MMLUP: Multi-Source & Multi-Task Learning for User Profiles in Social Network

With the rapid development of the mobile Internet, users generate massive data in different forms in social network every day, and different characteristics of users are reflected by these social media data. How to integrate multiple heterogeneous information and establish user profiles from multiple perspectives plays an important role in providing personalized services, marketing, and recommendation systems. In this paper, we propose Multi-source & Multi-task Learning for User Profiles in Social Network which integrates multiple social data sources and contains a multi-task learning framework to simultaneously predict various attributes of a user. Firstly, we design their own feature extraction models for multiple heterogeneous data sources. Secondly, we design a shared layer to fuse multiple heterogeneous data sources as general shared representation for multi-task learning. Thirdly, we design each task’s own unique presentation layer for discriminant output of specific-task. Finally, we design a weighted loss function to improve the learning efficiency and prediction accuracy of each task. Our experimental results on more than 5000 Sina Weibo users demonstrate that our approach outperforms state-of-the-art baselines for inferring gender, age and region of social media users.     

Obtaining minimum-correlation Latin Hypercube Sampling plans using an IP-based heuristic

The objective of Latin Hypercube Sampling is to determine an effective procedure for sampling from a (possibly correlated) multivariate population to estimate the distribution function (or at least a significant number of moments) of a complicated function of its variables. The typical application involves a computer-based model in which it is largely impossible to find a way (closed form or numerical) to do the necessary transformation of variables and where it is expensive to run in terms of computing resources and time. Classical approaches to hypercube sampling have used sophisticated stratified sampling techniques; but such sampling may provide incorrect measures of the output parameters' variances or covariances due to correlation between the sampling pairs. In this work, we offer a strategy which provides a sampling specification minimizing the sum of the absolute values of the pairwise differences between the true and sampled correlation pairs. We show that optimal plans can be obtained for even small sample sizes. We consider the characteristics of permutation matrices which minimize the sum of correlations between column pairs and then present an effective heuristic for solution. This heuristic generally finds plans which match the correlation structure exactly. When it does not, we provide a hybrid lagrangian/heuristic method, which empirically has found the optimal solution for all cases tested.This article was processed by the author using the LAT_EX style filepljour2 from Springer-Verlag.     

基于小动物荧光成像研究生物材料体内降解的实验方法

可降解材料作为生物材料的重要组成部分,其体内降解性能的好坏往往决定着材料植入后的成败。因此,对材料体内降解的评价显得尤为重要。传统的生物材料体内降解评价方法需要在各取样点取出不同批次的降解样品,阻止了对同一个实验样品降解过程的连续测量,并且存在样品需求量大的问题。小动物活体成像系统(in vivo imaging system,IVIS)具有非侵入性、操作性强等特点,为解决上述问题提供了思路。本研究旨在建立一种利用小动物荧光成像系统检测可降解材料降解性能的方法,通过将近红外荧光染料经化学反应标记到可降解材料上,由荧光强度的变化反应材料的降解程度。体内降解实验表明此方法制得的荧光标记材料,荧光稳定性高,材料降解过程中荧光强度变化与质量损失拟合效果良好(R2=0.9994)。综上,该方法解决了测量材料降解样品量大的问题,并且提高了实验过程的连贯性。      

宽带取样示波器时基误差补偿的新方法研究

时基误差严重影响宽带取样示波器的高精准测量,但对时基误差进行精确估计和补偿极为困难。针对宽带取样示波器的时基误差(含时基失真与抖动引起的误差),首次运用正交距离回归算法对宽带取样示波器时基误差进行估计。对比多相位、多频率最小二乘法,该方法仅用一组近似正交的正弦信号对宽带取样示波器的时基误差进行有效估计,实现了对测量信号的时基补偿,得出了低于0.3ps的时基误差,显著提高了宽带取样示波器测量准确度。     

What is Discussed about COVID-19: A Multi-Modal Framework for Analyzing Microblogs from Sina Weibo without Human Labeling

Starting from late 2019, the new coronavirus disease (COVID-19) has become a global crisis. With the development of online social media, people prefer to express their opinions and discuss the latest news online. We have witnessed the positive influence of online social media, which helped citizens and governments track the development of this pandemic in time. It is necessary to apply artificial intelligence (AI) techniques to online social media and automatically discover and track public opinions posted online. In this paper, we take Sina Weibo, the most widely used online social media in China, for analysis and experiments. We collect multi-modal microblogs about COVID-19 from 2020/1/1 to 2020/3/31 with a web crawler, including texts and images posted by users. In order to effectively discover what is being discussed about COVID-19 without human labeling, we propose a unified multi-modal framework, including an unsupervised short-text topic model to discover and track bursty topics, and a selfsupervised model to learn image features so that we can retrieve related images about COVID-19. Experimental results have shown the effectiveness and superiority of the proposed models, and also have shown the considerable application prospects for analyzing and tracking public opinions about COVID-19.     

