops with the consideration of operational constraints of RDNs. HHO is a newly inspired metaheuristic optimization algorithm primarily based on the Harris hawks’ intelligent behaviors during the chasing of the prey. Furthermore, the authors have investigated four stages of DGs. The first stage involves the optimal allocation of one DG. The second stage includes an investigation with two DGs, the third stage considers three DGs, and the fourth stage investigates the integration of four DGs. The effectiveness of the applied HHO is validated on IEEE 33 and 69 bus RDNs, and results are analyzed by comparing with the standard optimization methods. The Big-O test is also executed for statistical analysis with standard algorithms. The simulation results reveal the better performance of the applied HHO under different circumstances than other algorithms. Furthermore, the total active and reactive power losses and bus voltage drops are improved by adding more DGs into IEEE 33 and 69 bus RDNs.
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Pabón, Francisco, Esteban Inga y Miguel Campaña. "Planning Underground Power Distribution Networks to Minimize Negative Visual Impact in Resilient Smart Cities". Electricity 3, n.º 3 (16 de septiembre de 2022): 463–79. http://dx.doi.org/10.3390/electricity3030024.
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This paper presents the application of heuristic methods in conjunction with graph theory in the optimal routing and sizing of underground distribution networks in georeferenced (GIS) scenarios, which are modeled and simulated in the advanced engineering tool CYMDIST. The tool allows the deployment of underground networks to facilitate the design, planning, and implementation of networks, taking into consideration distribution company regulations, thus allowing overview and future planning in the growth of distribution systems. Further, this method is modeled in real georeferenced scenarios, where the coverage of the electric service to all users connected to the network is guaranteed according to population density and energy demand while minimizing the number of distribution transformers used. The applied method considers the location of transformer chambers, the capacity and coverage of the distribution transformers, and the voltage drops over the line section, which should not exceed 5% of the nominal value as described in the ANSI C84.1 standard. Consequently, to verify the efficiency of the applied method, the limitations and restrictions of the mathematical model are considered, as well as the characteristics of the georeferenced system and a comparison with different research studies that address the subject presented here. In addition, supply coverage is guaranteed to be 100%.
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Kreishan, Maen Z. y Ahmed F. Zobaa. "Mixed-Integer Distributed Ant Colony Optimization of Dump Load Allocation with Improved Islanded Microgrid Load Flow". Energies 16, n.º 1 (25 de diciembre de 2022): 213. http://dx.doi.org/10.3390/en16010213.
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Dump load (DL) utilization at low demand hours in highly penetrated islanded microgrid is of great importance to offer voltage and frequency regulation. Additionally, load flow (LF) convergence is vital to optimize the working states of the DL allocation problem. Hence, more analysis is necessary to highlight the significance of DL in power regulation while observing the influence of LF on solution accuracy. This article proposes two LF techniques derived from backward/forward sweep (BFS), viz., general BFS (GBFS) and improved special BFS (SBFS-II). The latter is based on global voltage shared between generating units, while the former has a more general approach by considering generating bus’s local voltage. The optimal sizing and sitting of DL with optimum droop sets are determined using the mixed-integer distributed ant colony optimization (MIDACO) with the two new LF methods. The optimization problem was formulated to minimize voltage and frequency deviations as well as power losses. The problem was validated on IEEE 69- and 118-bus systems and compared with established metaheuristics. Results show that DL allocation using MIDACO with SBFS-II and GBFS has improved the solution speed and accuracy, respectively. Furthermore, the enhanced voltage and frequency results highlight DL as an efficient power management solution.
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Abbas, Asad, Saeed Mian Qaisar, Asad Waqar, Nasim Ullah y Ahmad Aziz Al Ahmadi. "Min-Max Regret-Based Approach for Sizing and Placement of DGs in Distribution System under a 24 h Load Horizon". Energies 15, n.º 10 (18 de mayo de 2022): 3701. http://dx.doi.org/10.3390/en15103701.
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Load variations in any power system result in loss escalation and voltage drops. With the sensible and optimal allocation of distributed generators (DGs), these problems could be considerably mitigated. It has been seen in existing methods that, ideally, the allocation of DGs has been carried out during fixed loads and constant power requirements. However, in real scenarios the loads are always variable and the allocation of DGs must be done in accordance with the variations of the connected load. Therefore, the current paper addresses the aforementioned problem by the distinctive optimal allocation of DGs for each variability of 24 h load horizon. However, a single exclusive solution is considered among all allocations of 24 h. The min-max regret concept has been utilized in order to deal with such a methodology. Altogether, 24 scenarios are analyzed wherein each scenario corresponds to a specific hour of the respective day. The optimal allocation of DGs in terms of their optimal sizing and placement has been carried out by using three algorithms including battle royale optimization (BRO), accelerated particle swarm optimization (APSO), and genetic algorithm (GA). The multi-objective optimization problem is evaluated on the basis of minimum value criterion of the multi-objective index (MO). MO comprises active and reactive power losses and voltage deviation. Hence, in order to find the robustness of the proposed technique, Conseil international des grands reseaux electriques’ (CIGRE) MV benchmark model incorporating 14 buses has been used considerably as a test network. In the end, the results of three proposed algorithms have been compared.
