Development of a Power Electronics Controller for the Advanced Stirling Radioisotope Generator

Under a U.S. Department of Energy program for radioisotope power systems, Lockheed Martin is developing an Engineering Unit of the Advanced Stirling Radioisotope Generator (ASRG). This is an advanced version of the previously reported SRG110 generator. The ASRG uses Advanced Stirling Convertors (ASCs) developed by Sunpower Incorporated under a NASA Research Announcement contract. The ASRG makes use of a Stirling controller based on power electronics that eliminates the tuning capacitors. The power electronics controller synchronizes dual-opposed convertors and maintains a fixed frequency operating point. The controller is single-fault tolerant and uses high-frequency pulse width modulation to create the sinusoidal currents that are nearly in phase with the piston velocity, eliminating the need for large series tuning capacitors. Sunpower supports this effort through an extension of their controller development intended for other applications. Glenn Research Center (GRC) supports this effort through system dynamic modeling, analysis and test support. The ASRG design arrived at a new baseline based on a system-level trade study and extensive feedback from mission planners on the necessity of single-fault tolerance. This paper presents the baseline design with an emphasis on the power electronics controller detailed design concept that will meet space mission requirements including single fault tolerance

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

Analogy making and the structure of implied volatility skew

An analogy based option pricing model is put forward. If option prices are determined in accordance with the analogy model, and the Black Scholes model is used to back-out implied volatility, then the implied volatility skew arises, which flattens as time to expiry increases. The analogy based stochastic volatility and the analogy based jump diffusion models are also put forward. The analogy based stochastic volatility model generates the skew even when there is no correlation between the stock price and volatility processes, whereas, the analogy based jump diffusion model does not require asymmetric jumps for generating the skew

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

ASPEN Revisited: The Challenge of Nuclear Propulsion for ETO

37th AIAA/ ASME/SAE/ASEE Joint Propulsion Conference and Exhibit Salt Lake City, UT, July 8-11, 2001.ASPEN was a study conducted by Los Alamos National Labs in the early 1960s to examine the benefits of using a Nuclear Thermal Rocket (NTR) for Earth-to-Orbit (ETO) single-stage launch vehicle applications. Using the analysis methods and assumptions of the time, this formerly classified study showed that a significant performance potential might be derived from using NTR engines for the final acceleration phase to orbit (air-breathing engines were used to Mach 11). Given the increased NASA interest in low-cost reusable space transportation, the ASPEN concept has been revisited using contemporary design assumptions and conceptual analysis techniques. The present analysis concludes with a more pessimistic view of NTR propulsion for ETO applications. Aerodynamic drag for the ASPEN configuration was found to be significantly more than that calculated in the original study. The resultant vehicle thrust-to-drag ratio is lower than necessary for high acceleration during the air-breathing acceleration phases. In addition, the NTR reactor power requirements are daunting. In most cases, reactor powers over 10 GW are required. Even with very aggressive assumptions (25 percent drag reduction and NTR thrust-to-weight ratio of 10, including shielding) a 500,000 lb gross weight ASPEN-like vehicle was found to only have a payload mass fraction of 1.6 percent. This is significantly less than the 6 to 15 percent payload mass fractions claimed in the original ASPEN study

ASPEN Revisited: The Challenge of Nuclear Propulsion for ETO

37th AIAA/ ASME/SAE/ASEE Joint Propulsion Conference and Exhibit Salt Lake City, UT, July 8-11, 2001.ASPEN was a study conducted by Los Alamos National Labs in the early 1960s to examine the benefits of using a Nuclear Thermal Rocket (NTR) for Earth-to-Orbit (ETO) single-stage launch vehicle applications. Using the analysis methods and assumptions of the time, this formerly classified study showed that a significant performance potential might be derived from using NTR engines for the final acceleration phase to orbit (air-breathing engines were used to Mach 11). Given the increased NASA interest in low-cost reusable space transportation, the ASPEN concept has been revisited using contemporary design assumptions and conceptual analysis techniques. The present analysis concludes with a more pessimistic view of NTR propulsion for ETO applications. Aerodynamic drag for the ASPEN configuration was found to be significantly more than that calculated in the original study. The resultant vehicle thrust-to-drag ratio is lower than necessary for high acceleration during the air-breathing acceleration phases. In addition, the NTR reactor power requirements are daunting. In most cases, reactor powers over 10 GW are required. Even with very aggressive assumptions (25 percent drag reduction and NTR thrust-to-weight ratio of 10, including shielding) a 500,000 lb gross weight ASPEN-like vehicle was found to only have a payload mass fraction of 1.6 percent. This is significantly less than the 6 to 15 percent payload mass fractions claimed in the original ASPEN study

Moon-based Advanced Reusable Transportation Architecture

37th AIAA/ASME/SAE/ASEE Joint Propulsion Conference And Exhibit Salt Lake City, UT, July 8-11, 2001.Abstract: The Moon-based Advanced Reusable Transportation Architecture (MARTA) Project conducted an in-depth investigation of possible Low Earth Orbit (LEO) to lunar surface transportation systems capable of sending both astronauts and large masses of cargo to the Moon and back. The goal of this project was to create a profitable venture with an Internal Rate of Return (IRR) of 25%. The architecture was quickly narrowed down to a traditional chemical rocket using a liquid oxygen and liquid hydrogen. However, three additional technologies identified as potentially cost saving were: aerobraking, in-situ resource utilization (ISRU), and a mass driver on the lunar surface. The vehicle was modeled using the Simulated Probabilistic Parametric Lunar Architecture Tool (SPPLAT) that incorporated several different engineering disciplines. This tool used ISRU propellant cost, a dry weight reduction due to improved materials technology, and vehicle engine specific impulse as inputs and provides vehicle dry weight, total propellant used per trip, and price to charge the customer in order to guarantee an IRR of 25% as outputs. Estimation error, market growth, and launch cost uncertainty were also considered. The results of the project show that the desired operation is possible using current technology. Based on the stipulation that the venture be profitable, the price to charge the customer was highly dependent on ISRU propellant cost and relatively insensitive to the other inputs. With the best estimate of ISRU cost set at $1000/kg, the resulting price to charge the customer was$2600/kg of payload from LEO to the lunar surface. If ISRU cost can be reduced to $160/kg, the price to the customer is reduced to just$800/kg of payload. Additionally, the mass driver only proved to be cost effective at an ISRU propellant cost greater than $250/kg, although it reduced total propellant used by 35%