Implementation of an intelligent control system

A laboratory testbed facility which was constructed at NASA LeRC for the development of an Intelligent Control System (ICS) for reusable rocket engines is described. The framework of the ICS consists of a hierarchy of various control and diagnostic functions. The traditional high speed, closed-loop controller resides at the lowest level of the ICS hierarchy. Above this level resides the diagnostic functions which identify engine faults. The ICS top level consists of the coordination function which manages the interaction between an expert system and a traditional control system. The purpose of the testbed is to demonstrate the feasibility of the OCS concept by implementing the ICS as the primary controller in a simulation of the Space Shuttle Main Engine (SSME). The functions of the ICS which are implemented in the testbed are as follows: an SSME dynamic simulation with selected fault mode models, a reconfigurable controller, a neural network for sensor validation, a model-based failure detection algorithm, a rule based failure detection algorithm, a diagnostic expert system, an intelligent coordinator, and a user interface which provides a graphical representation of the event occurring within the testbed. The diverse nature of the ICS has led to the development of a distributed architecture consisting of specialized hardware and software for the implementation of the various functions. This testbed is made up of five different computer systems. These individual computers are discussed along with the schemes used to implement the various ICS components. The communication between computers and the timing and synchronization between components are also addressed

ABA and Oxygen Crosstalk During Seed Development

No abstract availabl

Teaching varies with task complexity in wild chimpanzees

Understanding social influences on how apes acquire tool behaviors can help us model the evolution of culture and technology in humans. Humans scaffold novice tool skills with diverse strategies, including the transfer of tools between individuals. Chimpanzees transfer tools, and this behavior meets criteria for teaching. However, it is unclear how task complexity relates to this form of helping. Here, we find differences between 2 wild chimpanzee populations in rate, probability, and types of tool transfer during termite gathering. Chimpanzees showed greater helping in the population where termite gathering is a more complex tool task. In wild chimpanzees, as in humans, regular and active provisioning of learning opportunities may be essential to the cultural transmission of complex skills.Cumulative culture is a transformative force in human evolution, but the social underpinnings of this capacity are debated. Identifying social influences on how chimpanzees acquire tool tasks of differing complexity may help illuminate the evolutionary origins of technology in our own lineage. Humans routinely transfer tools to novices to scaffold their skill development. While tool transfers occur in wild chimpanzees and fulfill criteria for teaching, it is unknown whether this form of helping varies between populations and across tasks. Applying standardized methods, we compared tool transfers during termite gathering by chimpanzees in the Goualougo Triangle, Republic of Congo, and in Gombe, Tanzania. At Goualougo, chimpanzees use multiple, different tool types sequentially, choose specific raw materials, and perform modifications that improve tool efficiency, which could make it challenging for novices to manufacture suitable tools. Termite gathering at Gombe involves a single tool type, fishing probes, which can be manufactured from various materials. Multiple measures indicated population differences in tool-transfer behavior. The rate of transfers and probability of transfer upon request were significantly higher at Goualougo, while resistance to transfers was significantly higher at Gombe. Active transfers of tools in which possessors moved to facilitate possession change upon request occurred only at Goualougo, where they were the most common transfer type. At Gombe, tool requests were typically refused. We suggest that these population differences in tool-transfer behavior may relate to task complexity and that active helping plays an enhanced role in the cultural transmission of complex technology in wild apes

Stability of Transparent Spherically Symmetric Thin Shells and Wormholes

The stability of transparent spherically symmetric thin shells (and wormholes) to linearized spherically symmetric perturbations about static equilibrium is examined. This work generalizes and systematizes previous studies and explores the consequences of including the cosmological constant. The approach shows how the existence (or not) of a domain wall dominates the landscape of possible equilibrium configurations.Comment: 12 pages, 7 figures, revtex. Final form to appear in Phys. Rev.

Roles of Intra-fruit Oxygen and Carbon Dioxide in Controlling Pepper (Capsicum annuum L.) Seed Development and Storage Reserve Deposition

Seeds developing within a locular space inside hollow fruit experience chronic exposure to a unique gaseous environment. Using two pepper cultivars, `Triton\u27 (sweet) and `PI 140367\u27 (hot), we investigated how the development of seeds is affected by the gases surrounding them. The atmospheric composition of the seed environment was characterized during development by analysis of samples withdrawn from the fruit locule with a gas-tight syringe. As seed weight plateaued during development, the seed environment reached its lowest O2 concentration (19%) and highest CO2 concentration (3%). We experimentally manipulated the seed environment by passing different humidified gas mixtures through the fruit locule at a rate of 60 to 90 mL·min-1. A synthetic atmosphere containing 3% CO2, 21% O2, and 76% N2 was used to represent a standard seed environment. Seeds developing inside locules supplied with this mixture had enhanced average seed weight, characterized by lower variation than in the no-flow controls due to fewer low-weight seeds. The importance of O2 in the seed microenvironment was demonstrated by reduction in seed weight when the synthetic atmosphere contained only 15% O2 and by complete arrest of embryo development when O2 was omitted from the seed atmosphere. Removal of CO2 from the synthetic atmosphere had no effect on seed weight, however, the CO2-free treatment accelerated fruit ripening by 4 days in the hot pepper. In the sweet peppers, fruit wall starch and sucrose were reduced by the CO2-free treatment. The results demonstrate that accretionary seed growth is being limited in pepper by O2 availability and suggest that variation in seed quality is attributable to localized limitations in O2 supply

Tool transfers are a form of teaching among chimpanzees

Teaching is a form of high-fidelity social learning that promotes human cumulative culture. Although recently documented in several nonhuman animals, teaching is rare among primates. In this study, we show that wild chimpanzees (Pan troglodytes troglodytes) in the Goualougo Triangle teach tool skills by providing learners with termite fishing probes. Tool donors experienced significant reductions in tool use and feeding, while tool recipients significantly increased their tool use and feeding after tool transfers. These transfers meet functional criteria for teaching: they occur in a learner’s presence, are costly to the teacher, and improve the learner’s performance. Donors also showed sophisticated cognitive strategies that effectively buffered them against potential costs. Teaching is predicted when less costly learning mechanisms are insufficient. Given that these chimpanzees manufacture sophisticated, brush-tipped fishing probes from specific raw materials, teaching in this population may relate to the complexity of these termite-gathering tasks

A proposal of a UCN experiment to check an earthquake waves model

Elastic waves with transverse polarization inside incidence plane can create longitudinal surface wave (LSW) after reflection from a free surface. At a critical incidence angle this LSW accumulates energy density, which can be orders of magnitude higher than energy density of the incident transverse wave. A specially arranged vessel for storage of ultracold neutrons (UCN) can be used to verify this effect.Comment: 8 pages 3 figures added a paragraph on vibrations along surface at critical angl

Those wonderful elastic waves

We consider in a simple and general way elastic waves in isotropic and anisotropic media, their polarization, speeds, reflection from interfaces with mode conversion, and surface waves. Reflection of quasi transverse waves in anisotropic media from a free surface is shown to be characterized by three critical angles.Comment: 11 Figures 26 page