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Chen, H. L., S. D. Wilson y T. G. Monger-McClure. "Determination of Relative Permeability and Recovery for North Sea Gas-Condensate Reservoirs". SPE Reservoir Evaluation & Engineering 2, n.º 04 (1 de agosto de 1999): 393–402. http://dx.doi.org/10.2118/57596-pa.
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Summary Coreflood experiments on gas condensate flow behavior were conducted for two North Sea gas condensate reservoirs. The objectives were to investigate the effects of rock and fluid characteristics on critical condensate saturation (CCS), gas and condensate relative permeabilities, hydrocarbon recovery and trapping by water injection, and incremental recovery by subsequent blowdown. Both CCS and relative permeability were sensitive to flow rate and interfacial tension. The results on gas relative permeability rate sensitivity suggest that gas productivity curtailed by condensate dropout can be somewhat restored by increasing production rate. High interfacial tension ultimately caused condensate relative permeability to decrease with increasing condensate saturation. Condensate immobile under gas injection could be recovered by water injection, but more immediate and efficient condensate recovery was observed when the condensate saturation prior to water injection exceeded the CCS. Subsequent blowdown recovered additional gas, but incremental condensate recovery was insignificant. Introduction Reservoirs bearing gas condensates are becoming more commonplace as developments are encountering greater depths, higher pressures, and higher temperatures. In the North Sea, gas condensate reservoirs comprise a significant portion of the total hydrocarbon reserves. Accuracy in engineering computations for gas condensate systems (e.g., estimating reserves, sizing surface facilities, and predicting productivity trends) depends upon a basic understanding of phase and flow behavior interrelationships. For example, gas productivity may be curtailed as condensate accumulates by pressure depletion below the dew point pressure (Pd). Conceptual modeling on gas condensate systems suggests that relative permeability (kr) curves govern the magnitude of gas productivity loss.1,2 Unfortunately, available gas and condensate relative permeability (krg and krc) results for gas condensates are primarily limited to synthetic systems. Such results show that higher CCS and less krg reduction were observed for a conventional gas/oil system compared to a gas condensate system.3,4 If condensate accumulates as a continuous film due to low interfacial tension (IFT), then high IFT gas/oil and water/oil kr data may not be applicable to gas condensates.5 Water invasion of gas condensate reservoirs may enhance hydrocarbon recovery or trap potential reserves. Laboratory results suggest water invasion of low IFT gas condensates may not be represented using high IFT water/oil and water/gas displacements.6 Subsequent blowdown may remobilize hydrocarbons trapped by water invasion. The presence of condensate may hinder gas remobilization, thus conventional gas/water blowdown experiments may not be appropriate in evaluating the feasibility of depressurization for gas condensates.7,8 Other laboratory evaluations of gas condensate flow behavior indicate measured results depend upon experimental procedures, fluid properties, and rock properties.3,9–20 Factors to consider include the history of condensate formation (i.e., imbibition or drainage), how condensate was introduced (i.e., in-situ dropout versus external injection or inflowing gas), flow rate, differential pressure, system pressure, IFT, connate water saturation, core permeability, and core orientation. Experiments performed to evaluate the consequences of water invasion suggest optimum conditions depend upon IFT, initial gas saturation, and core permeability.7,21,22 Reported blowdown experiments imply gas recovery depends upon the degree of gas expansion.7,8 The kr results obtained in this study represent gas condensate flow between the far-field and the near-wellbore region. The results are useful input for numerical simulation, especially to test rate- or IFT-sensitive relative permeability functions. Results on hydrocarbon recovery and trapping from water injection and blowdown are beneficial in evaluating improved recovery options for gas condensates. Experimental Procedures Coreflooding experiments were performed under reservoir conditions using rock and fluid samples from two distinct North Sea gas condensate reservoirs. A detailed description of the experimental methods is provided in the Appendix. Briefly, the experiments were conducted in a horizontal coreflood apparatus equipped with in-line PVT and viscosity measuring devices. The entire system experienced in-situ condensate drop out by constant volume depletion (CVD) from above Pd to either the pressure corresponding to CCS, or to the pressure of maximum condensate saturation Scmax Steady-state krg was measured by injecting equilibrated gas (before CCS). Steady-state krg and krc were measured by injecting gas condensate repressurized to above Pd (after CCS). The gas/oil fractional flow rate was defined by the pressure level in the core which was controlled by the core outlet back-pressure regulator. During krg measurements, the injection rate was varied to access rate effects. After the krg or krg and krc measurements to Scmax were completed, water injection was performed to quantify hydrocarbon trapping and recovery. Blowdown followed to evaluate additional hydrocarbon recovery. Recombined Reservoir Fluid Properties. Two North Sea gas condensate reservoir fluids were recombined using separator oil and synthetic gas. Tables 1 and 2 list compositions and PVT properties for the reconstituted fluids. The Pd was 7,070 psig at 250°F for Reservoir A, and 6,074 psig at 259°F for Reservoir B (Table 2). The maximum liquid dropout under constant composition expansion (CCE) was 31.7% for Reservoir A, and 42.5% for Reservoir B (Fig. 1). Reservoir B is a richer gas condensate and exhibits more near-critical phase behavior than Reservoir A.
