Implementation strategies for multiband quantum simulators of real materials

The majority of quantum simulators treat simplified one-band strongly correlated models, whereas multiple bands are needed to describe materials with intermediate correlation. We investigate the sensitivity of multiband quantum simulators to: (1) the form of optical lattices, (2) the interactions between electron analogs. Since the kinetic-energy terms of electron analogs in a quantum simulator and electrons in a solid are identical, by examining both periodic potential and interaction we explore the full problem of many-band quantum simulators within the Born–Oppenheimer approximation. Density functional calculations show that band structure is highly sensitive to the form of optical lattice, and it is necessary to go beyond sinusoidal potentials to ensure that the bands closest to the Fermi surface are similar to those in real materials. Analysis of several electron analog types finds that dressed Rydberg atoms (DRAs) have promising interactions for multiband quantum simulation. DRA properties can be chosen so that interaction matrices approximate those in real systems and decoherence effects are controlled, albeit with parameters at the edge of currently available technology. We conclude that multiband quantum simulators implemented by using the principles established here could provide insight into the complex processes in real materials

The hardware is the software

Human brains and bodies are not hardware running software: the hardware is the software. We reason that because the microscopic physics of artificial-intelligence hardware and of human biological "hardware" is distinct, neuromorphic engineers need to be cautious (and yet also creative) in how we take inspiration from biological intelligence. We should focus primarily on principles and design ideas that respect -- and embrace -- the underlying hardware physics of non-biological intelligent systems, rather than abstracting it away. We see a major role for neuroscience in neuromorphic computing as identifying the physics-agnostic principles of biological intelligence -- that is the principles of biological intelligence that can be gainfully adapted and applied to any physical hardware

A New Approach To Measure Unique Spectral Response Characteristics For Irregularly Shaped Photovoltaic Arrays

Current photovoltaic (PV) panel test methods do not provide efficient and repeatable standardization, which can result in inconsistent results. Test requirements for individual PV cells are promulgated by standard test conditions (STC), but do not directly translate to new array or panel designs, particularly for panels that are irregularly shaped and used for different applications. Optimal angles that yield the most power delivery from the PV device when integrated into a panel are achieved by manipulating the panel’s orientation via single or dual axis tracking (e.g., maximum power point tracking). In applications where PV is intended to be integrated into a flying object, such as an unmanned aerial vehicle (UAV), maximum power point tracking (MPPT) is not an option due to aerodynamic constraints resulting from airfoil and control surface design. In these instances, it is pertinent to develop a system that can consistently measure responses of a PV-embedded airfoil in a controlled environment that is also cost-efficient and readily available for researchers to use. Additionally, the system must also be scalable to meet the needs of larger experimental setups for future UAV development. The intent of this dissertation was to propose a new method for capturing the PV-embedded airfoil performance as it compares to a conventional flat panel in terms of efficiencies. As a result, a user has the ability to analyze the collected experimental data and subsequently develop a performance correction factor that is specific to the airfoil used. Recommendations to further enhance analysis of UAV integrated PV efficiency factors, such as vibration impacts on performance, will also be discussed. From an analysis of experimental data, unmanned aerial systems (UAS) engineers can be able to integrate renewable energy systems more effectively and therefore increase vehicle energy efficiency

Machine learning reveals orbital interaction in crystalline materials

We propose a novel representation of crystalline materials named orbital-field matrix (OFM) based on the distribution of valence shell electrons. We demonstrate that this new representation can be highly useful in mining material data. Our experiment shows that the formation energies of crystalline materials, the atomization energies of molecular materials, and the local magnetic moments of the constituent atoms in transition metal--rare-earth metal bimetal alloys can be predicted with high accuracy using the OFM. Knowledge regarding the role of coordination numbers of transition-metal and rare-earth metal elements in determining the local magnetic moment of transition metal sites can be acquired directly from decision tree regression analyses using the OFM.Comment: 10 page

Handbook of space environmental effects on solar cell power systems

Space environmental effects on solar cell power systems for earth satellite

Solar cell radiation handbook

The handbook to predict the degradation of solar cell electrical performance in any given space radiation environment is presented. Solar cell theory, cell manufacturing and how they are modeled mathematically are described. The interaction of energetic charged particles radiation with solar cells is discussed and the concept of 1 MeV equivalent electron fluence is introduced. The space radiation environment is described and methods of calculating equivalent fluences for the space environment are developed. A computer program was written to perform the equivalent fluence calculations and a FORTRAN listing of the program is included. Data detailing the degradation of solar cell electrical parameters as a function of 1 MeV electron fluence are presented

Design and Validation of an LED-Based Solar Simulator for Solar Cell and Thermal Testing

