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Design and Optimization of a Solar Power Conversion System for Space Applications
摘要： This manuscript details a design method for a 500kW solar power based microgrid system for space applications. The design method utilizes multi-objective optimization with the Genetic Algorithm considering four parameters that characterize solar power based microgrids (battery voltage, PV maximum power, PV maximum power point voltage, and number of panels per string). The final optimization metric is the ratio of daily average deliverable power to total system mass (W/kg) metric. The microgrid system is composed of a number of modular DC-DC micro-converters, of which four topologies (buck, boost, buck-boost and non-inverting buck-boost) are evaluated and compared. The non-inverting buck-boost converter is determined to be the best candidate, and the optimal system characteristics are provided and analyzed. The final system design achieves a specific power of 35.56W/kg, with optimized result of 743.7V battery voltage, 439.5W PV maximum power, 182.7V PV maximum voltage, and three panels per string. Based on the optimizations results, a prototype is designed, tested, and analyzed in terms of efficiency and low temperature reliability. The converter achieved a peak efficiency of 98.4%, a power density of 3.54W/cm3, a specific power of 3.76W/g, and operated for over 267 hours of 11-minute low temperature cycles from 0oC to -140oC.
关键词： low temperature testing,photovoltaic systems,wide band gap semiconductors,maximum power point trackers,design optimization,non-inverting buck-boost,space exploration,system-level design,DC-DC power converters,microgrids
更新于2025-09-23 15:22:29
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Enantioselective Visible Light-mediated Formation of 3-Cyclopropylquinolones via Triplet-sensitized Deracemization
摘要： 3-Allyl-substituted quinolones undergo a triplet-sensitized di-π-methane rearrangement to the corresponding 3-cyclopropylquinolones upon irradiation with visible light (λ = 420 nm). A chiral hydrogen bonding sensitizer (10 mol%) was shown to promote the reaction enantioselectively (88-96% yield, 32-55% ee). Surprisingly, it was found that the enantiodifferentiation does not occur at the state of initial product formation but that it is the result of a deracemization event. The individual parameters that control the distribution of enantiomers in the photostationary state have been identified.
关键词： enantioselectivity,small ring systems,photochemistry,hydrogen bonds,sensitizers,chiral resolution
更新于2025-09-23 15:22:29
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Polygamy relation for the Rényi-$$\alpha $$α entanglement of assistance in multi-qubit systems
摘要： We prove a new polygamy relation of multi-party quantum entanglement in terms of Rényi-α entanglement of assistance for (√7?1)/2 ≤ α ≤ (√13?1)/2. This class of polygamy inequality reduces to the polygamy inequality based on entanglement of assistance since Rényi-α entanglement is a generalization of entanglement of formation.
关键词： Rényi-α entanglement of assistance,Multi-qubit systems,Polygamy relation
更新于2025-09-23 15:22:29
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Automated daylight-linked control systems performance with illuminance sensors for side-lit offices in the Mediterranean area
摘要： Daylight-linked control systems (DLCSs) installation guarantees noticeable benefits, optimizing both energy saving and occupants' visual comfort. These systems performances are influenced by different factors, above all daylight availability. To deepen this issue, daylight illuminance measurements were performed at the work-plane and at the ceiling (corresponding to the position of a typical closed-loop photosensor) in a side-lit office during summer and winter. The office was equipped with two windows: one facing South and the other facing West. For each orientation, starting from measurements, the functioning of different closed-loop DLCSs was modelled. Results underlined that proportional dimming systems guarantee the best performances for each analyzed case, however they demonstrated that, for specific indoor daylight levels and task illuminances, switching systems can be profitable as well. It was underlined that, for specific daylight conditions, integral reset control guarantees performances comparable with those of proportional dimming. However, it was observed that for integral reset and multi-levels stepped systems, the risk that total illuminances (daylight plus electric light) are lower than the prescribed ones is higher than the other analyzed control strategies.
关键词： Daylight illuminance measurements,Mediterranean area daylighting,Automated daylight-linked control systems,Energy savings,Daylight
更新于2025-09-23 15:22:29
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Quantifying soil carbon stocks and humification through spectroscopic methods: A scoping assessment in EMBU-Kenya
摘要： A soil carbon assessment was performed comparing agricultural cropping systems with natural vegetation along a sampling transect spanning different agro-ecologies on the eastern foot slopes of Mount Kenya in Embu county, 125 km from Nairobi, Kenya. The aim was to determine differences in soil carbon stocks and carbon recalcitrance and relate these to soil textural class, altitude, climatic parameters and land use. Soils from main agricultural systems as tea, coffee and maize-based intercropping, as well as from natural vegetation cover were sampled in triplicates, in five layers from 0 to 30 cm in depth and processed for total carbon analysis. The whole soil samples were also analysed using Laser-Induced Fluorescence Spectroscopy (LIFS) to assess carbon humification. Prototype portable equipment intended for future in situ analysis was used in the lab to ascertain the structure of the most recalcitrant and stable carbon present in different agro-ecosystems. In addition, Near Infrared Spectroscopy (NIRS) was tested for the quantitative analysis of soil carbon, showing that it is a reproducible and low-cost method that provided satisfactory results under the processing conditions of the samples. Results showed wide variation in the level and quality of carbon stored in the soils, depending on soil texture, land use, elevation, climate, agricultural practices and land use history. Considering the heterogeneous nature of sampled soils and the performance of NIRS and LIFS, these results can be used as a basis for the development of fully portable systems able to provide rapid, clean and potentially cost-effective relevant information for soil management.
