Shared memory for a fault-tolerant computer

A system is described for sharing a memory in a fault-tolerant computer. The memory is under the direct control and monitoring of error detecting and error diagnostic units in the fault-tolerant computer. This computer verifies that data to and from the memory is legally encoded and verifies that words read from the memory at a desired address are, in fact, actually delivered from that desired address. The means are provided for a second processor, which is independent of the direct control and monitoring of the error checking and diagnostic units of the fault-tolerant computer, and to share the memory of the fault-tolerant computer. Circuitry is included to verify that: (1) the processor has properly accessed a desired memory location in the memory; (2) a data word read-out from the memory is properly coded; and (3) no inactive memory was erroneously outputting data onto the shared memory bus

Runoff and Erosion as Affected by Sorghum and Soybean Residue

A rainfall simulator was used to measure the effects of varying rates of sorghum and soybean residue on runoff and erosion. In general, increased surface cover caused reduced runoff, sediment concentration and soil loss. Substantial reductions in erosion resulted from the use of small amounts of crop residue. Regression equations were obtained which related surface cover to residue mass. Equations describing relative runoff, sediment concentration and soil loss as a function of surface cover were also developed. Runoff, sediment concentration and soil loss were all found to be highly correlated to surface cover

Size Distribution of Sediment as Affected by Surface Residue and Slope Length

Runoff samples for determination of size distribution of sediment were collected under simulated rainfall conditions at selected downslope distances on plots covered with sorghum and soybean residue at rates ranging from 0.00 to 6.73 t/ha . The effects of surface residue and slope length on size distribution of sediment were evaluated. Substantial movement of sediment in the form of aggregates was found for each of the residue treatments. Significant differences in size distribution of sediment occurred between residue treatments. For a given residue rate, differences in sediment size distribution were found between sorghum and soybean residue. Size distribution of sediment was also determined to be significantly different at selected downslope distances

Hydraulic Conditions Required to Move Unanchored Residue Materials

Hydraulic conditions required to initiate movement of unanchored residue materials are identified in the present study. Selected amounts of corn, cotton, pine needles, sorghum, soybean, sunflower, and wheat residue are placed in a flume on a sand surface, and flow is then introduced at the top of the flume in progressive increments. The discharge rate and flow velocity necessary to cause residue movement are determined. The ratio of critical flow depth to residue diameter, critical Reynolds number, critical shear stress, dimensionless shear stress, and boundary Reynolds number are calculated from hydraulic measurements. Regression equations are developed to relate dimensionless shear stress to boundary Reynolds number and residue diameter. Boundary Reynolds number, in turn, is related to residue diameter and cover. Close agreement is found between predicted and actual parameter values obtained from the regression relations. The regression equations can be used to estimate the beginning of motion for other residue materials if residue diameter and cover are known

Layered Metals Fabrication Technology Development for Support of Lunar Exploration at NASA/MSFC

NASA's human exploration initiative poses great opportunity and risk for missions to the Moon and beyond. In support of these missions, engineers and scientists at the Marshall Space Flight Center are developing technologies for ground-based and in-situ fabrication capabilities utilizing provisioned and locally-refined materials. Development efforts are pushing state-of-the art fabrication technologies to support habitat structure development, tools and mechanical part fabrication, as well as repair and replacement of ground support and space mission hardware such as life support items, launch vehicle components and crew exercise equipment. This paper addresses current fabrication technologies relative to meeting targeted capabilities, near term advancement goals, and process certification of fabrication methods

An autosegmental approach to phonological phenomena in Shilluk.

Shilluk is a Western Nilotic language spoken in southern Sudan. Previous works on this language have failed to adequately capture the phonological and morphological systems of the language. An Autosegmental approach employed within a framework based upon the tenets of Lexical Phonology, allows the various aspects of Shilluk phonology to be separated in an insightful way. Thus, the vowel and consonant harmony systems, the tonal system, and the syllable structure may be dealt with independently. The thesis comprises six chapters: 1, Introduction, 2. Phonetics and Phonology, 3. The Representation of Lexical Items, 4. Syllable Structure, 5. Lexical Levels of Derivation, and 6. Summary. Chapter 2 provides a relatively 'autonomous' account of the consonants, vowels (including length), and tone. Chapter 3 presents evidence for the claim that it is necessary to set up independent underlying representations for the stems of singular and plural nouns, as well as for Transitive verb forms. Issues covered in this chapter are tone and the harmony systems - vowel harmony, vowel and consonant harmony, and consonant harmony. Chapter Four completes the argument for independent representations with a discussion of syllable structure. This chapter shows how syllable structure constraints may be invoked to account for surface vowel length alternations. In turn, this chapter adds another argument for the claim that most lexical items require dual (independent) underlying representations. The material in this chapter demonstrates that processes motivated by syllable structure make it the most influential factor in Shilluk phonology. In Chapter 5, the discussion turns to the ordering of levels within the Lexicon. By combining all the tone and syllable structure rules, it is possible to establish the presence of three levels within the Lexicon. A summary of all the rules developed in the thesis are given in the sixth chapter along with comments on the implications of this study with regard to language acquisition. Some suggestions are also made for further study

A Simplified Equation for Modeling Sediment Transport Capacity

Sediment transport capacity for shallow overland flow was represented as a quadratic function of downslope distance using the assumption of a linear increase in overland flow discharge with downslope distance and an approximation to the Yalin equation for sediment transport capacity. The simplified equation for sediment transport applies to complex topography having uniform soil and management characteristics. The simplified equation accurately approximated the Yalin equation when calibrated using the average of the hydraulic shear stresses at the end of a constant slope reference profile and the end of the actual profile. The simplified equation is useful in deriving closed-form solutions to the governing erosion equations for steady state conditions and reduces the computational time when numerical solutions are required

Size Distribution of Sediment as Affected by Corn Residue

Size distribution of sediment was measured under simulated rainfall conditions at selected downslope distances on plots with corn residue rates ranging from 0.00 to 6.73 t/ha. The formation of rills caused increases in the percentage of larger sized sediment material. Greater surface cover usually resulted in an increase in the percentage of smaller sized sediment. Considerable variation in the size of sediment from both rill and interrill areas was found with downslope distance. On interrill regions, the presence of residue served to reduce sediment size along the entire plot length. Transport of aggregated sediment occurred on each of the residue treatments

A Simplified Equation for Modeling Sediment Transport Capacity

Sediment transport capacity for shallow overland flow was represented as a quadratic function of downslope distance using the assumption of a linear increase in overland flow discharge with downslope distance and an approximation to the Yalin equation for sediment transport capacity. The simplified equation for sediment transport applies to complex topography having uniform soil and management characteristics. The simplified equation accurately approximated the Yalin equation when calibrated using the average of the hydraulic shear stresses at the end of a constant slope reference profile and the end of the actual profile. The simplified equation is useful in deriving closed-form solutions to the governing erosion equations for steady state conditions and reduces the computational time when numerical solutions are required