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Jensen, Jørgen B., Stuart P. Beaton, Jeffrey L. Stith, Karl Schwenz, Marilé Colón-Robles, Robert M. Rauber y John Gras. "The Giant Nucleus Impactor (GNI)—A System for the Impaction and Automated Optical Sizing of Giant Aerosol Particles with Emphasis on Sea Salt. Part I: Basic Instrument and Algorithms". Journal of Atmospheric and Oceanic Technology 37, n.º 9 (1 de septiembre de 2020): 1551–69. http://dx.doi.org/10.1175/jtech-d-19-0109.1.
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AbstractSize distributions of giant aerosol particles (dry radius larger than 0.5 μm, sometimes referred to as coarse-mode aerosol particles) are not well characterized in the atmosphere. Measurements are problematic for these particles because they (i) occur in low concentrations, (ii) have difficulty in passing through air inlets, (iii) may be dry or deliquesced particles, and (iv) if sampled by impaction, typically require labor-intensive methods. In this study, a simple, high-volume impaction system called the Giant Nucleus Impactor (GNI), based on free-stream exposure of polycarbonate slides from aircraft, is described along with an automated optical microscope–based system for analysis of the impacted particles. The impaction slides are analyzed in a humidity-controlled chamber (typically 90% relative humidity) that ensures deliquescence of soluble (typically sea salt) particles. A computer-controlled optical microscope with two digital cameras is used to acquire and analyze images of the aerosol particles. At relative humidities above deliquescence (74% RH for sea salt), such particles will form near-spherical cap solution drops on the polycarbonate slides. The sea-salt mass in each giant aerosol particle is then calculated using simple geometry and published water activity measurements. The system has a sample volume of about 10 L s−1 at aircraft speeds of 105 m s−1. For salt particles, the measurement range is from about 0.7 μm dry radius to at least 16 μm dry radius, with a size-bin resolution of 0.2 μm dry radius. The sizing accuracy was tested using polystyrene latex (PSL) beads of known size.
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Ghasemi, Ali y Ali Elham. "Multi-objective topology optimization of pin-fin heat exchangers using spectral and finite-element methods". Structural and Multidisciplinary Optimization, 3 de julio de 2021. http://dx.doi.org/10.1007/s00158-021-02964-6.
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AbstractForced convective pin-fin heat exchangers, due to the high wet surface area per volume and the hindered thermal boundary layers, feature low thermal resistances. However, the considerable coolant pressure drop, particularly for densely packed fin arrays, imposes operational costs for pumping power supply. This paper develops a multi-objective topology optimization approach to optimize sink geometries in order to minimize thermal resistance and pressure loss, concurrently. In accordance to the pin-fin geometrical characteristics, a dedicated pseudo-3D conjugate heat transfer model is utilized, by assuming periodic flow and fin design pattern, to reasonably reduce the high cost of full-3D model optimization. For the solution of flow part, a pseudo-spectral scheme is used, which is intrinsically periodic and features a high spectral accuracy, and the finite element method for the non-periodic conjugate heat transfer model. Exact partial derivatives of the discrete solutions are obtained analytically by hand-differentiation. This task is rather convenient for the flow part, due to the simplicity of the pseudo-spectral implementation; however, the MATLAB symbolic toolbox is selectively utilized for the finite element code to ensure an error-free implementation. Finally, the sensitivities are computed directly or via a discrete adjoint method, for the flow and heat models, respectively. To examine the present approach, two approaches are used for optimization of a practical cooling task: constrained and unconstrained multi-objective formulations, where in all cases more emphasis is placed on thermal resistance minimization. A series of optimized heat sink geometries via constrained or unconstrained multi-objective optimizations are obtained to examine practical utility of the present approach. The optimized topologies demonstrated superior cooling performances at lower costs of pressure losses compared to conventional (circular) in-line and staggered fins, and confirmed the supremacy of topology over pure sizing optimization.
