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Artykuły w czasopismach na temat "Hybrid absorbing technique"
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Muratov, D. G., L. V. Kozhitov, A. V. Popkova, E. Yu Korovin, E. V. Yakushko i M. R. Bakirov. "Study of the radar absorption of metal-carbon nanocomposites (review)". Industrial laboratory. Diagnostics of materials 89, nr 1 (21.01.2023): 35–45. http://dx.doi.org/10.26896/1028-6861-2023-89-1-35-45.
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Development of the technology for the synthesis of magnetic nanoparticles of metals and alloys has opened up the possibility of their use in the field of radar-absorbing materials (RAM). The results of studying the properties of nanocomposites, method for the synthesis of metal-carbon nanocomposites by pyrolysis using infrared heating are reviewed. The magnetic, electromagnetic, and radar-absorbing properties of the obtained nanocomposites depending on the synthesis temperature and metal concentration were studied. It is shown that the chosen metals, alloys (FeCo) and carbon material are effective for isolating magnetic nanoparticles when developing hybrid radar-absorbing composites. Moreover, methods for controlling the radar-absorbing properties of hybrid composites and the prospects for improving the impedance matching are considered. An analysis of the efficiency of absorption of electromagnetic radiation by FeCo/C nanocomposites synthesized by different methods is presented. The possibility of controlling the morphology and properties of metal-carbon nanocomposites using certain approaches to synthesis, varying the compositions of precursors, and the orientation of FeCo nanoparticles synthesized in the form of flakes in the composite has been revealed. The results of the study can be used to improve the technique of using FeCo/C nanocomposites obtained by pyrolysis of organometallic precursors based on polyacrylonitrile in the field of radar-absorbing materials.
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Salisu, Bashir. "CHARACTERIZATION OF HYBRID-FORMAMIDINIUM BISMUTH BROMIDE PEROVSKITE MATERIAL (FABi2Br9) SYNTHESIZED VIA GROWTH ASSISTED TECHNIQUE FOR SOLAR CELLS APPLICATION". FUDMA JOURNAL OF SCIENCES 5, nr 3 (2.11.2021): 169–76. http://dx.doi.org/10.33003/fjs-2021-0503-694.
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ABSTRACT
In the last decade, organic-inorganic perovskite solar cells (PSCs) have had tremendous success, raising their power conversion efficiency from 3.8% in 2009(T, A, K, & Y, 2009) to >25.6% (Li et al., 2021). Perovskite material is newly emergent, third-generation solar cells, it generally refers to any composite that has structure like that of calcium titanium oxide (CaTiO2). It has a general formula ABX3, where A refers to an organic compound, B is an inorganic and X represents the halides. In this research, a Hybrid-Formamidinium Bismuth Bromide Perovskite solar cell (FABi2Br9) was synthesized via a novel crystal growth process and subjected to characterization for determining its optoelectronic properties for solar cells application. The x-ray diffraction (XDR) results revealed the crystal hexagonal structure of FABi2Br9, the crystal sizes were obtained and it gives an excellent size (74nm) for light absorption material. The bandgap was determined using ultraviolet-visible spectroscopy (U.V vis) which was found to be 1.80eV which is within the required range for an absorbing layer in a solar cell architecture. Nuclear magnetic resonance (NMR) and was used to identify the organic content purity of the composite. In conclusion, FABi2Br9 was found to be pure with excellent optoelectronics properties that can readily be used as an absorbent layer in perovskite solar cells architecture
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Cantrell, Will, i George E. Ewing. "Attenuated (but Not Total) Internal Reflection FT-IR Spectroscopy of Thin Films". Applied Spectroscopy 56, nr 5 (maj 2002): 665–69. http://dx.doi.org/10.1366/0003702021955240.
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We present a spectroscopic technique that is a hybrid between reflection-absorption and attenuated total reflection (ATR) spectroscopy. The method, which we call attenuated internal reflection (AIR), is suitable for the investigation of thin film liquids on non-or weakly absorbing substrates. In AIR the interrogating infrared beam is not exposed to vapor that may be associated with the film, but unlike ATR there are few geometric constraints on the substrate. We show the theoretical basis for the method and results from experiments demonstrating its use.
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Mohamad, Barhm, Jalics Karoly, Andrei Zelentsov i Salah Amroune. "A hybrid method technique for design and optimization of Formula race car exhaust muffler". International Review of Applied Sciences and Engineering 11, nr 2 (sierpień 2020): 174–80. http://dx.doi.org/10.1556/1848.2020.20048.