An LED-based solar simulator has been designed, constructed, and qualified under ASTM standards for use in the Cal Poly Space Environments Laboratory. The availability of this simulator will enhance the capability of undergraduate students to evaluate solar cell and thermal coating performance, and offers further research opportunities. The requirements of ASTM E927-19 for solar simulators intended for photovoltaic cell testing were used primarily, supplemented by information from ASTM E491-73 for solar simulators intended for spacecraft thermal vacuum testing. Three main criteria were identified as design goals - spectral match ratio, spatial non-uniformity, and temporal instability. An electrical design for an LED-based simulator to satisfy these criteria was developed and implemented, making use of existing lab equipment where possible to minimize cost. The resulting simulator meets the desired spatial non-uniformity and temporal instability requirements of ASTM E927-19, but falls short of the spectral match ratio needed. This is shown to be due to a calibration issue that is easily amended via software. The simulator is overall Class UCB under ASTM E927, and Class CCC under ASTM E491. The simulator was used to conduct the same laboratory procedure for solar cell I-V curve testing as performed by undergraduate students, showing excellent promise as a course enhancement

Development of a Nanoelectronic 3-D (NEMO 3-D) Simulator for Multimillion Atom Simulations and Its Application to Alloyed Quantum Dots

Material layers with a thickness of a few nanometers are common-place in today’s semiconductor devices. Before long, device fabrication methods will reach a point at which the other two device dimensions are scaled down to few tens of nanometers. The total atom count in such deca-nano devices is reduced to a few million. Only a small finite number of “free” electrons will operate such nano-scale devices due to quantized electron energies and electron charge. This work demonstrates that the simulation of electronic structure and electron transport on these length scales must not only be fundamentally quantum mechanical, but it must also include the atomic granularity of the device. Various elements of the theoretical, numerical, and software foundation of the prototype development of a Nanoelectronic Modeling tool (NEMO 3-D) which enables this class of device simulation on Beowulf cluster computers are presented. The electronic system is represented in a sparse complex Hamiltonian matrix of the order of hundreds of millions. A custom parallel matrix vector multiply algorithm that is coupled to a Lanczos and/or Rayleigh- Ritz eigenvalue solver has been developed. Benchmarks of the parallel electronic structure and the parallel strain calculation performed on various Beowulf cluster computers and a SGI Origin 2000 are presented. The Beowulf cluster benchmarks show that the competition for memory access on dual CPU PC boards renders the utility of one of the CPUs useless, if the memory usage per node is about 1-2 GB. A new strain treatment for the sp3s∗ and sp3d5s∗ tight-binding models is developed and parameterized for bulk material properties of GaAs and InAs. The utility of the new tool is demonstrated by an atomistic analysis of the effects of disorder in alloys. In particular bulk InxGa1−xAs and In0.6Ga0.4As quantum dots are examined. The quantum dot simulations show that the random atom configurations in the alloy, without any size or shape variations can lead to optical transition energy variations of several meV. The electron and hole wave functions show significant spatial variations due to spatial disorder indicating variations in electron and hole localization

Enhancing the performance of low concentrating photovoltaics via spectral conversion

The spectral mismatch between the incoming solar spectrum and photovoltaic cells is a fundamental factor which curtails their efficiencies. Through luminescent processes, known as spectral conversion, the wavelengths of the incident sunlight may be changed to better match the optimal values for charge carrier generation by the solar cell. There are three means by which this can occur: upconversion, downconversion and luminescent downshifting, whereby two low energy photons can combine into one of a higher energy, one high energy photon can split its energy into two lower energy ones and a single high energy photon can reduce its energy, respectively. Collectively, these processes have attracted interest as an area of research for their application to solar cells as a method to enhance PV device performance, an important technological challenge to aid in the transition to a decarbonised economy. In this thesis, particles with spectral conversion properties are incorporated into two kinds of novel solar PV devices of relevance to the emerging and building integrated photovoltaic technology sectors, 3D static SEH concentrator photovoltaic modules with potential for building integration and high stability dye sensitized solar cells. Following an introduction to the topic, concisely discussing the underlying mechanisms of each spectral conversion process, and conducting a literature review which catalogues the evolution of state-of-the-art results from the field, experiments are designed to test two candidate spectral conversion materials (Sr4Al14O25: Eu2+, Dy3+ and NaYF4: Er3+, Yb3+) on silicon PV and dye sensitized solar cells, both with and without SEH concentrators. Under an A+A+A+ solar simulator at 1000 W/m2, the power conversion efficiency of silicon PV devices improved up to 11.1% relative to controls through the addition of these materials. At lower irradiances and compared to cells without concentrators, the relative efficiency gains were more pronounced and external quantum efficiency (EQE) measurements suggested spectral conversion was potentially responsible for these enhancements. For a large scale BICPV system, a simple analysis showed cost per watt could fall by up to 8.1% and power output increase from 19.3 to 21.4 W/m2 through this approach. For the dye sensitized solar cells a 53.4% efficiency enhancement (relative to un-doped controls) was achieved with a potential cost reduction of 39.6%. Finally, simple optical models (including one developed in-house) and a statistical analysis are used to justify the findings and develop understanding of the physical processes behind the results, while conclusions are drawn with regards to the future outlook of this approach and its impact on the drive towards lower cost sources of clean electricity

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980