计数法测量采集速率的不确定度评价

介绍了用标准周期计数法评价线性测量系统采集速率时，测量结果的不确定度分析和评价过程；讨论了影响评价结果不确定度的几个主要来源；给出了减小采集速率评价不确定度的主要措施，通过一组实例，给出了采集速率不确定度分析和评价结果，该过程及结论可应用在对于计量标准进行相应指标的不确定度分析上，也可用于估计采集速率指标本身的不确定度。     

采集速率评价结果的不确定度

目的　介绍了用标准周期计数法评价线性测量系统采集速率时测量结果的不确定度分析和评价过程 ;讨论了影响评价结果不确定的几个主要误差来源 ,包括输入信号频率、采集序列长度、采集序列中所含信号周期个数 .方法　给出了减小采集速率评价不确定度的主要措施 .结果　在一组采集速率实际评价例子上 ,给出其不确定度分析和评价结果 .结论该过程及结论可用于对计量标准进行相应指标的不确定度分析上 ,也可用于估计采集速率指标本身的不确定度     

Power and sample size calculation for 2×2 tables under multinomial sampling with random loss

Multinomial sampling, in which the total number of sampled subjects is fixed, is probably one of the most commonly used samplig schemes in categorical data analysis. When we apply multinomial sampling to collect subjects who are subject to a random exclusion from our data analysis, the number of subjects falling into each comparison group is random and can be small with a positive probability. Thus, the application of the traditional statistics derived from large sample theory for testing equality between two independent proportions can sometimes be theoretically invalid. On the other hand, using fisher's exact test can always assure that the true type I error is less than or equal to a nominal α-level. Thus, we discuss here power and sample size calculation based on this exact test. For a desired power at a given α-level, we develop an exact sample size calculation procedure, that accounts for a random loss of sampled subjects, for testing equality between two independent proportions under multinomial sampling. Because the exact sample size calculation procedure requires intensive computations when the underlying required sample size is large, we also present an approximate sample size formula using large sample theory. On the basis of Monte Carlo simulation, we note that the power of using this approximate sample size formula generally agrees well with the desired power on the basis of the exact test. Finally, we propose a trial-and-error procedure using the approximate sample size as an initial estimate and Monte Carlo simulation to expedite the procedure for searching the minimum required sample size.     

采样序列长度及周波数对正弦参数拟合的影响

针对波形拟合法估计正弦参数时,测量条件对拟合参数带来的误差影响,进行了拟合误差界的搜索研究。选取的条件变量分别是A/D位数、幅度、序列所含波形的周波数、初始相位、直流分量以及序列数据点数。以两两联动的双条件组合方式进行误差界搜索,获得了幅度、频率、相位、直流分量、动态有效位数等拟合参数的误差界随不同条件变化而变化的曲线规律,筛分出了显著影响量和不显著影响量。并对A/D位数、序列所含波形的周波数、以及序列数据点数带来的影响进行了深入研究,获得了拟合参数的误差界呈现量子化阶梯特征的显著规律,并获得了量子化阶梯边界点估计的经验公式。该结果可用于拟合正弦参数的误差评价和不确定度估计,也可以用于在设定拟合误差和不确定度情况下,选择测量条件。     

A simplified approach for real-time detection of arterial wall velocity and distension

Arterial stiffness is known to increase with age and with many vascular diseases, but its noninvasive assessment in patients still represents a difficult task. The measurement of diameter change during the cardiac cycle (distension) has been proposed as a means to estimate arterial compliance and stiffness. Therefore, we have developed a simple PC-based device and algorithm for noninvasive quantification of vessel wall motion and diameter change in humans. This goal is achieved in real-time by processing the base-band signals from a commercial ultrasound Doppler system. Real-time operation is of crucial importance, because it allows a rapid achievement of optimal measurement conditions. The system was evaluated in a laboratory using a string phantom and was tested on the carotid arteries of 10 volunteers. Wall velocities from 0.05 to 600 mm/s and displacements lower than 2 μm were detected with phantoms. The measured carotid diameter change in the volunteers ranged from 7.5 to 11.8% (mean=9.8%) and agrees closely with values reported in the literature. The difference between values taken one hour apart ranged from 0.2 to 0.5%. We conclude that the new system provides rapid, accurate, and repeatable measurements of vessel distension in humans     

