Design, Performance, and Complexity of CRC-Aided List Decoding of Convolutional and Polar Codes for Short Messages

Motivated by the need to communicate short control messages in 5G and beyond, this paper carefully designs codes for cyclic redundancy check (CRC)-aided list decoding of tail-biting convolutional codes (TBCCs) and polar codes. Both codes send a 32-bit message using an 11-bit CRC and 512 transmitted bits. We aim to provide a careful, fair comparison of the error performance and decoding complexity of polar and TBCC techniques for a specific case. Specifically, a TBCC is designed to match the rate of a (512, 43) polar code, and optimal 11-bit CRCs for both codes are designed. The paper examines the distance spectra of the polar and TBCC codes, illuminating the different distance structures for the two code types. We consider both adaptive and non-adaptive CRC-aided list decoding schemes. For polar codes, an adaptive decoder must start with a larger list size to avoid an error floor. For rate-32/512 codes with an 11-bit CRC, the optimized CRC-TBCC design achieves a lower total failure rate than the optimized CRC-polar design. Simulations showed that the optimized CRC-TBCC design achieved significantly higher throughput than the optimized CRC-polar design, so that the TBCC solution achieved a lower total failure rate while requiring less computational complexity.Comment: First revision submitted to IEEE Transactions on Communication

Shape Memory Alloys Via Halide-Activated Pack Equilibration

Fabrication of shape memory alloy (SMA) components based on NiTi is challenging due to the precision with which elemental composition and microstructure must be controlled during processing to achieve desired shape memory behavior. Herein, a method to control chemistry in an NiTi SMA via halide-activated pack equilibration (SHAPE) against a constant chemical potential reservoir is described. To demonstrate the efficacy of the SHAPE process, an initially titanium-deficient specimen (pure nickel foam) has been equilibrated against an excess of an intimately mixed two-phase pack (NiTi + Ti2Ni) in the presence of a vapor phase transport agent (iodine). The two-phase pack regulates chemical potentials in this two-component system in accordance with Gibbs\u27 phase rule. Ti-rich NiTi foams thus produced exhibit reproducible and well-defined phase transformation behaviors. The SHAPE process is advantageous for the fabrication of shape memory components of varying areal dimension, shape, and/or complexity owing to independence of the equilibrium state of the system from either the initial state of the specimen or the details of the process kinetics. Current limitations and prospects for the application of this method to improve the quality of SMA components are briefly discussed

Use of Time in Household Activities by a Selected Group of Oklahoma Homemakers

Home Management, Equipment and Family Economic

Assessing impacts of alternative livestock management practices: raging debates and a role for science

Grazing of domestic livestock is the most pervasive and persistent human impact on the grasslands and shrublands of the Colorado Plateau. Impacts on ecosystem function and biological diversity arc thought to be great, but few studies have attempted to characterize such effects and compare the impacts of alternative livestock management practices. The dearth of pertinent, defensible information has contributed to the polarization of ranching and environmental interests, and has exacerbated what is one of the most contentious social issues in the southwestern USA. We discuss the role of ecological science in deriving and disseminating information that will help focus and perhaps resolve the impasse over grazing impacts and other natural resource issues. Specifically, we describe results of our involvement in "management teams" that include ranchers, environmentalists, public servants, and interested citizens, and how this collaborative process has helped shape an experimental research program that would be impossible to execute without the involvement of divergent interests in the grazing debate. Claims of various interest groups are reformulated as testable hypotheses, and a research design is presented

The use of small angle neutron scattering with contrast matching and variable adsorbate partial pressures in the study of porosity in activated carbons

