405,524 research outputs found
Specification Testing in Nonlinear Time Series with Long-Range Dependence
No full textThis paper proposes a model specification testing procedure for parametric specification of the conditional mean function in a nonlinear time series model with long–range dependence. An asymptotically normal test is established even when long–range dependence is involved. In order to implement the proposed test in practice using a simulated example, a bootstrap simulation procedure is established to find a simulated critical value to compute both the size and power values of the proposed test.Asymptotic theory, Gaussian process, nonlinear time series, long-range dependence, parametric specification
A power-saving modulation technique for time-of-flight range imaging sensors
No full textTime-of-flight range imaging cameras measure distance and intensity simultaneously for every pixel in an image. With the continued advancement of the technology, a wide variety of new depth sensing applications are emerging; however a number of these potential applications have stringent electrical power constraints that are difficult to meet with the current state-of-the-art systems. Sensor gain modulation contributes a significant proportion of the total image sensor power consumption, and as higher spatial resolution range image sensors operating at higher modulation frequencies (to achieve better measurement precision) are developed, this proportion is likely to increase. The authors have developed a new sensor modulation technique using resonant circuit concepts that is more power efficient than the standard mode of operation. With a proof of principle system, a 93–96% reduction in modulation drive power was demonstrated across a range of modulation frequencies from 1–11 MHz. Finally, an evaluation of the range imaging performance revealed an improvement in measurement linearity in the resonant configuration due primarily to the more sinusoidal shape of the resonant electrical waveforms, while the average precision values were comparable between the standard and resonant operating modes
Viewpoint: Range Science and Range Management are Complementary but Distinct Endeavors
No full textRange management and range science are complementary but distinct endeavors. Range management is an attempt to optimize returns from rangelands in combinations desired by and suitable for society through the manipulation of range ecosystems (Stoddart et al. 1975). As such, range management is a planning process in which alternative management options are exposed to the decision-maker\u27s values, and the option with the highest value is selected. Range science is the body of scientific knowledge upon which range management should be based. As such, range science should be the set of concepts and ideas that agree or are consistent with how natural processes operate. Both are necessary for wise use of range resources. The purpose of this paper is to discuss the roles of planning and science in range management, to provide examples of biological processes important in range management, and to discuss the role of range science in understanding those processes
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Range Unit Root (RUR) Tests: Robust against Nonlinearities, Error Distributions, Structural Breaks and Outliers
No full textSince the seminal paper by Dickey and Fuller in 1979, unit-root tests have conditioned the standard approaches to analysing time series with strong serial dependence in mean behaviour, the focus being placed on the detection of eventual unit roots in an autoregressive model fitted to the series. In this paper, we propose a completely different method to test for the type of long-wave patterns observed not only in unit-root time series but also in series following more complex data-generating mechanisms. To this end, our testing device analyses the unit-root persistence exhibited by the data while imposing very few constraints on the generating mechanism. We call our device the range unit-root (RUR) test since it is constructed from the running ranges of the series from which we derive its limit distribution. These nonparametric statistics endow the test with a number of desirable properties, the invariance to monotonic transformations of the series and the robustness to the presence of important parameter shifts. Moreover, the RUR test outperforms the power of standard unit-root tests on near-unit-root stationary time series; it is invariant with respect to the innovations distribution and asymptotically immune to noise. An extension of the RUR test, called the forward?backward range unit-root (FB-RUR) improves the check in the presence of additive outliers. Finally, we illustrate the performances of both range tests and their discrepancies with the Dickey?Fuller unit-root test on exchange rate series.Publicad
Characterization for high dynamic range imaging
No full textIn this paper we present a new practical camera characterization technique to improve color accuracy in high dynamic range (HDR) imaging. Camera characterization refers to the process of mapping device-dependent signals, such as digital camera RAW images, into a well-defined color space. This is a well-understood process for low dynamic range (LDR) imaging and is part of most digital cameras — usually mapping from the raw camera signal to the sRGB or Adobe RGB color space. This paper presents an efficient and accurate characterization method for high dynamic range imaging that extends previous methods originally designed for LDR imaging. We demonstrate that our characterization method is very accurate even in unknown illumination conditions, effectively turning a digital camera into a measurement device that measures physically accurate radiance values — both in terms of luminance and color — rivaling more expensive measurement instruments
Design of planar inverted-F antennas (PIFA) for multiband wireless applications
No full textA small three bands printed inverted-F antenna with independently controlling the resonant frequency is presented. The proposed antenna consists of two arms
supported by shorting walls fed by 50 Ω microstrip transmission line and a ground plane. The antenna occupied a compact size of 26 x 25 x 3.75 mm. The main radiated patch
injected with slot and another arm to generate and control the three resonant frequencies to cover 2.4, 3.7 and 5.2GHz
Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX). The simulated and measured results show that the antenna achieves a gain of 2, 3 and 5 dBi respectively and radiation efficiency of 50%, 60% and 85% for the three bands respectively. The simulated and measured result for the return loss is in good agreements
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Modeling long-range dependent Gaussian processes with application in continuous-time financial models
No full textThis paper considers a class of nonstationary Gaussian processes with possible long-range dependence (LRD) and intermittency. The author proposes a new estimation method to simultaneously estimate both the LRD and intermittency parameter. An application of the proposed estimation method to a continuous-time financial model is discussed.continuous-time model; diffusion process; long-range dependent process; parameter estimation; stochastic volatility
3D Shape Reconstruction from Multiple Range Image Views
No full textShape reconstruction of different three dimensional objects using multiple range images has evolved recently within the recent past. In this research shape reconstruction of a three dimensional object using multiple range image views is investigated.
Range images were captured using the Waikato Range Imager. This range images camera is novel in that it uses heterodyne imaging and is capable of acquiring range images with precision less than a millimeter simultaneously over a full field. Multiple views of small objects were taken and the FastRBF was explored as a mean of registration and surface rendering. For comparison to the real range data, simulated range data under noise free condition were also generated and reconstructed with the FastRBF tool box.
The registration and reconstruction of simple object was performed using different views with the FastRBF toolbox. Analysis of the registration process showed that the translation error produced due to distortion during registration of different views hinders the process of reconstructing a complete surface. While analyzing the shape reconstruction using the FastRBF tool it is also determined that a small change in accuracy values can affect the interpolation drastically. Results of reconstruction of a real 3D object from multiple views are shown
- …
