title: Closed-form inverses for the mixed pixel/multipath interference problem in AMCW lidar

authors: Godbaz, John Peter

subjects: mixed pixels

abstract: We present two new closed-form methods for mixed pixel/multipath interference separation in AMCW lidar systems. The mixed pixel/multipath interference problem arises from the violation of a standard range-imaging assumption that each pixel integrates over only a single, discrete backscattering source. While a numerical inversion method has previously been proposed, no close-form inverses have previously been posited. The first new method models reflectivity as a Cauchy distribution over range and uses four measurements at different modulation frequencies to determine the amplitude, phase and reflectivity distribution of up to two component returns within each pixel. The second new method uses attenuation ratios to determine the amplitude and phase of up to two component returns within each pixel. The methods are tested on both simulated and real data and shown to produce a significant improvement in overall error. While this paper focusses on the AMCW mixed pixel/multipath interference problem, the algorithms contained herein have applicability to the reconstruction of a sparse one dimensional signal from an extremely limited number of discrete samples of its Fourier transform.

text: Closed-form inverses for the mixed pixel/multipath interference problem in AMCW lidar We present two new closed-form methods for mixed pixel/multipath interference separation in AMCW lidar systems. The mixed pixel/multipath interference problem arises from the violation of a standard range-imaging assumption that each pixel integrates over only a single, discrete backscattering source. While a numerical inversion method has previously been proposed, no close-form inverses have previously been posited. The first new method models reflectivity as a Cauchy distribution over range and uses four measurements at different modulation frequencies to determine the amplitude, phase and reflectivity distribution of up to two component returns within each pixel. The second new method uses attenuation ratios to determine the amplitude and phase of up to two component returns within each pixel. The methods are tested on both simulated and real data and shown to produce a significant improvement in overall error. While this paper focusses on the AMCW mixed pixel/multipath interference problem, the algorithms contained herein have applicability to the reconstruction of a sparse one dimensional signal from an extremely limited number of discrete samples of its Fourier transform.

year: 2012

title: Adaptive prediction interval for data stream regression

authors: Sun, Yibin

subjects: computer science

abstract: Prediction Interval (PI) is a powerful technique for quantifying the uncertainty of regression tasks. However, research on PI for data streams has not received much attention. Moreover, traditional PI-generating approaches are not directly applicable due to the dynamic and evolving nature of data streams. This paper presents AdaPI (ADAptive Prediction Interval), a novel method that can automatically adjust the interval width by an appropriate amount according to historical information to converge the coverage to a user-defined percentage. AdaPI can be applied to any streaming PI technique as a postprocessing step. This paper develops an incremental variant of the pervasive Mean and Variance Estimation (MVE) method for use with AdaPI. An empirical evaluation over a set of standard streaming regression tasks demonstrates AdaPI’s ability to generate compact prediction intervals with a coverage close to the desired level, outperforming alternative methods.

text: Adaptive prediction interval for data stream regression Prediction Interval (PI) is a powerful technique for quantifying the uncertainty of regression tasks. However, research on PI for data streams has not received much attention. Moreover, traditional PI-generating approaches are not directly applicable due to the dynamic and evolving nature of data streams. This paper presents AdaPI (ADAptive Prediction Interval), a novel method that can automatically adjust the interval width by an appropriate amount according to historical information to converge the coverage to a user-defined percentage. AdaPI can be applied to any streaming PI technique as a postprocessing step. This paper develops an incremental variant of the pervasive Mean and Variance Estimation (MVE) method for use with AdaPI. An empirical evaluation over a set of standard streaming regression tasks demonstrates AdaPI’s ability to generate compact prediction intervals with a coverage close to the desired level, outperforming alternative methods.

year: 2024

title: Wearing moko: Maori facial marking in today’s world

authors: Nikora, Linda Waimarie

subjects: moko

abstract: The early voyagers, missionaries, settlers all reacted to the pukanohi, to the marked faces of the Maori people, during the period of first contact, and the century following it. Their accounts are vivid, judgemental, revealing, telling us as much about them as they do about the people they described.
Curiosity and horror are mixed with a genuine
fascination; where sternly evangelizing words
failed, armed confrontation occurred; and we
now live with the results, te ao hou, a new world. In this world, today, wahine mau kauae, tangata mau moko, pukanohi – wearers – are speaking for themselves, about themselves, and commenting on how others view them. Unanimously, they insist that the decision to take the marking is about continuity, affirmation, identity and commitment. It is also about wearing those ancestors, carrying them into the future; as their moko become a companion, a salient being with its own life force, its own integrity and power, beyond the face.

text: Wearing moko: Maori facial marking in today’s world The early voyagers, missionaries, settlers all reacted to the pukanohi, to the marked faces of the Maori people, during the period of first contact, and the century following it. Their accounts are vivid, judgemental, revealing, telling us as much about them as they do about the people they described.
Curiosity and horror are mixed with a genuine
fascination; where sternly evangelizing words
failed, armed confrontation occurred; and we
now live with the results, te ao hou, a new world. In this world, today, wahine mau kauae, tangata mau moko, pukanohi – wearers – are speaking for themselves, about themselves, and commenting on how others view them. Unanimously, they insist that the decision to take the marking is about continuity, affirmation, identity and commitment. It is also about wearing those ancestors, carrying them into the future; as their moko become a companion, a salient being with its own life force, its own integrity and power, beyond the face.

year: 2004-04-04