Local Particle Mean Velocity Measurement in Pneumatic Conveying Pipelines Using Electrostatic Sensor Arrays

In this paper, a measurement system for the local mean velocity of pneumatically conveyed particles is proposed and developed. It mainly consists of electrostatic sensor arrays, signal conditioning circuits, and a digital signal processor (DSP)-based data acquisition and processing unit. Electrostatic sensor arrays are used to detect the charge on particles in its sensing zone and further make the local particle mean velocity measurement in conjunction with cross-correlation method. The sampling frequency is determined from theoretical analysis of the bandwidth of electrostatic signal and accuracy of correlation velocity calculation. Experiments are carried out on a belt conveyor and a gravity-fed particle rig to determine the optimized sampling number of the electrostatic signal through analyzing the measurement error of the transit time. The results showed that the more sampling numbers, the higher stability of measurement results. The repeatability of the measurement system is less than ±2.2% and the linearity is better than ±4.9% over the velocity range of 5.50–21.98 m/s. Experiments are also performed on a high-pressure dense-phase pneumatic conveying system of pulverized coal, indicating that the measurement system is capable of achieving local mean velocity measurement of pneumatically conveyed particles with the relative standard deviation less than 5.5%.     

Extended Kalman filter for estimating aircraft orientation from velocity measurements

A coordinated flight model for estimating the orientation of an aircraft under track from velocity measurements into an extended Kalman filter (EKF) framework is placed here. In doing so, it makes two contributions. First, the EKF provides a rigorous framework for addressing this problem, blending modelling error and measurement error. Second, the EKF supplements the estimated orientation with a measure of the uncertainty in that estimate. Such estimates of uncertainty are crucial in a number of applications, including using the orientation estimates to approximate the radar cross section of the aircraft under track, in an attempt to identify targets. The EKF's performance is demonstrated using both a straight-and-level manoeuvre and a complicated manoeuvre recorded on-board a manoeuvring F-15. In both cases, the state estimates of the EKF are similar to the results obtained from a coordinated flight model. The true orientations almost always fall within one standard deviation of the estimates, as determined by the estimated covariance.     

Raman mapping of low-content active-ingredient pharmaceutical formulations. part II: statistically optimized sampling for detection of less than 1% of an active pharmaceutical ingredient

Several tablets are prepared with two forms of an active pharmaceutical ingredient (API) of which one (less than 1% w/w) is considered undesirable. The presence of this component is tested for by Raman microscopy in a series of mapping experiments. These experiments are conducted with a statistically based sampling routine in which the number of spectra to collect across the whole surface of a tablet is set so as to theoretically ensure spectral detection of the low-concentration form. Such experiments are then repeated a number of times to achieve approximately 95% confidence that the strictly limited number of sampling points suffice to detect the low-concentration form and that Raman microscopy is technically a reliable method for analytical analysis of this type.     

The Measurement of Little g: A Fertile Ground for Precision Measurement Science

The occasion of the 100th anniversary of Einstein’s “golden year” provides a wonderful opportunity to discuss some aspects of gravity—gravitation being an interest of Einstein’s that occurred a few years after 1905. I’ll do this by talking about the measurement of little g, the free-fall acceleration on the Earth’s surface that is mainly due to the Earth’s gravity but whose value is also affected by centrifugal forces that are a result of the Earth’s rotation. I will also describe two equivalence experiments and a test of the inverse-square law of gravitation. Finally, I will make some observations on the science of precision measurement—a subject that underpins much of scientific progress.     