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AbstractIn this work a multilevel Computational Fluid Dynamics (CFD) analysis has been applied for the design of a Formula race car exhaust muffler with improved characteristics of sound pressure level (SPL) and fluid dynamic response. The approaches developed and applied for the optimization process range from the 1D to fully 3D CFD simulation, exploring hybrid approaches based on the integration of a 1D model with 3D tools. Modern mufflers typically have a complex system of chambers and flow paths. There are a variety of sound damping and absorbing mechanisms working to quiet the sound flowing through a muffler and piping system. Two calculation methods were selected for this study. The muffler has a complex inner structure containing perforated pipe and fiber material. Computer-aided design (CAD) file of the muffler was established for developing Finite Element Analysis (FEA) model in AVL BOOST v2017 and another commercial advanced design software (SolidWorks 2017). FEA model was made to monitor the flow properties, pressure and velocity. After the model was verified, sensitivity studies of design parameters were performed to optimize the SPL of the muffler. The software analysis results are included in the paper. Recommendations are made for obtaining smoother SPL curves for various measurement methods.
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Tao, Chenglin, Zhao Wang, Zeliang Liu, Yuan Wang, Xin Zhou, Xi Liang i Huijian Li. "Crashworthiness of Additively Manufactured Lattice Reinforced Thin-Walled Tube Hybrid Structures". Aerospace 10, nr 6 (1.06.2023): 524. http://dx.doi.org/10.3390/aerospace10060524.
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In this paper, a new hybrid structure of body-centered cubic lattice-filled thin-walled tube is designed, and the hybrid structure specimens of one-piece printing and split-printing are prepared by laser melting technique. The deformation mode and energy absorption characteristics of the new hybrid structure are investigated by experiments and numerical simulations. Under axial compression, the one-piece printed hybrid structure forms more wrinkles with smaller wavelengths, and the specific energy absorption increases by 12.14% compared with the split-printed structure; under transverse compression, the one-piece printed structure does not show the separation of the thin-walled tube from the lattice, and the specific energy absorption increases by 134.83% compared with the split-printed structure. It is worth noting that the designed hybrid structure has a 112.60% (580.15%) increase in specific energy absorption under axial compression (under transverse compression) compared to the empty tube. The effects of wall thickness, lattice density, and loading rate on the crashworthiness of the hybrid structure were investigated using a validated finite element model. This paper provides a new idea for the preparation of lightweight and high-strength energy-absorbing structures.
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Huang, Shaowu, Gary Charles, Kai Xiao i Beomtaek Lee. "REDUCTION OF PCB PDN IMPEDANCE AND RADIATED EMISSIONS USING A HYBRID TECHNIQUE WITH ABSORBING MATERIALS AND DECOUPLING CAPACITORS". Progress In Electromagnetics Research B 77 (2017): 137–54. http://dx.doi.org/10.2528/pierb17041605.
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Dolci, Daiane Iglesia, Felipe A. G. Silva, Pedro S. Peixoto i Ernani V. Volpe. "Effectiveness and computational efficiency of absorbing boundary conditions for full-waveform inversion". Geoscientific Model Development 15, nr 14 (27.07.2022): 5857–81. http://dx.doi.org/10.5194/gmd-15-5857-2022.
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Abstract. Full-waveform inversion (FWI) is a high-resolution numerical technique for seismic waves used to estimate the physical characteristics of a subsurface region. The continuous problem involves solving an inverse problem on an infinite domain, which is impractical from a computational perspective. In limited area models, absorbing boundary conditions (ABCs) are usually imposed to avoid wave reflections. Several relevant ABCs have been proposed, with extensive literature on their effectiveness on the direct wave problem. Here, we investigate and compare the theoretical and computational characteristics of several ABCs in the full inverse problem. After a brief review of the most widely used ABCs, we derive their formulations in their respective adjoint problems. The different ABCs are implemented in a highly optimized domain-specific language (DSL) computational framework, Devito, which is primarily used for seismic modelling problems. We evaluate the effectiveness, computational efficiency, and memory requirements of the ABC methods, considering from simple models to realistic ones. Our findings reveal that, even though the popular perfectly matching layers (PMLs) are effective at avoiding wave reflections at the boundaries, they can be computationally more demanding than less used hybrid ABCs. We show here that a proposed hybrid ABC formulation, with nested Higdon's boundary conditions, is the most cost-effective method among the methods considered here, for being as effective as or more effective than PML and other schemes but also for being computationally more efficient.
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Xu, Run-Wen, i Li-Xin Guo. "Application of Hybrid Finite Element-Boundary Integral Algorithm for Solving Electromagnetic Scattering from Multiple Objects over Rough Sea Surface". International Journal of Antennas and Propagation 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/301934.