关键词： Agricultural cropping systems,Nitisols,Soil carbon stocks,Carbon humification,Mount Kenya,Andosols,Spectroscopy
更新于2025-09-23 15:22:29
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The GAPS Programme with HARPS-N at TNG
摘要： Context. Statistical studies of exoplanets have shown that giant planets are more commonly hosted by metal-rich dwarf stars than low-metallicity stars, while no such correlation is evident for lower mass planets. The search for giant planets around metal-poor stars and the estimate of their occurrence fp is an important element in providing support to models of planet formation. Aims. We present results from the HARPS-N search for giant planets orbiting metal-poor ([Fe/H] ≤ -0.5 dex) stars in the northern hemisphere, complementing a previous HARPS survey on southern stars in order to update the estimate of fp. Methods. High-precision HARPS-N observations of 42 metal-poor stars were used to search for planetary signals to be fitted using differential evolution Markov chain Monte Carlo single-Keplerian models. We then joined our detections to the results of the previous HARPS survey on 88 metal-poor stars to provide a preliminary estimate of the two-hemisphere fp. Results. We report the detection of two new giant planets around HD 220197 and HD 233832. The first companion has Msin i = 0.20+0.07-0.04 MJup and an orbital period of 1728+162-80 days, and for the second companion, we find two solutions of equal statistical weight with periods of 2058+47-40 and 4047+91-117 days and minimum masses of 1.78+0.08-0.06 and 2.72+0.23-0.23 MJup, respectively. Joining our two detections with the three from the southern survey, we obtain a preliminary and conservative estimate of the global frequency of fp = 3.84+2.45-1.06% for giant planets around metal-poor stars. Conclusions. The two new giant planets orbit dwarf stars at the metal-rich end of the HARPS-N metal-poor sample. This corroborates previous results that suggested that giant planet frequency is still a rising function of the host star [Fe/H]. We also note that all detections in the overall sample are giant long-period planets.
关键词： stars: individual: HD 220197,techniques: radial velocities,stars: abundances,stars: individual: HD 233832,methods: data analysis,planetary systems
更新于2025-09-23 15:22:29
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Efficient method to calculate the optical quantities of multi-layer systems with randomly rough boundaries using the Rayleigh-Rice theory
摘要： An efficient and numerically stable method for calculating the optical quantities of multi-layer systems with slightly rough boundaries using the second order Rayleigh–Rice theory is developed. It is assumed that the mean planes of the boundaries are parallel and all the media forming the system are nonmagnetic, isotropic and homogeneous. The perturbation series is formulated using the four-dimensional formalism inspired by the Yeh matrix formalism, but the final result is written using the two-dimensional formalism which is more efficient for the numerical calculations. The final formulae, which are expressed using an arbitrary power spectral density function, include the mixing between the p and s polarizations occurring for anisotropic roughness. Although in the general case the calculation of optical quantities requires evaluation of double integrals, it is shown that for the power spectral density function given by the isotropic Gaussian function some integrals can be calculated analytically and only single integrals have to be evaluated numerically. The random roughness of boundaries is a defect that occurs frequently in practice, and it must be taken into account in the optical characterization and synthesis of thin film systems exhibiting this defect. The presented method is suitable for these purposes, since both of the mentioned applications require methods that are very fast.
关键词： multi-layer systems,optical quantities,Rayleigh–Rice theory,random boundary roughness
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE XXVII International Scientific Conference Electronics (ET) - Sozopol (2018.9.13-2018.9.15)] 2018 IEEE XXVII International Scientific Conference Electronics - ET - Contactless transmission of power and control signals by multiplexing the frequency
摘要： For contactless power transmission systems, the actual scientific topic is the parallel two-way communication between the transmitting and receiving sides through the same power electromagnetic module. This technical solution enables the removal of the additional contactless module for the transmission of information and control signals and respectively, for improvement of the operational and technical characteristics of the contactless transmitters. This paper examines inductive methods that integrate bidirectional data transmission in the power module system for energy transfer. Various methods for the simultaneous transmission of energy and data are analyzed. Main attention is paid to the frequency multiplexing method, with its advantages over other methods.
关键词： Frequency Multiplexing,Information Signals,Data Transfer,Contactless Systems
更新于2025-09-23 15:22:29
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Nature of the excited states of layered systems and molecular excimers: Exciplex states and their dependence on structure
摘要： Weakly bound systems, like noble-gas dimers or two-dimensional layered materials (graphite, hexagonal boron nitride, or transition-metal dichalcogenides), exhibit excited electronic states of a particular nature. These so-called exciplex states combine on-site (or intralayer) and charge-transfer (or interlayer) configurations in a well-balanced way. We show by ab initio many-body perturbation theory that the energy and composition of the exciplex states depend sensitively on the bond length or interlayer distance of the material. When the constituents approach each other, the charge-transfer contribution increases and the excitation is redshifted to lower energy. If the system is excited into the exciplex state, then a covalent-like bond results. In consequence, noble-gas dimers form excimer complexes, while layered materials exhibit interlayer contraction.
关键词： charge-transfer excitations,many-body perturbation theory,interlayer contraction,exciplex states,layered systems
更新于2025-09-23 15:22:29
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Robust 3D object reconstruction based on camera clustering with geodesic distance
摘要： This Letter presents a method that reconstructs 3D object using camera clustering and key camera selection to resolve scalability problem. To perform camera clustering, camera similarity is defined using geodesic distance and overlap constraint between cameras. Key cameras are then selected to reconstruct an object considering overlapping cameras and high curvature regions. As a result, it is achievable to relax increases in the execution time and the accumulated errors due to the scalability problems with a large number of cameras.
关键词： three-dimensional displays,image reconstruction,Clustering methods,Robot vision systems
更新于2025-09-23 15:22:29