Evaluation of four probability distribution models for speckle in clinical cardiac ultrasound images

Segmenting cardiac ultrasound images requires a model for the statistics of speckle in the images. Although the statistics of speckle are well understood for the raw transducer signal, the statistics of speckle in the image are not. This paper evaluates simple empirical models for first-order statistics for the distribution of gray levels in speckle. The models are created by analyzing over 100 images obtained from commercial ultrasound machines in clinical settings. The data in the images suggests a unimodal scalable family of distributions as a plausible model. Four families of distributions (Gamma, Weibull, Normal, and Log-normal) are compared with the data using goodness-of-fit and misclassification tests. Attention is devoted to the analysis of artifacts in images and to the choice of goodness-of-fit and misclassification tests. The distribution of parameters of one of the models is investigated and priors for the distribution are suggested.     

基于体验学习的“过程控制”实验教学设计

"过程控制"是自动化专业的主要专业课程之一,具有专业性和实践性较强的特点。课程不仅涉及许多控制理论知识,而且与工业生产实际紧密联系。实验环节在整个课程中起着十分重要的作用。本文从体验学习理论出发,从知识获取过程的角度对过程控制实验教学环节进行了重新设计和安排,使实验教学过程更符合人获取知识过程的规律。     

浅谈COM及其创建

ＣＯＭ即组件对象模型,是一种将单个应用程序分隔成多个独立的部分,也即组件。在今天是无所不在的,并可预计将占主导地位。本文简介了ＣＯＭ的实质,和用ＶｉｓｕａｌＣ＋＋来实现ＣＯＭ。     

远程火箭末敏弹弹道特性仿真

为研究远程火箭末敏弹弹道特性,应用弹道理论和控制理论,建立了远程火箭末敏弹母弹弹道方程;引入多体系统动力学理论,分析了末敏弹系统伞、伞盘、弹等刚体间的力学关系,考虑了系统的连接方式和约束,分析了伞绳弹性,建立了末敏弹在减速运动和稳态扫描段的完整运动模型.编制了远程火箭末敏弹弹道仿真软件,进行了末敏弹全弹道数字仿真,并得到了部分试验验证,分析了末敏弹弹道特性.为远程火箭末敏弹射击精度仿真和减少精度试验用弹量奠定了基础.     

Interdisciplinary study on popularity prediction of social classified hot online events in China

We offer an interdisciplinary study of computer science and social science, analyzing behavior surrounding three types of online events: political events, social events, and non-public events. Based on the intrinsic characteristics of the three event types, this paper creates an effective method to predict such events. We continuously followed and recorded data every 10 min for 10 months from September 14, 2012 to July 11, 2013, and collected over 14 million “hot” posts from Sina Weibo, the largest microblogging provider in China. After removing spammers and noises, we developed a database of 4180 hot online events and 7,761,395 threads. We found that people’s online behavior regarding event types varies in terms of follow-up statistics and the predictability of events. The Chinese are, typically, quite concerned with social affairs that relate most closely to their personal interests and preferences. People tend to cluster around political events more often than social events and non-public events. This is demonstrated by an algorithm embedded with a clustering growth pattern of events, which predicts the popularity of online political events above others. The statistical findings are justified by Habermas’ public sphere theory and the theory of vertical/horizontal collectivism/individualism. This research provides an interesting piece of computational social science work to assist in the analysis of incentives concerning China’s collective events.     

Minimizing Average Schedule Length under Memory Constraints by Optimal Partitioning and Prefetching

Over the last 20 years, the performance gap between CPU and memory has been steadily increasing. As a result, a variety of techniques has been devised to hide that performance gap, from intermediate fast memories (caches) to various prefetching and memory management techniques for manipulating the data present in these caches. In this paper we propose a new memory management technique that takes advantage of access pattern information that is available at compile time by prefetching certain data elements before explicitly being requested by the CPU, as well as maintaining certain data in the local memory over a number of iterations. In order to better take advantage of the locality of reference present in loop structures, our technique also uses a new approach to memory by partitioning it and reducing execution to each partition, so that information is reused at much smaller time intervals than if execution followed the usual pattern. These combined approaches—using a new set of memory instructions as well as partitioning the memory—lead to improvements in total execution time of approximately 25% over existing methods.     

以可靠性为中心的引导计算机结构设计

引导计算机是引导系统的核心。为了提高引导系统的安全可靠性,采用非相似余度技术,从而避免共性故障带来的严重后果。从安全的实际需求出发,对引导计算机的体系结构进行研究,设计了一种基于非相似余度的引导计算机结构方案,并应用一种简化的可靠性结构模型对其进行可靠性分析,结果显示该结构能满足系统的安全可靠性指标。     

5G的信号波形

本文介绍了5G采用的多载波波形,包括正交频分多路复用(OFDM),滤波器组多载波(FBMC),通用滤波器多载波(UFMC)和广义频分复用(GFDM),说明其基本原理和优缺点,以及在增强移动宽带(e MMB)、海量机器型通信(m MTC)和超可靠低时延(URLLC)通信中的应用。     

Tracking myocardial motion from cine DENSE images using spatiotemporal phase unwrapping and temporal fitting

Displacement encoding with stimulated echoes (DENSE) encodes myocardial tissue displacement into the phase of the MR image. Cine DENSE allows for rapid quantification of myocardial displacement at multiple cardiac phases through the majority of the cardiac cycle. For practical sensitivities to motion, relatively high displacement encoding frequencies are used and phase wrapping typically occurs. In order to obtain absolute measures of displacement, a two-dimensional (2-D) quality-guided phase unwrapping algorithm was adapted to unwrap both spatially and temporally. Both a fully automated algorithm and a faster semi-automated algorithm are proposed. A method for computing the 2-D trajectories of discrete points in the myocardium as they move through the cardiac cycle is introduced. The error in individual displacement measurements is reduced by fitting a time series to sequential displacement measurements along each trajectory. This improvement is in turn reflected in strain maps, which are derived directly from the trajectories. These methods were validated both in vivo and on a rotating phantom. Further measurements were made to optimize the displacement encoding frequency and to estimate the baseline strain noise both on the phantom and in vivo. The fully automated phase unwrapping algorithm was successful for 767 out of 800 images (95.9%), and the semi-automated algorithm was successful for 786 out of 800 images (98.3%). The accuracy of the tracking algorithm for typical cardiac displacements on a rotating phantom is 0.24 +/- 0.15 mm. The optimal displacement encoding frequency is in the region of 0.1 cycles/mm, and, for 2 scans of 17-s duration, the strain noise after temporal fitting was estimated to be 2.5 +/- 3.0% at end-diastole, 3.1 +/- 3.1% at end-systole, and 5.3 +/- 5.0% in mid-diastole. The improvement in intra-myocardial strain measurements due to temporal fitting is apparent in strain histograms, and also in identifying regions of dysfunctional myocardium in studies of patients with infarcts.