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A hybrid algorithm of the finite element method (FEM) is presented to solve two-dimensional (2D) scattering from multiple dielectric objects above the rough sea surface. Compared with traditional FEM based on approximate absorbing boundaries, FEM based on the boundary integral method (BIM) can reduce the calculational region and solution time of the scattering problem. In the hybrid method, the whole computational region is divided into the sea surface and multiple isolate interior regions for the dielectric objects. FEM is only used to simulate the scattering from multiple interior regions enclosing the objects, whereas the large sea is considered exactly by BIM. The coupled interaction among the isolate interior regions and the sea can be taken into account by BIM. The hybrid technique presented here is efficient and versatile for addressing scattering from multiple arbitrary targets above rough sea surfaces. Scattering properties of multiple dielectric objects above the sea surface under different conditions are discussed in detail.
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Acanfora, Valerio, Ferdinando Baldieri, Antonio Garofano, Francesco Fittipaldi i Aniello Riccio. "On the Crashworthiness Behaviour of Innovative Sandwich Shock Absorbers". Polymers 14, nr 19 (4.10.2022): 4163. http://dx.doi.org/10.3390/polym14194163.
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Increasing the impact resistance properties of any transport vehicle is a real engineering challenge. This challenge is addressed in this paper by proposing a high-performing structural solution. Hence, the performance, in terms of improvement of the energy absorbing characteristics and the reduction of the peak accelerations, of highly efficient shock absorbers integrated in key locations of a minibus chassis have been assessed by means of numerical crash simulations. The high efficiency of the proposed damping system has been achieved by improving the current design and manufacturing process of the state-of-the-art shock absorbers. Indeed, the proposed passive safety system is composed of additive manufactured, hybrid polymer/composite (Polypropylene/Composite Fibres Reinforced Polymers—PP/CFRP) shock absorbers. The resulting hybrid component combines the high stiffness-to-mass and strength-to-mass ratios characteristic of the composites with the capability of the PP to dissipate energy by plastic deformation. Moreover, thanks to the Additive Manufacturing (AM) technique, low-mass and low-volume highly-efficient shock-absorbing sandwich structures can be designed and manufactured. The use of high-efficiency additively manufactured sandwich shock absorbers has been demonstrated as an effective way to improve the passive safety of passengers, achieving a reduction in the peak of the reaction force and energy absorbed in the safety cage of the chassis’ structure, respectively, up to up to 30 kN and 25%.
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Sakthivel, Santhanam, Selvaraj Senthil Kumar, Eshetu Solomon, Gedamnesh Getahun, Yohaness Admassu, Meseret Bogale, Mekdes Gedilu, Alemu Aduna i Fasika Abedom. "Sound absorbing and insulating properties of natural fiber hybrid composites using sugarcane bagasse and bamboo charcoal". Journal of Engineered Fibers and Fabrics 16 (styczeń 2021): 155892502110448. http://dx.doi.org/10.1177/15589250211044818.
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This research paper reports a study on thermal and sound insulation samples developed from sugarcane bagasse and bamboo charcoal for automotive industry applications. The sugarcane bagasse and bamboo charcoal fiber is a potential source of raw material that can be considered for thermal and sound insulation applications. Natural fibers are commonly used in diverse applications and one of the most important applications is sound absorption. Natural fiber hybrid composite currently is in greater demand in industries because of their advantages such as low cost, biodegradability, acceptable physical properties, and so on. Eco-friendly sound-absorbing composite materials have been developed using bamboo charcoal and sugarcane bagasse fibers. From these fibers five types of natural fiber green composite were developed using the compression bonding technique. The natural composite noise control performance contributes to its wider adoption as sound absorbers. The sound absorption coefficient was measured according to ASTM E 1050 by the Impedance tube method. The physical properties of natural fiber composites such as thickness, density, porosity, air permeability, and thermal conductivity were analyzed for all samples in accordance with ASTM Standard. The result exposed that natural fiber green composite were absorbing the sound resistance of more than 70% and the natural fibers composites provide the best acoustic absorption properties, these composite materials have adequate moisture resistance at high humidity conditions without affecting the insulation and acoustic properties.
Streszczenia konferencji na temat "Hybrid absorbing technique"
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Kimbro, Evan, i Ajit D. Kelkar. "Development of Energy Absorbing Laminated Fiberglass Composites Using Electrospun Glass Nanofibers". W ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64746.