The porosity of a typical activated carbon is investigated with small angle neutron scattering (SANS), using the contrast matching technique, by changing the hydrogen/deuterium content of the absorbed liquid (toluene) to extract the carbon density at different scattering vector (Q) values and by measuring the p/p0 dependence of the SANS, using fully deuterated toluene. The contrast matching data shows that the apparent density is Q-dependent, either because of pores opening near the carbon surface during the activation processor or changes in D-toluene density in nanoscale pores. For each p/p0 value, evaluation of the Porod Invariant yields the fraction of empty pores. Hence, comparison with the adsorption isotherm shows that the fully dry powder undergoes densification when liquid is added. An algebraic function is developed to fit the SANS signal at each p/p0 value hence yielding the effective Kelvin radii of the liquid surfaces as a function of p/p0. These values, when compared with the Kelvin Equation, show that the resultant surface tension value is accurate for the larger pores but tends to increase for small (nanoscale) pores. The resultant pore size distribution is less model-dependent than for the traditional methods of analyzing the adsorption isotherms

Parasite diversity and ecology in a model species, the guppy (Poecilia reticulata) in Trinidad

The guppy (Poecilia reticulata) is a model species in ecology and evolution. Many studies have examined effects of predators on guppy behaviour, reproduction, survival strategies, feeding and other life-history traits, but few have studied variation in their parasite diversity. We surveyed parasites of 18 Trinidadian populations of guppy, to provide insight on the geographical mosaic of parasite variability, which may act as a source of natural selection acting on guppies. We found 21 parasite species, including five new records for Trinidad. Spatial variation in parasite diversity was significantly higher than that of piscine predators, and significant variation in parasite richness among individuals and populations was correlated with: (i) host size, (ii) snail species richness, and (iii) the distance between populations. Differences in parasite species richness are likely to play an important, yet underestimated role in the biology of this model species of vertebrate ecology and evolution

Transport through an impurity tunnel coupled to a Si/SiGe quantum dot

Achieving controllable coupling of dopants in silicon is crucial for operating donor-based qubit devices, but it is difficult because of the small size of donor-bound electron wavefunctions. Here we report the characterization of a quantum dot coupled to a localized electronic state, and we present evidence of controllable coupling between the quantum dot and the localized state. A set of measurements of transport through this device enable the determination of the most likely location of the localized state, consistent with an electronically active impurity in the quantum well near the edge of the quantum dot. The experiments we report are consistent with a gate-voltage controllable tunnel coupling, which is an important building block for hybrid donor and gate-defined quantum dot devices.Comment: 5 pages, 3 figure

Polar motion and UT1: Comparison of VLBI, lunar laser, satellite laser, satellite Doppler, and conventional astrometric determinations

Very long baseline interferometry observations made with a 3900 km baseline interferometer (Haystack Observatory in Massachusetts to Owens Valley Observation in California) were used to estimate changes in the X-component of the position of the Earth's pole and in UT1. These estimates are compared with corresponding ones from lunar laser ranging, satellite laser ranging, satellite Doppler, and stellar observations

The N- or C-terminal domains of DSH-2 can activate the C. elegans Wnt/β-catenin asymmetry pathway

AbstractDishevelleds are modular proteins that lie at the crossroads of divergent Wnt signaling pathways. The DIX domain of dishevelleds modulates a β-catenin destruction complex, and thereby mediates cell fate decisions through differential activation of Tcf transcription factors. The DEP domain of dishevelleds mediates planar polarity of cells within a sheet through regulation of actin modulators. In Caenorhabditis elegans asymmetric cell fate decisions are regulated by asymmetric localization of signaling components in a pathway termed the Wnt/β-catenin asymmetry pathway. Which domain(s) of Disheveled regulate this pathway is unknown. We show that C. elegans embryos from dsh-2(or302) mutant mothers fail to successfully undergo morphogenesis, but transgenes containing either the DIX or the DEP domain of DSH-2 are sufficient to rescue the mutant phenotype. Embryos lacking zygotic function of SYS-1/β-catenin, WRM-1/β-catenin, or POP-1/Tcf show defects similar to dsh-2 mutants, including a loss of asymmetry in some cell fate decisions. Removal of two dishevelleds (dsh-2 and mig-5) leads to a global loss of POP-1 asymmetry, which can be rescued by addition of transgenes containing either the DIX or DEP domain of DSH-2. These results indicate that either the DIX or DEP domain of DSH-2 is capable of activating the Wnt/β-catenin asymmetry pathway and regulating anterior–posterior fate decisions required for proper morphogenesis