Exploring social media usage in improving public perception on workplace violence against healthcare workers

Workplace violence against healthcare workers has been a major social problem in many countries. A misunderstanding between patients and physicians is the primary cause of violence . The recent rise of social media offered a new communication channel between the government and the public. This study aims to explore and examine the use of social media to improve public perception about the medical workplace violence by considering a recently issued policy in China. We collected 12,250 posts before, during and after the implementation of the policy from Weibo, which is similar to Twitter. Sentiment classification and topic clustering methods were used to analyze the data. One-way ANOVA was applied to assess the changes of public sentiments over time. Results showed that the proportion of posts with negative sentiment statistically significantly decreased after the release of the policy, indicating the effectiveness of social media in improving public perception about the medical workplace violence, to a large extent. Topic clustering results regarding the policy showed that most people supported the policy. However, some believe that punishment measures contained in the policy need to be strengthened and that more attention should be paid to the hospitals and medical staffs, as well as how to effectively protect the interests of patients. Based on these findings, we suggested government to effectively and scientifically use social media to address medical workplace violence from the perspective of the public and further consider its causes in terms of both patients and medical staffs, and building an expert witness system seems to be helpful. Measures for guaranteeing the safety of medical staffs should be built by comprehensively evaluating the potential risk. These results can help governments increase the engagement of their citizens.     

测量条件对A/D动态有效位数评价的影响

针对正弦拟合法评价A/D动态有效位数时测量条件对动态有效位数评价带来的误差影响,进行了拟合误差界的搜索研究.选取的条件变量分别是A/D位数、幅度、序列所含波形的周波数、初始相位、直流分量以及序列数据点数.以两两联动的双条件组合方式进行误差界搜索,获得了动态有效位数评价的误差界随不同条件变化而变化的曲线规律,筛分出了显著...     

Numerical reconstruction of optical surfaces

There are several problems in optics that involve the reconstruction of surfaces such as wavefronts, reflectors, and lenses. The reconstruction problem often leads to a system of first-order differential equations for the unknown surface. We compare several numerical methods for integrating differential equations of this kind. One class of methods involves a direct integration. It is shown that such a technique often fails in practice. We thus consider one method that provides an approximate direct integration; we show that it is always converging and that it provides a stable, accurate solution even in the presence of measurement noise. In addition, we consider a number of methods that are based on converting the original equation into a minimization problem.     

Intrinsic limitations of Shack-Hartmann wavefront sensing on an extended laser guide source

In this paper we investigate the behavior of various centroiding methods (weighted center of gravity, matched filtering, and correlation) classically used in Shack-Hartmann wavefront sensing when dealing with an elongated asymmetric spot. We study the impact of model errors on these centroiding methods at high signal-to-noise ratios, and, using a one-dimensional formalism, we show that the associated estimates all suffer from a bias uncorrelated with the actual spot displacement if its shape is not known precisely. Additionally, we show that the correlation method provides an estimate with a unitary gain whatever the parameters used, while the other two methods introduce a non-unitary gain in the estimation process. Finally, we show that the sampling of the spot structures after filtering by some convolution kernels is crucial to get an unbiased estimate of the spot displacement.     

Novel Calibration Technique for a Coulometric Evolved Vapor Analyzer for Measuring Water Content of Materials

Evolved vapor coulometry is a measurement technique that selectively detects water and is used to measure water content of materials. The basis of the measurement is the quantitative electrolysis of evaporated water entrained in a carrier gas stream. Although this measurement has a fundamental principle—based on Faraday’s law which directly relates electrolysis current to amount of substance electrolyzed—in practice it requires calibration. Commonly, reference materials of known water content are used, but the variety of these is limited, and they are not always available for suitable values, materials, with SI traceability, or with well-characterized uncertainty. In this paper, we report development of an alternative calibration approach using as a reference the water content of humid gas of defined dew point traceable to the SI via national humidity standards. The increased information available through this new type of calibration reveals a variation of the instrument performance across its range not visible using the conventional approach. The significance of this is discussed along with details of the calibration technique, example results, and an uncertainty evaluation.     

Beamwidth effects on sea ice draft measurements from U.K. submarines

Single-beam upward-looking sonars mounted on British submarines have provided a vast amount of Arctic sea ice thickness data since the early 1970s. In this paper we develop a systematic procedure to estimate the bias introduced in the measurement of the ice draft by the standard procedure of taking only the first arrival of the returned echo. Because the magnitude of this error varies significantly with the depth of the submarine, the beamwidth of the sonar and the topography of the underside of the ice, it has to be calculated for each individual transect. Based on data collected during a submarine cruise in the Arctic Ocean in the winter of 2004, we estimate that for conic beams of semi-angles 3° and 6° the observed drafts are typically 7-20% and 15-35% higher than the real drafts. In view of the size of these errors, much higher than previously reported, we argue that beamwidth corrections must always be taken into account when measuring sea ice draft from below.