High-Accuracy Confidence Regions for Distribution Parameters

With the help of today’s computers, it is always relatively easy to find maximum-likelihood estimators of one or more parameters of any specific statistical distribution, and use these to construct the corresponding approximate confidence interval/region, facilitated by the well-known asymptotic properties of the likelihood function. The purpose of this article is to make this approximation substantially more accurate by extending the Taylor expansion of the corresponding probability density function to include quadratic and cubic terms in several centralized sample means, and thus finding the corresponding -proportional correction to the original algorithm. We then demonstrate the new procedure’s usage, both for constructing confidence regions and for testing hypotheses, emphasizing that incorporating this correction carries minimal computational and programming cost. In our final chapter, we present two examples to indicate how significantly the new approximation improves the procedure’s accuracy.

High-accuracy self-mixing interferometer based on multiple reflections using a simple external reflecting mirror

A self-mixing interferometer(SMI)with resolution twenty times higher than that of a conventional interferometer is developed by multiple reflections.Only by employing a simple external reflecting mirror,the multiple-pass optical configuration can be constructed.The advantage of the configuration is simple and easy to make the light re-injected back into the laser cavity.Theoretical analysis shows that the resolution of measurement is scalable by adjusting the number of reflections.The experiment shows that the proposed method has the optical resolution of approximateλ/40.The influence of displacement sensitivity gain(G)is further analyzed and discussed in practical experiments.

A unified intrinsic functional expansion theory for solitary waves

A new theory is developed here for evaluating solitary waves on water, with results of high accuracy uniformly valid for waves of all heights, from the highest wave with a corner crest of 120 down to very low ones of diminishing height. Solutions are sought for the Euler model by employing a unified expansion of the logarithmic hodograph in terms of a set of intrinsic component functions analytically determined to represent all the intrinsic properties of the wave entity from the wave crest to its outskirts. The unknown coefficients in the expansion are determined by minimization of the mean-square error of the solution, with the minimization optimized so as to take as few terms as needed to attain results as high in accuracy as attainable. In this regard, Stokess formula, F2= tan , relating the wave speed (the Froude number F) and the logarithmic decrement of its wave field in the outskirt, is generalized to establish a new criterion requiring (for minimizing solution error) the functional expansion to contain a finite power series in M terms of Stokess basic term (singular in ), such that 2M is just somewhat beyond unity, i.e. 2M1. This fundamental criterion is fully validated by solutions for waves of various amplitude-to-water depth ratio =a/h, especially about 0.01, at which M=10 by the criterion. In this pursuit, the class of dwarf solitary waves, defined for waves with 0.01, is discovered as a group of problems more challenging than even the highest wave. For the highest wave, a new solution is determined here to give the maximum height hst=0.8331990, and speed Fhst=1.290890, accurate to the last significant figure, which seems to be a new record.

Calibration chain design based on integrating sphere transfer radiometer for SI-traceable on-orbit spectral radiometric calibration and its uncertainty analysis

In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors,a transfer chain consisting of a fiber coupling monochromator（FBM） and an integrating sphere transfer radiometer（ISTR） was designed in this paper.Depending on the Sun,this chain based on detectors provides precise spectral radiometric calibration and measurement to spectrometers in the reflective solar band（RSB） covering 300–2500 nm with a spectral bandwidth of 0.5–6 nm.It shortens the traditional chain based on lamp source and reduces the calibration uncertainty from 5% to 0.5% by using the cryogenic radiometer in space as a radiometric benchmark and trap detectors as secondary standard.This paper also gives a detailed uncertainty budget with reasonable distribution of each impact factor,including the weak spectral signal measurement with uncertainty of 0.28%.According to the peculiar design and comprehensive uncertainty analysis,it illustrates that the spectral radiance measurement uncertainty of the ISTR system can reach to 0.48%.The result satisfies the requirements of SI-traceable on-orbit calibration and has wider significance for expanding the application of the remote sensing data with high-quality.

Methods for the construction of DEMs of artificial slopes considering morphological features and semantic information

As human activities increase,artificially modified terrain is increasingly widely distributed in road,hydrological,and urban construction.Artificially modified terrain plays an important role in protecting from geological disasters and in the planning and design of urban landscapes.Compared with natural slopes,artificial slopes have obvious morphological characteristics.Traditional modeling methods are no longer suitable for digital elevation model(DEM)modeling of artificial slopes because they often seriously distort the DEM results.In this paper,from the perspective of morphological characteristics,artificial slopes are divided into two types,namely,regular slopes and irregular slopes,based on whether the top and bottom lines of the artificial slope are parallel.Then,according to the morphological characteristics of the two types of slopes,the following DEM construction methods are designed:the first method(perpendicular+inverse distance weighted)is suitable for regular slopes,and the second method(perpendicular+high-accuracy surface modeling)is suitable for irregular slopes.Finally,a DEM construction test is carried out using the artificial slopes in the study area.The results show that for the regular and irregular slopes in the study area,the construction method proposed in this paper has significant advantages in morphological accuracy over the traditional method(triangulated irregular network),and the elevation accuracy method is also superior to the traditional method(using this method,the mean error and standard deviation error of the regular slope DEM are 0.08 m and 0.13 m,respectively,and those of the irregular slope DEM are 0.08 m and 0.06 m).In addition,the top lines and bottom lines can be included in the DEM construction of the background area after processing the elevation information of the boundary line to realize a smooth transition in the boundary between the artificial slope and the background area.