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Wunderlich, T. F., S. Dähne, L. Reimer y A. Schuster. "Global aero-structural design optimization of composite wings with active manoeuvre load alleviation". CEAS Aeronautical Journal, 25 de mayo de 2022. http://dx.doi.org/10.1007/s13272-022-00585-3.
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AbstractIn the scope of the DLR project VicToria (Virtual Aircraft Technology Integration Platform), an integrated process for aero-structural wing optimization based on high fidelity simulation methods is continuously developed and applied. Based upon a parametric geometry, flight performance under transonic flight conditions and manoeuvre loads are computed by solving the Reynolds-averaged Navier–Stokes equations. Structural mass and elastic characteristics of the wing are determined from structural sizing of the composite wing box for essential manoeuvre load cases using computational structural mechanics. Static aeroelastic effects are considered in all flight conditions and active manoeuvre load alleviation is integrated in the process. Global aero-structural wing optimizations are successfully performed for wings with and without active manoeuvre load alleviation. The active manoeuvre load alleviation is introduced with a simplified modelling of control surface deflections using a mesh deformation technique. The minimization of the fuel consumption for three typical flight missions represents the objective function. Wing optimizations are performed for variable and constant wing planform parameters as well as for wings with conventional composite wing box structure and for more flexible wings. The latter is accomplished by introducing modifications of the structural concept and the strain allowable. A significant mass reduction of the optimized wing box is obtained for wings with active manoeuvre load alleviation, resulting in a drop in fuel consumption of about 3%. For wing optimizations with the more flexible wing concept, the active manoeuvre load alleviation shows an additional reduction of the fuel consumption in the order of 2%. The wings with active manoeuvre load alleviation results in optimized wing geometries with increased aspect ratio and reduced taper ratio.
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Haworth, Lauren, Karen May, Jessie Janssen, James Selfe y Ambreen Chohan. "Does an alternative breast support garment provide symptomatic relief for larger breasted women with chronic non-specific back pain?" Prosthetics & Orthotics International, 16 de octubre de 2023. http://dx.doi.org/10.1097/pxr.0000000000000277.
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Background: Nonsurgical guidelines recommend implementing a correctly fitted bra when managing back pain among larger breasted women. Achieving this is challenging with current bra solutions, sizing principles, and fitting approaches. Persistent wearing of an ill-fitting bra can cause negative health implications, including non-specific back pain. Objectives: This study investigated immediate and short-term biomechanical and pain responses to changing breast support garment among larger breasted women with non-specific back pain. Methods: Participants (n = 24) performed a standing task, drop jumps, and seated typing tasks while bra and spinal kinematic data were recorded. Five breast support conditions were assessed: participants’ usual bra (control), a professionally fitted bra in the immediate term (standard) and after 4 weeks wear (standard28), and a bra with an alternative design, measurement, and fitting approach in both the immediate term (alternative) and after 4 weeks wear (alternative28). A bra fit assessment and clinical pain/disability questionnaires were included. Results: All participants failed the bra fit assessment in the control bra, compared with 87.5% (n = 21) in the standard and 4.2% (n = 1) in the alternative bras. The standard28 and alternative28 bras provided symptomatic relief, with the alternative28 bra improving a greater number of outcome measures. Reduced nipple-sternal-notch distance was observed only in the alternative28 bra condition. Conclusions: Symptomatic relief may be associated with the resting position of the breast tissue on the anterior chest wall. The alternative bra may provide potential clinical benefit if implemented as part of a nonsurgical or conservative pain management strategy. Alternative breast support garments should be considered to provide solutions to the problems associated with traditional bras.
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Alessio-Mazzola, Mattia, Pietro Colombo, Niccolo’ Barducci, Elena Ghezzi, Luigi Zagra, Patrizio Caldora, Marco Ometti, Giacomo Placella y Vincenzo Salini. "Direct anterior approach with conventional instruments versus robotic posterolateral approach in elective total hip replacement for primary osteoarthritis: a case–control study". Journal of Orthopaedics and Traumatology 25, n.º 1 (21 de febrero de 2024). http://dx.doi.org/10.1186/s10195-024-00753-7.
