State-plane trajectories used to observe and control the behavior of a voltage step-up dc-to-dc converter

State-plane analysis techniques are employed to study the voltage step up energy storage dc-to-dc converter. Within this framework, an example converter operating under the influence of a constant on time and a constant frequency controller is examined. Qualitative insight gained through this approach is used to develop a conceptual free running control law for the voltage step up converter which can achieve steady state operation in one on/off cycle of control. Digital computer simulation data is presented to illustrate and verify the theoretical discussions presented

The origins of radial fracture systems and associated large lava flows on Venus

Magellan images have revealed the existence of systems of radial fractures on venus that are very similar in form to terrestrial dike swarms such as the Mackenzie swarm in Northern Canada. The association of many of the fracture systems with lava flows, calderas, and volcanic edifices further support the idea of a dike emplacement origin. A global survey of the Magellan images has allowed the location of 300 such fracture systems. Two types of fracture systems are defined. A series of models were developed to simulate the emplacement of dikes on Venus. Observations of fracture lengths and widths were then used to constrain the emplacement conditions. The model results show that the great length and relatively large width of the fractures can only be explained if the dikes that produce them were emplaced in high driving pressure (pressure buffered) conditions. Such conditions imply high rates of melt production, which is consistent with the melt being derived directly from a plume head. We have recently modeled the vertical emplacement of a dike from the top of a mantle plume and calculated the eruption rates such a dike would produce on reaching the surface. This modeling shows that eruption rates of approximately 0.1 cu km/hr can readily be generated by such a dike, consistent with the above results. However, the sensitivity of the model to dike width and therefore driving pressure means that eruption rates from dikes emplaced from the base of the crust or the head of a mantle plume could be orders of magnitude higher than this. Clearly, therefore, the model needs to be refined in order to better constrain eruption conditions. However, it is worth noting here that the initial results do show that even for moderate dike widths, eruption rates could be at least on the order of those estimated for terrestrial flood basalts

The Late Prehistoric of the East Fork of the Trinity River

Over the last 42 years, the authors have studied in detail the sites and archeological remains ascribed to the Late Prehistoric period of the East Fork of the Trinity River and its tributaries. This includes 20 major sites and a larger number of smaller campsites that occur within a 75 km by 15 km north-south corridor from Collin County in the north to northwestern Kaufman County in the south. As part of this study, we have accessed and examined all known extant collections from previous investigations with a combined artifact assemblage of nearly 32,000 specimens. In addition, we obtained access to the unpublished field notes and maps from many previous researchers and combined them with our own field and laboratory observations. The results of this study confirms the conclusion of both Bruseth and Martin and Prikryl that the \textit{Wylie Focus}, as originally proposed by Stephenson, is an outdated concept. A new chronological sequence consisting of a Woodland period followed by two Late Prehistoric period phases is proposed. In detailing the proposed new sequences, extensive information on each major site, site features such as the distinctive rim-and-pit structures, burials, hearths and caches, and the diagnostic artifacts that characterize each cultural phase are provided. We also detail how the Late Prehistoric of the East Fork is a unique culture, similar but yet distinctly different from the surrounding sites including Bird Point Island (41FT201) and Adams Ranch (41NV177) in Freestone and Navarro counties

Ceramic Types from Late Prehistoric Sites along the East Fork of the Trinity River

Ceramics are one of the key diagnostic artifacts that define the Late Prehistoric culture of the peoples that lived along the East Fork of the Trinity and its tributaries. We are completing a 42 year re evaluation of the Late Prehistoric period of the area and have st udied nearly 32,000 artifacts, of which over 10,200 are ceramic sherds. From this study, 20 distinct ceramic types have been recognized. Plain ware, both shell tempered and sandy paste/grog tempered, are the predominant ceramic types present, comprising ov er 90 percent of the total ceramic assemblage. While there is little direct evidence for indigenous manufacture, the abundance of these types suggests they were produced locally. Lesser quantities of decorated ware of distinct Caddo ceramic types from the Red River and East Texas suggest they are likely the product of exchange. There is also a small amount of Puebloan material indicative of a longer distance exchange

A digital computer simulation and study of a direct-energy-transfer power-conditioning system

A digital computer simulation technique, which can be used to study such composite power-conditioning systems, was applied to a spacecraft direct-energy-transfer power-processing system. The results obtained duplicate actual system performance with considerable accuracy. The validity of the approach and its usefulness in studying various aspects of system performance such as steady-state characteristics and transient responses to severely varying operating conditions are demonstrated experimentally

The variable polarity plasma arc welding process: Its application to the Space Shuttle external tank

The technical history of the variable polarity plasma arc (VPPA) welding process being introduced as a partial replacement for the gas shielded tungsten arc process in assembly welding of the space shuttle external tank is described. Interim results of the weld strength qualification studies, and plans for further work on the implementation of the VPPA process are included

Fast-response free-running frequency-stabilized dc-to-dc converter employing a state plane-trajectory control law

Implementations of a state-plane-trajectory control law for energy storage dc-to-dc converters are presented. Performance characteristics of experimental voltage step-up converter systems employing these implementations are reported and compared to theoretical predictions