Development of an evaluation technique for strapdown guidance systems Interim scientific report

Evaluation technique to measure performance of strapdown guidance systems designed for unmanned interplanetary mission

Development of an evaluation technique for strapdown guidance systems Interim report, 1 Feb. 1968 - 1 Feb. 1969

Evaluation techniques for astrionics systems using aided strapdown inertial guidanc

Comparative analysis of techniques for evaluating the effectiveness of aircraft computing systems

Performability analysis is a technique developed for evaluating the effectiveness of fault-tolerant computing systems in multiphase missions. Performability was evaluated for its accuracy, practical usefulness, and relative cost. The evaluation was performed by applying performability and the fault tree method to a set of sample problems ranging from simple to moderately complex. The problems involved as many as five outcomes, two to five mission phases, permanent faults, and some functional dependencies. Transient faults and software errors were not considered. A different analyst was responsible for each technique. Significantly more time and effort were required to learn performability analysis than the fault tree method. Performability is inherently as accurate as fault tree analysis. For the sample problems, fault trees were more practical and less time consuming to apply, while performability required less ingenuity and was more checkable. Performability offers some advantages for evaluating very complex problems

Effectiveness evaluation of STOL transport operations

A short-takeoff and landing (STOL) systems simulation model has been developed and implemented in a computer code (known as STOL OPS) which permits evaluation of the operation of a STOL aircraft and its avionics in a commercial airline operating environment. STOL OPS concentrated on the avionics functions of navigation, guidance, control, communication, hazard aviodance, and systems management. External world factors influencing the operation of the STOL aircraft include each airport and its geometry, air traffic at each airport, air traffic control equipment and procedures, weather (including winds and visibility), and the flight path between each airport served by the route. The development of the STOL OPS program provides NASA a set of computer programs which can be used for detailed analysis of a STOL aircraft and its avionics and permit establishment of system requirements as a function of airline mission performance goals

Development of an evaluation technique for interplanetary mission astrionics Interim scientific report

Evaluating astrionics for interplanetary flyby missions using penalty function

Coexistence of Two Rare Sarcomas: Primary Leiomyosarcoma of Bone and Epithelioid Hemangioendothelioma of the Liver

A 33-year-old woman sought medical attention for a painful swelling of the left ankle. Plain radiographs revealed an osteolytic lesion involving the left distal tibia. An excisional biopsy provided the diagnosis of leiomyosarcoma in the tibia. A staging work-up was performed and an abdominal CT showed 4 liver hypodense lesions in both lobes with peripheral contrast enhancement. A liver biopsy confirmed the diagnosis of epithelioid hemangioendothelioma of the liver. No association between these two entities has been described before. This case introduces the importance of the pathological confirmation of apparent metastatic lesions in low grade sarcomas and provides a review of the literature of both tumours

Modeling oscillatory Microtubule--Polymerization

Polymerization of microtubules is ubiquitous in biological cells and under certain conditions it becomes oscillatory in time. Here simple reaction models are analyzed that capture such oscillations as well as the length distribution of microtubules. We assume reaction conditions that are stationary over many oscillation periods, and it is a Hopf bifurcation that leads to a persistent oscillatory microtubule polymerization in these models. Analytical expressions are derived for the threshold of the bifurcation and the oscillation frequency in terms of reaction rates as well as typical trends of their parameter dependence are presented. Both, a catastrophe rate that depends on the density of {\it guanosine triphosphate} (GTP) liganded tubulin dimers and a delay reaction, such as the depolymerization of shrinking microtubules or the decay of oligomers, support oscillations. For a tubulin dimer concentration below the threshold oscillatory microtubule polymerization occurs transiently on the route to a stationary state, as shown by numerical solutions of the model equations. Close to threshold a so--called amplitude equation is derived and it is shown that the bifurcation to microtubule oscillations is supercritical.Comment: 21 pages and 12 figure

Beta-delayed proton emission in the 100Sn region

Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was studied at the National Superconducting Cyclotron Laboratory. The nuclei were produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be target. Beam purification was provided by the A1900 Fragment Separator and the Radio Frequency Fragment Separator. The fragments of interest were identified and their decay was studied with the NSCL Beta Counting System (BCS) in conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing, 98Inm and 99In were identified as beta-delayed proton emitters, with branching ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for 89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9 -1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for 101Sn was deduced with higher precision than previously reported. The impact of the newly measured bp values on the composition of the type-I X-ray burst ashes was studied.Comment: 15 pages, 14 Figures, 4 Table

Impact of Pycnonuclear Fusion Uncertainties on the Cooling of Accreting Neutron Star Crusts

The observation of X-rays during quiescence from transiently accreting neutron stars provides unique clues about the nature of dense matter. This, however, requires extensive modeling of the crusts and matching the results to observations. The pycnonuclear fusion reaction rates implemented in these models are theoretically calculated by extending phenomenological expressions and have large uncertainties spanning many orders of magnitude. We present the first sensitivity studies of these pycnonuclear fusion reactions in realistic network calculations. We also couple the reaction network with the thermal evolution code dStar to further study their impact on the neutron star cooling curves in quiescence. Varying the pycnonuclear fusion reaction rates alters the depth at which nuclear heat is deposited although the total heating remains constant. The enhancement of the pycnonuclear fusion reaction rates leads to an overall shallower deposition of nuclear heat. The impurity factors are also altered depending on the type of ashes deposited on the crust. These total changes correspond to a variation of up to 9 eV in the modeled cooling curves. While this is not sufficient to explain the shallow heat source, it is comparable to the observational uncertainties and can still be important for modeling the neutron star crust.Comment: AASTeX63, 11 pages with 9 figure