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Abstract Background The purpose of this study is to compare peri-operative and short-term outcomes in patients who underwent elective total hip replacement (THA) for primary osteoarthritis (OA) with direct anterior approach (DAA) versus a pair-matched cohort of patients who underwent robotic-assisted THA with posterolateral approach. Materials and methods Data from consecutive patients who underwent elective hip replacement from 2021 to 2023 for primary OA were retrospectively retrieved and divided into two groups: the DAA group, who underwent THA with the DAA approach using conventional instruments, and the robotic posterolateral (R-PL group), who underwent robot arm-assisted THA with the posterolateral approach. Comparative assessed outcomes were: operative time, radiographical implant positioning, intake of rescue analgesics, blood loss, transfusion rate, leg length discrepancy and functional outcomes (Harris hip score and forgotten joint score). Results A total of 100 pair-matched patients were retrieved with a mean age of 66.7 ± 10.7 (range: 32–85) years and a mean follow-up of 12.8 ± 3.6 (range: 7–24) months. No differences in patients’ characteristics were detected. Patients in the R-PL group required less rescue tramadol (p > 0.001), ketorolac (p = 0.028) and acetaminophen (p < 0.001). There was no significant difference in the operative time between (MD = 5.0 min; p = 0.071). Patients in the DAA group had significantly lower Hb levels at day 1 (p = 0.002) without significant differences in transfusion rate (p = 0.283). Patients in the R-PL group had shorter length of stay (LOS) with a mean difference of 1.8 days [p < 0.001; 95% confidence interval (CI) 1.4–2.3]. No difference in clinical outcomes was found [leg length discrepancy (LLD), p = 0.572; HHS, p = 0.558; forgotten joint score (FJS), p = 0.629]. No radiographical differences were measured in cup inclination (MD = 2.0°, p = 0.069), malpositioning [odd ratio (OR) = 0.2; p = 0.141], stem alignment (OR = 0.3; p = 0.485) and stem sizing (OR = 1.5; p = 1.000). There was no difference in complication rate except for lateral femoral cutaneous nerve damage, which was higher in DAA group (p < 0.001). Conclusions R-PL and DAA THA had comparable short-term clinical and radiological outcomes along with similar complication rates. The R-PL group showed significantly lower Hb drop, rescue analgesic consumption and shorter LOS. This is a preliminary study and no strong recommendation can be provided. Further prospective randomized trials are requested to further investigate the cost-effectiveness of robotic surgery in THA. Level of evidence Level IV, case–control study.
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"DESIGN, DEVELOPMENT & ANALYSIS OF AIRCRAFT DROOP NOSE RIBS BY USING OPTIMIZATION TECHNIQUE". International Journal of Engineering Sciences & Research Technology 10, n.º 5 (2021): 32–46. http://dx.doi.org/10.29121/ijesrt.v10.i5.2021.4.
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This master thesis work presents the development of a parameterized automated generic model for the structural design of an aircraft wing. Furthermore, in order to perform finite element analysis on the aircraft wing geometry, the process of finite element mesh generation is automated. The generic model that is developed in this regard is able to automate the process of creation and modification of the aircraft wing geometry based on a series of parameters which define the geometrical characteristics of wing panels, wing spars and wing ribs. Two different approaches are used for the creation of the generic model of an aircraft wing which are “Knowledge Pattern” and “Power Copy with Visual Basic Scripting” using the CATIA V5 Software. A performance comparison of the generic wing model based on these two approaches is also performed. In the early stages of the aircraft design process, an estimate of the structural characteristic of the aircraft wing is desirable for which a surface structural analysis (using 2D mesh elements) is more suitable. In this regard, the process of finite element mesh generation for the generic wing model is automated. Furthermore, the finite element mesh is updated based on any changes in geometry and the shape of the wing panels, wing spars or wing ribs, and ensure that all the mesh elements are always properly connected at the nodes. The automated FE mesh generated can be used for performing the structural analysis on an aircraft wing. Topology optimization has for a considerable time been applied successfully in the automotive industry, but still has not become a mainstream technology for the design of aircraft components.. Also, aircraft components are often stability designs and the compliance based topology optimization method still lacks the ability to deal with any buckling criteria. The present paper considers the use of the compliance formulated topology optimization method and detailed sizing/shape optimization methods to the design of aircraft components but also discusses the difficulties in obtaining correct loading and boundary conditions for finite element based analysis/optimization of components that are integral parts of a larger structure.