Prediction of propeller hydromechanics for a single-shafter

Object and purpose of research. This paper discusses hydromechanics properties of propeller and their scaling laws. The purpose of this study was to analyse existing methods of scaling model test data through their comparison with full-scale test results, identify possible sources of considerable error that might be present in them, as well as update the method of model test data scaling taking into account hydrodmechanic interaction between propeller and hull in terms of their model data extrapolation to the full scale. Materials and methods. The paper discusses general relationships between hydromechanic parameters of hull and propeller, that arise, in their turn, from the fundamental laws of mechanics. These relationships were used to analyse interconnected laws governing the full-scale extrapolation of model test data for hull resistance, propeller thrust and propeller torque. Main results. The study identified some incorrect hypotheses in current scaling methods for hydrodynamics of propeller in behind-hull conditions, that might bring about considerable error in full-scale estimates of operational advance coefficient, thrust coefficient, efficiency and RPM. Conclusion. This paper suggests alternative techniques for determination of operational advance coefficient and other hydromechanics parameters of full-scale propeller, so as to obtain the estimates that take into account physical peculiarities of scale effect and also correlate with the results of full-scale trials.

Production of two Nasal Sounds by Speakers with Cleft Palate

Many speakers with cleft palate develop atypical consonant productions, especially for pressure consonants such as plosives, fricatives, and affricates. The present study investigated the nature of nasal sound errors. The participants were eight female and three male speakers with cleft palate between the ages of 6 to 20. Speakers were audio-recorded, and midsagittal tongue movement was captured with ultrasound. The speakers repeated vowel-consonant-vowel with the vowels /α/, /i/, and /u/ and the alveolar and velar nasal consonants /n/ and /η/. The productions were reviewed by three listeners. The participants showed a variety of different placement errors and insertions of plosives, as well as liquid productions. There was considerable error variability between and within speakers, often related to the different vowel contexts. Three speakers co-produced click sounds. The study demonstrated the wide variety of sound errors that some speakers with cleft palate may demonstrate for nasal sounds. Nasal sounds, ideally in different vowel contexts, should be included in articulation screenings for speakers with cleft palate, perhaps more than is currently the case.

Accuracy of the box-counting algorithm for noisy fractals

The box-counting (BC) algorithm is applied to calculate fractal dimensions of four fractal sets. The sets are contaminated with an additive noise with amplitude [Formula: see text]. The accuracy of calculated numerical values of the fractal dimensions is analyzed as a function of [Formula: see text] for different sizes of the data sample. In particular, it has been found that even in case of pure fractals ([Formula: see text]) as well as for tiny noise ([Formula: see text]) one has considerable error for the calculated exponents of order 0.01. For larger noise the error is growing up to 0.1 and more, with natural saturation limited by the embedding dimension. This prohibits the power-like scaling of the error. Moreover, the noise effect cannot be cured by taking larger data samples.

Income Perception, Information, and Progressive Taxation: Evidence from a Survey Experiment

Are individuals accurately informed about their place in the income distribution? Despite the importance of accurate information about one’s placement in the income distribution for many models of redistribution, this assumption remains untested. We present survey data and an embedded experiment where we inform some individuals their true place in the income distribution. We then assess the impact of such information on tax progressivity preferences. We find that individuals have considerable error regarding their self-placement in the income distribution. Revealing to individuals their true placement affects progressivity preferences for individuals who learn they are poor, and for individuals whose prior is that they are poor. These results have implications for information assumptions of redistribution models of comparative political economy and contribute to our understanding of tax preferences, an understudied dimension of redistribution preferences.

An Improved Evaluation Method of Routing Strategy

The main purpose of designing an evaluation method for routing strategy is to accurately evaluate the performance of a series of routing strategies at various network loads, including under-load, full- load and even overload. Most researchers evaluate the effectiveness of a new routing strategy with the method of OrderParameter. However in this evaluating process, we find that its result distributes in a certain range of values instead of a single value, soOrderParameterintroduces a considerable error, it is difficult to evaluate the performance of a routing strategy accurately in different network load with it. To solve this problem, a method--ImprovedOrderParameter (OOP)is proposed. This method can not only get a fixed critical value for a special network load, but also depict the transition of network load over time. According to simulation experiment, theOOPcan be more objective to evaluate the performance of a routing strategy at various network load.

Research of Aviation Image Multiplication Based on the Fractal Interpolation Algorithm

The resolution of aerial images was low, because the aviation aerospace camera was far from the scenery when shooting. In order to see the object of the aviation images clearly,the aviation images should be enlarged to improve the resolution . As the complexity and irregularity of the aerial images, the texture features is lost and considerable error is caused by using the traditional methods. In this article, the fractal interpolation has been used to enlarge the images, which can not only overcome the shortcoming of the linear interpolation, but also maintain the fine texture features of the original images, which is helpful to obtain higher accuracy than the traditional interpolation.

Effect of Inertia Variation Due to Reciprocating Parts and Connecting Rod on Coupled Free Vibration of Crankshaft

The inertia due to reciprocating parts and connecting rods, as felt by the crankshaft, varies with the crank angle. The effect of inertia variation on torsional free vibration of crankshafts has been studied extensively. In this paper, the effect on combined torsional and bending free vibrations is examined. Single-cylinder engine crankshaft geometry is considered for the study. The results indicate that the inertial coupling, introduced by the reciprocating parts and connecting rod, significantly influences the free vibration characteristics, particularly when the natural frequencies of the crankskahft are closely spaced. The results suggest that, under such conditions, modeling the crankshaft as a pure torsional system would involve considerable error.

The Present State of Psychiatric Epidemiology

The seven uses of epidemiology identified by Morris all have direct relevance for mental disorders. But psychiatric epidemiology has a number of distinguishing features: it has to depend on a nosology that may lack validity; it depends largely on subjective symptoms for its data; the morbidity it deals with is really a continuum, and not a dichotomy of cases and unaffected persons; the measurement of morbidity using scales or standardised interviews is open to considerable error; and the unbiased assessment of environmental exposures proves to be technically challenging. Some of these features have been the basis of interesting research developments. The main milestones in the progress of psychiatric epidemiology are reviewed, together with some of the current issues of general interest, including activities in Australasia.

Nanomechanical Response of Materials and Thin Film Systems: Finite Element Simulation

Finite element simulation of the nanoindentation process has been carried out to investigate the nanomechanical response of materials and thin film systems. The influence of the geometry of the indenter, friction between the indenter and the surface, and pre-stress in the film, on the nanomechanical response have all been investigated. The effect of pile-up on the contact area calculation and the problems which occur with the commonly used methods in calculating the contact area have been studied. Results shows considerable error in calculating the contact area which depends on the indentation conditions used for the simulation. Simulation results suggest, that the influence of residual stress on hardness response is material sensitive.

Are probability estimates from the permutation model of Mantel's test stable?

Matrix comparison tests (i.e., Mantel's test or quadratic assignment) are employed with increasing frequency to measure the concordance between genetic, behavioural, morphological, ecological, and geographic distances. Such tests compare an observed measure of matrix association with a null distribution derived from a randomly generated subset of all possible permutations of one of the original matrices. Typically, 500–2000 randomly permutated matrices are used to generate the statistical distribution and thereby estimate the probability of obtaining an observed association between two matrices. We demonstrate that a considerable error (i.e., 5–6%) may be associated with probability estimates based on such low numbers of permutations. To ensure the stability of the probability estimates (i.e., increase the reliability of the test), we recommend the use of a minimum of 10 000 permutations, and 100 000 permutations if the observed probability approaches a critical significance value (e.g., 0.05).