3,195 research outputs found

    A deterministic algorithm for experimental design applied to tomographic and microseismic monitoring surveys

    Get PDF
    SUMMARY Most general experimental design algorithms are either: (i) stochastic and hence give different designs each time they are run with finite computing power, or (ii) deterministic but converge to results that depend on an initial or reference design, taking little or no account of the range of all other possible designs. In this paper we introduce an approximation to standard measures of experimental design quality that enables a new algorithm to be used. The algorithm is simple, deterministic and the resulting experimental design is influenced by the full range of possible designs, thus addressing problems (i) and (ii) above. Although the designs produced are not guaranteed to be globally optimal, they significantly increase the magnitude of small eigenvalues in the model–data relationship (without requiring that these eigenvalues be calculated). This reduces the model uncertainties expected post-experiment. We illustrate the method on simple tomographic and microseismic location examples with varying degrees of seismic attenuation

    Time-Series Evidence of the Effect of the Minimum Wage on Youth Employment and Unemployment

    Get PDF
    While previous time series studies have quite consistently found that the minimum wage reduces teenage employment, the extent of this reduction is much less certain. Moreover, because few previous studies report results of more than one specification, the causes of differences in estimated impacts are not well understood. Less consensus is evident on the effect of the minimum wage on teenage unemployment, or its relative impact on black and white teenagers. The purpose of this paper is both to update earlier work and to analyze the sensitivity of estimated minimum wage effects to alternative specification choices. In addition to providing estimates of the effect of minimum wage increases on aggregate employment and unemployment rates of teenagers, we explore several related issues: the relative importance of changing the level and coverage of the minimum wage; the timing of responses to a change in the minimum; effects on part-time and full-time work; effects on young adults (age 20-24).

    The Effect of the Minimum Wage on Employment and Unemployment: A Survey

    Get PDF
    In this paper, we survey theoretical models of the effect of the minimum wage and, in somewhat greater detail, evidence of its effect on employment and unemployment. Our discussion of the theory emphasizes recent work using two-sector and heterogeneous-worker models. We then summarize and evaluate the large literature on employment and unemployment effects of the minimum on teenagers. Finally, we survey the evidence of the effect of the minimum wage on adult employment, and on employment in low-wage industries and areas.

    An adaptive neuro-fuzzy propagation model for LoRaWAN

    Get PDF
    This article proposes an adaptive-network-based fuzzy inference system (ANFIS) model for accurate estimation of signal propagation using LoRaWAN. By using ANFIS, the basic knowledge of propagation is embedded into the proposed model. This reduces the training complexity of artificial neural network (ANN)-based models. Therefore, the size of the training dataset is reduced by 70% compared to an ANN model. The proposed model consists of an efficient clustering method to identify the optimum number of the fuzzy nodes to avoid overfitting, and a hybrid training algorithm to train and optimize the ANFIS parameters. Finally, the proposed model is benchmarked with extensive practical data, where superior accuracy is achieved compared to deterministic models, and better generalization is attained compared to ANN models. The proposed model outperforms the nondeterministic models in terms of accuracy, has the flexibility to account for new modeling parameters, is easier to use as it does not require a model for propagation environment, is resistant to data collection inaccuracies and uncertain environmental information, has excellent generalization capability, and features a knowledge-based implementation that alleviates the training process. This work will facilitate network planning and propagation prediction in complex scenarios

    Modeling of Wave Propagation in Inhomogeneous Media

    Get PDF

    Characterization and evaluation of the microcantilever radiation detector

    Get PDF
    In this study, a microcantilever charged-particle detector was characterized and evaluated. The method employed involved sensing an electric field emanating from a small collector plate on which charge built up to charged-particle flux.Sensitivity to alpha particles was determined using frequency and damping rate parameter shifts. Alpha particle detection experiments were compared to experiments using a charged plate of fixed voltage in order to characterize response more fully and to identify differences between expected charge accumulation and actual accumulation. Changes in cantilever behavior resulting from changes in ambient environmental conditions were also studied in order to determine to what extent they would impact charged-particle detection. In particular, microcantilever tip-surface adhesion force and jump-to-contact distance were studied as a function of relative humidity, and the dynamics of the liquid neck extending between the micro cantilever tip and the surface at small separation distances were investigated. In addition, relationship between the angle of the microcantilever tip relative to the surface and the excitation of multiple resonance modes was identified and described
    corecore