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Failure due to delamination of composite laminates via low velocity impact damages is critical because of the subsurface nature of delamination. Traditional methods such as stitching and Z-pinning, while improving interlaminar properties in woven composites, lead to a reduction of the in-plane properties. Electrospun non-woven sheets of nanofibrous mat applied at interfacial regions offer an option to traditional treatments. The objective of the present study is to observe the energy absorption during the event of an impact upon a composite laminate. The use of Tetra Ethyl Orthosilicate (TEOS) chemically engineered glass nanofibers manufactured using electrospinning technique in woven glass fiber resin pre-impregnated composite laminates were investigated for their potential to improve the interlaminar properties. Electrospun glass nanofibers pre-impregnated woven mats were manufactured using a vacuum bag and cured in a computer controlled convection oven. The interlaminar properties of the nano engineered hybrid composites were obtained using low velocity impact tests and are compared with those without the presence of electrospun nanofiber layers, to study their influence. Impacted specimens were examined using C-scan analysis to detect impact damage dimensions. It was observed when electrospinning nanofibers were added to lamina interfaces, the electrospun fiber embedded coupons had larger impact damage area compared to the coupons without electrospun fiber layers.
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Guo, Lianshui, Charles L. Penninger, John E. Renaud i Andre´s Tovar. "Strain-Based Topology Optimization for Crashworthiness Using Hybrid Cellular Automata". W ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-86348.
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Structural design for crashworthiness is a challenging area of research due to large plastic deformations and complex interactions among diverse components of the vehicle. Previous research in this field primarily focused on energy absorbing structures that utilize a desired amount of material. These structures have been shown to absorb a large amount of the kinetic energy generated during the crash event; however, the large plastic strains experienced can lead to failure. This research introduces a new strain-based topology optimization algorithm for crash-worthy structures undergoing large deformations. This technique makes use of the hybrid cellular automaton framework combining transient, non-linear finite-element analysis and local control rules acting on cells. The set of all cells defines the design domain. In the proposed algorithm, the design domain is dynamically divided into two sub-domains for different objectives, i.e., high strain sub-domain (HSSD) and low strain sub-domain (LSSD). The distribution of these sub-domains is determined by a plastic strain limit value. During the design process, the material is distributed within the LSSD following a fully-internal-energy-distribution principle. To accomplish that, each cell in the LSSD is driven to a prescribed target or set point value by modifying its stiffness. In the HSSD, the material is distributed to satisfy a failure criterion given by a maximum strain value. Results show that the new formulation and algorithm are suitable for practical applications. The case studies demonstrate the potential significance of the new capability developed for a wide range of engineering design problems.
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Elmasry, Ahmed, Wiyao Azoti i Ahmed Elmarakbi. "Finite Element-Incorporated Multiscale Micromechanics Modelling of Vehicle Crashworthiness for 3-Phases Hybrid Fibres Reinforced Graphene Nano-Composite Materials". W ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-95091.
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Abstract Crashworthiness focuses on the safety and protection of occupants. In addition, not only do energy absorbing members have to absorb sufficient collision energy, but the vehicle structure must be lightweight to improve power consumption. Nevertheless, estimating vehicle crashworthiness is experimentally expensive and time-consuming. Explicit nonlinear finite element analysis (FEA) is probably the most commonly used modelling technique to evaluate vehicle behaviour during a crash. However, commercial FE software still lacks efficient explicit modelling of lightweight graphene-based nano-composites. This work develops a simple approach to studying 3-phases hybrid fibres/graphene nanoplatelets-reinforced polymer matrix composites through multiscale modelling. Thermo-elasto-plastic response of composites is considered. The heterogeneous material problem is resolved through a kinematic integral equation. A linear spring model LSM is adopted to account for the interfacial behaviour in a modified Mori-Tanaka scheme The non-linear response is established in the framework of the J2 plasticity flow rule coupled with the “Lemaitre-Chaboche” ductile damage. The considered material is short glass -fibres/graphene nanoplatelet/Polyamide-Nylon 6 composite. The model is implemented as a UMAT within LS-DYNA® software for automotive crashworthiness applications. The results highlight the crash performance’s impact, incorporating the influence of the interfacial behaviour and material damage on the peak crash force and specific energy absorption SEA.
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Serres, Jennifer L., Dan V. Jones, Rabih E. Tannous, Nathan Dau i Cynthia A. Bir. "Evaluation of Lower Limb Injury Mitigation Techniques for High Velocity Impacts With the Mil-LX". W ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53269.
