Abstract A neural network approach is presented for transform image coding. It is shown that the three steps in the conventional transform image coding, i.e. the unitary transform of spatial domain image data, the quantization of the transform domain data and the binary coding of the quantized data, can be unified into a one‐step optimization problem. Then, the optimization problem is solved by an appropriately constructed Hopfield neural network whose input is the spatial domain image data and whose output is binary codes. A practical circuit implementation is given to perform the transform image coding. the circuit has rM 2 neurons, where r is the bit‐rate, in bit/pixel, of the coding and M 2 is the size of the images. Each neuron consists of only a non‐linear voltage amplifier, a linear voltage‐controlled current source, a d.c. current source, a linear passive resistor, a linear passive capacitor, and a weighted voltage summer which can be made of a single op amp with some linear passive resistors. Moreover, each neuron is locally connected with no more than b ‐ 1 other neurons by wires, where b is the maximum bit allocated to a transform domain coefficient. Therefore, our proposed approach is particularly suitable for low‐bit‐rate image coding and VLSI implementation. Furthermore, the analogue and parallel nature of our approach matches perfectly the high‐speed requirement of real‐time image coding.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
This article returns to the social history of African Americans to show that a ghetto is not simply a conglomeration of poor families or a spatial accumulation of undesirable social conditions (income deprivation, housing blight, or endemic crime and other disruptive behaviors), but an institutional form, an instrument of ethnoracial closure and power whereby an urban population deemed disreputable and dangerous is at once secluded and controlled. Such compulsory institutional encasement founded on spatial confinement has been noted by every major Afro-American student of the black urban predicament in the twentieth century, from W. E. B. Du Bois and St. Clair Drake and Horace Cayton to E. Franklin Frazier, Kenneth Clark and Oliver Cromwell Cox. The elision of the ethnoracial dimension of urban relegation in the academic tale of the “ghetto underclassâ€? emerging in the 1980s, which redefines the “ghettoâ€? in strict income terms, is revealed to express the mounting suppression of race in policy-oriented research as the “War on Povertyâ€? gave way to the “War on Welfareâ€?.
Characteristics of fatigue-crack propagation behavior are reviewed for recently developed commercial aluminum-lithium alloys, with emphasis on the underlying micromechanisms associated with crack advance and their implications to damage-tolerant design. Specifically, crack-growth kinetics in Alcoa 2090-T8E41, Alcan 8090 and 8091, and Pechiney 2091 alloys, and in certain powder-metallurgy alloys, are examined as a function of microstructure, plate orientation, temperature, crack size, load ratio and loading sequence. In general, it is found that growth rates for long (> 10 mm) cracks are nearly 2--3 orders of magnitude slower than in traditional 2000 and 7000 series alloys at comparable stress-intensity levels. In additions, Al-Li alloys shown enhanced crack-growth retardations following the application of tensile overloads and retain superior fatigue properties even after prolonged exposure at overaging temperatures; however, they are less impressive in the presence of compression overloads and further show accelerated crack-growth behavior for microstructurally-small (2--1000 {mu}m) cracks (some three orders of magnitude faster than long cracks). These contrasting observations are attributed to a very prominent role of crack-tip shielding during fatigue-crack growth in Al-Li alloys, promoted largely by the tortuous and zig-zag nature of the crack-path morphologies. Such crack paths result in locally reduced crack-tip stress intensities, due to crack deflection and consequent crack wedging from fracture-surface asperities (roughness-induced crack closure); however, such mechanisms are far less potent in the presence of compressive loads, which act to crush the asperities, and for small cracks, where the limited crack wake severely restricts the shielding effect. 50 refs., 21 figs.
Public demand for clean and sustainable water sources drives the need for skilled hydrogeologist who specialize in surface and subsurface water flow. Hydrogeologists must integrate three-dimensional data from maps, wells, field sites, and geologic models to predict the movement of water through the subsurface. Research in other STEM disciplines has shown that targeted training of relevant spatial thinking skills can improve student persistence and retention, especially among women and students of color. Because the specific spatial thinking skills relevant to practicing hydrogeology have not yet been documented, best practices to inform hydrogeology curricula are lacking. This situation hampers efforts to train students for careers in hydrogeology and our response to the need for clean and sustainable water. Our project seeks to identify and characterize the specific spatial thinking skills and knowledge that hydrogeologists use when solving water and contaminant flow problems, and to understand how students use (or do not use) these skills when learning hydrogeology in the classroom. Characterizing these skills is a critical first step toward creating curricular materials that will improve the preparation of diverse and capable hydrogeologists ready to respond to the challenges of a changing world. This presentation will present our work and findings from the first year of our project and focus on characterization of spatial thinking skills relevant to practicing hydrogeology using data collected from expert hydrogeologists from government, consulting, industry, and academia.
The disclosure relates to metal organic frameworks or isoreticular metal organic frameworks, methods of production thereof, and methods of use thereof.
