Combinatorial pulse position modulation for power-efficient free-space laser communications

A new modulation technique called combinatorial pulse position modulation (CPPM) is presented as a power-efficient alternative to quaternary pulse position modulation (QPPM) for direct-detection, free-space laser communications. The special case of 16C4PPM is compared to QPPM in terms of data throughput and bit error rate (BER) performance for similar laser power and pulse duty cycle requirements. The increased throughput from CPPM enables the use of forward error corrective (FEC) encoding for a net decrease in the amount of laser power required for a given data throughput compared to uncoded QPPM. A specific, practical case of coded CPPM is shown to reduce the amount of power required to transmit and receive a given data sequence by at least 4.7 dB. Hardware techniques for maximum likelihood detection and symbol timing recovery are presented

Combinatorial FSK modulation for power-efficient high-rate communications

Deep-space and satellite communications systems must be capable of conveying high-rate data accurately with low transmitter power, often through dispersive channels. A class of noncoherent Combinatorial Frequency Shift Keying (CFSK) modulation schemes is investigated which address these needs. The bit error rate performance of this class of modulation formats is analyzed and compared to the more traditional modulation types. Candidate modulator, demodulator, and digital signal processing (DSP) hardware structures are examined in detail. System-level issues are also discussed

Assessing Potential Errors in Level-of-Effort Paradata using GPS Data

Surveys are a critical resource for social, economic, and health research. The ability to efficiently collect these data and develop accurate post-survey adjustments depends upon reliable data about effort required to recruit sampled units. Level-of-effort paradata are data generated by interviewers during the process of collecting data in surveys. These data are often used as predictors in nonresponse adjustment models or to guide data collection efforts. However, recent research has found that these data may include measurement errors, which would lead to inaccurate decisions in the field or reduced effectiveness for adjustment purposes (Biemer, Chen, & Wang, 2013; West, 2013). In order to assess whether errors occur in level-of-effort paradata for in-person surveys, we introduce a new source of data – Global Positioning System (GPS) data generated by smartphones carried by interviewers. We examine the quality of the GPS data. We also link the GPS data with the interviewer-reported call records in order to identify potential errors in the call records. Specifically, we examine the question of whether there may be missing call records. Given the lack of a gold standard, we perform a sensitivity analysis under various assumptions to see how these would change our conclusions

Iowa recreational property ownership: Identification, contact and social dynamics of multiple-use perennial landcover

This research explored the opportunities for expanding the productive use of perennial landscapes in Iowa through expanded beef and dairy grazing owned recreational lands

Findings of Fact

To many of us rules of procedure are nebulous and for that reason we emphasize substantive rules of law even though most of us know the importance of the former. The authors hope in the following material to remove some of this cloudiness from one limited phase of procedure, that of fact finding. This article is meant to be of assistance to trial judges on whom the final responsibility for preparation of the findings rests. It is also aimed at counsel who may assist in the preparation or who may object to the findings made by the court. Lastly, students should be aware of the fact-finding process that the trial court has gone through when studying appellate court decisions. Although the basis of the material is derived from federal procedure, the advice and the suggestions should in the main be applicable to most statute proceedings. We shall attempt to illustrate (1) the purpose of the dings, (2) when they are required, (3) how they should be prepared, (4) their effect on appeal, and (5) the effect of a failure to make the necessary findings

Colloidal diffusion and hydrodynamic screening near boundaries

The hydrodynamic interactions between colloidal particles in small ensembles are measured at varying distances from a no-slip surface over a range of inter-particle separations. The diffusion tensor for motion parallel to the wall of each ensemble is calculated by analyzing thousands of particle trajectories generated by blinking holographic optical tweezers and by dynamic simulation. The Stokesian Dynamics simulations predict similar particle dynamics. By separating the dynamics into three classes of modes: self, relative and collective diffusion, we observe qualitatively different behavior depending on the relative magnitudes of the distance of the ensemble from the wall and the inter-particle separation. A simple picture of the pair-hydrodynamic interactions is developed, while many-body-hydrodynamic interactions give rise to more complicated behavior. The results demonstrate that the effect of many-body hydrodynamic interactions in the presence of a wall is much richer than the single particle behavior and that the multiple-particle behavior cannot be simply predicted by a superposition of pair interactions

Survey Costs: Where Are We and What Is the Way Forward?

Survey costs are a major driver of survey design decisions and thought to be related to survey errors. Despite their importance, no common language exists for discussing survey costs, nor are there established criteria for identifying which cost metrics are useful for which purposes. Past efforts to study survey costs may have been hampered by the notion that more reporting is better reporting. This article starts by introducing a typology for survey cost metrics defined by the type of cost (estimated, observed in records, and actually incurred), currency versus non-currency measures, and level of aggregation (total, by components, per unit, relative). We also suggest a set of criteria – errors in costs, generalizability, and the degree to which a cost measure is informative about survey error sources – for evaluating the utility of cost metrics. We illustrate the evaluative criteria with the cost metrics. We argue that clearly articulating types of survey costs and resetting these baseline evaluative criteria for the utility of different types of costs will help us expand research in this critical area. We conclude with recommendations for future research in costs within and across organizations

Genomic correlates of relationship QTL involved in fore-versus hind limb divergence in mice

Divergence of serially homologous elements of organisms is a common evolutionary pattern contributing to increased phenotypic complexity. Here, we study the genomic intervals affecting the variational independence of fore- and hind limb traits within an experimental mouse population. We use an advanced intercross of inbred mouse strains to map the loci associated with the degree of autonomy between fore- and hind limb long bone lengths (loci affecting the relationship between traits, relationship quantitative trait loci [rQTL]). These loci have been proposed to interact locally with the products of pleiotropic genes, thereby freeing the local trait from the variational constraint due to pleiotropic mutations. Using the known polymorphisms (single nucleotide polymorphisms [SNPs]) between the parental strains, we characterized and compared the genomic regions in which the rQTL, as well as their interaction partners (intQTL), reside. We find that these two classes of QTL intervals harbor different kinds of molecular variation. SNPs in rQTL intervals more frequently reside in limb-specific cis-regulatory regions than SNPs in intQTL intervals. The intQTL loci modified by the rQTL, in contrast, show the signature of protein-coding variation. This result is consistent with the widely accepted view that protein-coding mutations have broader pleiotropic effects than cis-regulatory polymorphisms. For both types of QTL intervals, the underlying candidate genes are enriched for genes involved in protein binding. This finding suggests that rQTL effects are caused by local interactions among the products of the causal genes harbored in rQTL and intQTL intervals. This is the first study to systematically document the population-level molecular variation underlying the evolution of character individuation