光滑粒子流体力学方法在流体、固体和生物力学中的应用

光滑粒子流体动力学(smoothed particle hydrodynamics,SPH)作为最早发展的无网格粒子方法之一,对于模拟爆炸、冲击等涉及大变形问题,具有广阔的发展前景.本文对SPH方法在流体、固体和生物力学领域的改进算法和工程应用进行了全面介绍.阐述了SPH的基本理论和高精度SPH改进算法,分析了流体、固体和生物力学领域的改进技术.在模拟流体问题时,采用δ-SPH和GSPH方法解决了流体不稳定性的问题,并且讨论了流固耦合中的界面接触方法.针对固体的数值模拟,总结了三种传统改进方法(如应力点法、守恒光滑法、人工应力法)和Total Lagrangian SPH方法,改善了拉伸不稳定性问题;在生物力学方面,阐述了SPH控制方程和相互作用力的计算方法.本文综述了近年来SPH方法的应用进展,包括复杂海洋工程中的流固耦合问题,固体领域的天体、岩土力学、爆炸冲击以及增材制造等工程应用和生物力学中血流动力学、肠道健康和植物生长等典型应用;并分析了国内外SPH软件的发展,介绍了多尺度自适应分辨率方法、并行计算方法和网格自动生成技术来克服数值模拟方法在计算效率和计算规模上的限制.最后对目前存在的问题进行总结与展望,包括提高SPH算法的数值精度、如何精确描述固体的损伤与断裂问题和计算精度与效率之间的平衡等.在未来研究中,建立多尺度耦合SPH模型和深度学习将是进一步拓宽SPH方法应用的重要方向.

A 13-bit, 8 MSample/s pipeline A/D converter

A 13-bit 8 MSample/s high-accuracy CMOS pipeline ADC is proposed. At the input, the sample-andhold amplifier （SHA） is removed for low power and low noise; meanwhile, an improved sampling circuit is adopted to alleviate the clock skew effect. On-chip bias current is programmable to achieve low power dissipation at different sampling rates. Particularly, drain-to-source voltages in the operational amplifiers （opamps） are fixed to ensure high DC gain within the variant range of the bias current. Both on-chip and off-chip decoupling capacitors are used in the voltage reference circuit in consideration of low power and stability. The proposed ADC was implemented in 0.18-μm 1P6M CMOS technology. With a 2.4-MHz input, the measured peak SNDR and SFDR are 74.4 and 91.6 dB at 2.5 MSample/s, 74.3 and 85.4 dB at 8.0 MSample/s. It consumes 8.1, 21.6, 29.7, and 56.7 mW （including I/O drivers） when operating at 1.5, 2.5, 5.0, and 8.0 MSample/s with 2.7 V power supply, respectively. The chip occupies 3.2 mm^2, including I/O pads.

Skeleton Marching-based Parallel Vascular Geometry Reconstruction Using Implicit Functions

Fast high-precision patient-specific vascular tissue and geometric structure reconstruction is an essential task for vascular tissue engineering and computer-aided minimally invasive vascular disease diagnosis and surgery.In this paper,we present an effective vascular geometry reconstruction technique by representing a highly complicated geometric structure of a vascular system as an implicit function.By implicit geometric modelling,we are able to reduce the complexity and level of difficulty of this geometric reconstruction task and turn it into a parallel process of reconstructing a set of simple short tubular-like vascular sections,thanks to the easy-blending nature of implicit geometries on combining implicitly modelled geometric forms.The basic idea behind our technique is to consider this extremely difficult task as a process of team exploration of an unknown environment like a cave.Based on this idea,we developed a parallel vascular modelling technique,called Skeleton Marching,for fast vascular geometric reconstruction.With the proposed technique,we first extract the vascular skeleton system from a given volumetric medical image.A set of sub-regions of a volumetric image containing a vascular segment is then identified by marching along the extracted skeleton tree.A localised segmentation method is then applied to each of these sub-image blocks to extract a point cloud from the surface of the short simple blood vessel segment contained in the image block.These small point clouds are then fitted with a set of implicit surfaces in a parallel manner.A high-precision geometric vascular tree is then reconstructed by blending together these simple tubular-shaped implicit surfaces using the shape-preserving blending operations.Experimental results show the time required for reconstructing a vascular system can be greatly reduced by the proposed parallel technique.