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Improvised Explosive Devices (IED) and landmines present a significant threat to mounted troops currently serving in Iraq and Afghanistan. As a result of these threats, a substantial number of lower limb injuries are sustained by service members. Due to this reality, a critical factor in military vehicle design is the mitigation of lower limb trauma. Past studies have shown that the standard Hybrid III and THOR-LX are not biofidelic in military axial loading conditions (up to 12 m/s). Both of these surrogates over predict axial forces compared to Post Mortem Human Specimens (PMHS) [1]. As a result, a new surrogate was developed, Mil-LX (Military Lower Extremity), that matches the PMHS response for axial loading of the lower leg up to 12 m/s [2,3]. While injury mitigation techniques, such as energy absorbing mats, foot rests, and isolation floors, have been effective in reducing lower extremity injuries in live fire test events, there are several variants of each of these methods. Additionally, it has also been suggested that the positioning of the lower limbs may affect the load sustained by these extremities [4].
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Derickson, D. J., R. J. Helkey, A. Mar, R. L. Thornton i J. E. Bowers. "Benefits of intrawaveguide saturable absorbers in external cavity mode-locked semiconductor lasers". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.mg5.
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Actively mode-locked semiconductor lasers need high quality antireflection coatings to avoid multiple pulse formation and mode-locking in clusters. The addition of an intrawaveguide saturable absorber eliminates these problems by absorbing the reflected pulses from the antireflection coating. Saturable absorption also causes pulse shortening and introduces self-phase modulation opposite in sign to that of saturable gain. Two section lasers with four GaAs quantum well active regions were compared using active and hybrid mode-locking techniques. The saturable absorber is formed by reverse biasing an 80-μm end segment and high reflection coating the facet. The opposite facet has a 10-3 antireflection coating for a 200-ps roundtrip time external cavity. Active mode-locking produced 9.5-ps pulses with a 400-GHz spectral width at 1-mW average power. Mode-locking was in clusters as evidenced by 8-dB nulls in the spectrum due to laser diode Fabry-Perot modes. The addition of the saturable absorber reduced the pulse width to 2.5 ps with an 800-GHz spectral width. The spectral ripple was reduced to 0.5 dB and the time–bandwidth product improved from 3.8 to 2.0. The impulse response of the saturable absorber photocurrent was measured as 45 ps showing that a p-i-n reversed biased absorber can recover quickly without the need for proton bombardment or other means to shorten electronic lifetime.
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Kitzmiller, Kyle, i Fletcher Miller. "Thermodynamic Cycles for a Small Particle Heat Exchange Receiver Used in Concentrating Solar Power Plants". W ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90229.
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Gas-cooled solar receivers for concentrating solar power plants are capable of providing high temperature, pressurized gas for electrical power generation via a Brayton cycle. This can be accomplished by expanding hot, pressurized gas directly through a turbine, or through using a heat exchanger to indirectly heat pressurized air. Gas-cooled receivers can be divided into two basic technologies. In tube based solar receivers, thermal energy is transferred to air through convection with the heated tube wall. This limits receiver efficiency since the tube wall needs to be substantially hotter than the gas inside due to the relatively poor gas heat transfer coefficient. In volumetric receivers, solar energy is absorbed within a volume, rather than on a surface. The absorption volume can be filled with ceramic foam, wires, or particles to act as the absorbing medium. In a small particle heat exchange receiver, for example, sub-micron sized particles absorb solar radiation, and transfer this energy as heat to a surrounding fluid. This effectively eliminates any thermal resistance, allowing for higher receiver efficiencies. However, mechanical considerations limit the size of volumetric, pressurized gas-cooled receivers. In order to solve this problem, several thermodynamic cycles have been investigated, each of which is motivated by key physical considerations in volumetric receivers. The cyclic efficiencies are determined by a new MATLAB code based on previous Brayton cycle modeling conducted by Sandia National Laboratories. The modeling accounts for pressure drops and temperature losses in various components, and parameters such as the turbine inlet temperature and pressure ratio are easily modified to run parametric cases. The performance of a gas-cooled solar receiver is largely a function of its ability to provide process gas at a consistent temperature or pressure, regardless of variations in solar flux, which can vary due to cloud transients or apparent sun motion throughout the day. Consistent output can be ensured by combusting fuel within the cycle, effectively making a solar/fossil fuel hybrid system. Several schemes for hybridization with natural gas are considered here, including externally fired concepts and combined receiver/combustor units. Because the efficiency of hybridized cycles is a function of the solar thermal input, the part load behavior of the recuperated cycle is examined in depth. Finally, a brief report of economic costs inherent to solar powered gas turbine engines is given. Possibilities for the future of solar power gas turbine power plants are discussed, with key issues regarding thermal storage techniques.