Using the revised EM algorithm to remove noisy data for improving the one-against-the-rest method in binary text classification

Automatic text classification is the problem of automatically assigning predefined categories to free text documents, thus allowing for less manual labors required by traditional classification methods. When we apply binary classification to multi-class classification for text classification, we usually use the one-against-the-rest method. In this method, if a document belongs to a particular category, the document is regarded as a positive example of that category; otherwise, the document is regarded as a negative example. Finally, each category has a positive data set and a negative data set. But, this one-against-the-rest method has a problem. That is, the documents of a negative data set are not labeled manually, while those of a positive set are labeled by human. Therefore, the negative data set probably includes a lot of noisy data. In this paper, we propose that the sliding window technique and the revised EM (Expectation Maximization) algorithm are applied to binary text classification for solving this problem. As a result, we can improve binary text classification through extracting potentially noisy documents from the negative data set using the sliding window technique and removing actually noisy documents using the revised EM algorithm. The results of our experiments showed that our method achieved better performance than the original one-against-the-rest method in all the data sets and all the classifiers used in the experiments.     

基于Monte Carlo模拟的软土基坑隆起风险评估研究

基于圆弧滑动模型确定的安全系数,将基坑隆起破坏的不利事件划分为5种情况,利用Monte Carlo模拟确定不利事件发生概率,提出了考虑基坑隆起破坏引起的不利事件发生概率及经济损失的风险评估模型。将所提方法应用于福州地铁2号线某基坑工程中,结果表明,当围护结构插入比小于1.2时,加固对基坑隆起破坏损失期望减小效果显著;当围护结构插入比大于1.2时,加固对基坑隆起破坏损失期望减小效果一般;当插入比小于0.8时,基坑隆起破坏的损失期望等级属于“严重”;当插入比介于0.8～1.2时,基坑隆起破坏的损失期望等级属于“需要考虑”;当插入比大于1.2时,基坑隆起破坏的损失期望等级属于“可忽略”。     

组织人力资本配置过程的内耗机理及测度研究

本文重点论述了组织中人力资本内耗的机理及其数学描述和量化测度。在组织中,个体既相互协作,又相互内耗,因而,人力资本总量因合作而提升,因内耗而降低。在分析内耗机理的基础上,给出了计算人力资本内耗值的原理和方法,及减少内耗的有效途径。     

基于并行滑动窗口算法的RSA计时攻击防御的研究

模幂运算是RSA公钥密码算法中最基本也是最耗时的运算。为了防御计时攻击,一般采用以"绑定法"为代表,影响运算性能的模幂算法。本文指出并行滑动窗口算法在不牺牲性能的条件下,对于RSA计时攻击有内在的免疫能力,并在特定条件下可以有效提高RSA密码算法的运算速度,具有推广的价值。     

Determining friction and effective loading for sled sprinting

Understanding the impact of friction in sled sprinting allows the quantification of kinetic outputs and the effective loading experienced by the athlete. This study assessed changes in the coefficient of friction (µ_k) of a sled sprint-training device with changing mass and speed to provide a means of quantifying effective loading for athletes. A common sled equipped with a load cell was towed across an athletics track using a motorised winch under variable sled mass (33.1–99.6 kg) with constant speeds (0.1 and 0.3 m · s^?1), and with constant sled mass (55.6 kg) and varying speeds (0.1–6.0 m · s^?1). Mean force data were analysed, with five trials performed for each condition to assess the reliability of measures. Variables were determined as reliable (ICC > 0.99, CV < 4.3%), with normal-force/friction-force and speed/coefficient of friction relationships well fitted with linear (R² = 0.994–0.995) and quadratic regressions (R² = 0.999), respectively (P < 0.001). The linearity of composite friction values determined at two speeds, and the range in values from the quadratic fit (µ_k = 0.35–0.47) suggested µ_k and effective loading were dependent on instantaneous speed on athletics track surfaces. This research provides a proof-of-concept for the assessment of friction characteristics during sled towing, with a practical example of its application in determining effective loading and sled-sprinting kinetics. The results clarify effects of friction during sled sprinting and improve the accuracy of loading applications in practice and transparency of reporting in research.     

基于迭代滑模的船舶动力定位非线性控制

针对存在外界干扰的船舶动力定位控制问题,提出一种简捷的迭代滑模控制算法。选择迭代滑模面,并将其与反步法结合,设计迭代滑模控制律。采用Lyapunov理论对系统的稳定性进行证明。将提出的控制算法与PID控制算法和传统反步滑模控制算法进行理论分析比较和仿真结果比较,结果表明迭代滑模控制算法具有超调小,收敛速度快,稳定性和鲁棒性好的优点。     

关于滚动物体所受静摩擦力的方向问题的教学

判断作纯滚动的刚体所受静摩擦力的方向,只要假设此刻刚体不受到静摩擦力的作用,那么刚体上的触点相对于接触面运动的加速度的反方向,即为静摩擦力的方向.对于刚体作"既滚且滑"的运动,此时触点与接触面之间的相对速度不为零,因此,刚体受到的是滑动摩擦力,我们只须考虑触点相对于接触面的速度,好可判断摩擦力的方向.     

基于实践的高中物理摩擦力教学研究

物理是一门实用学科,在生活中处处有体现.教师要将课堂知识与生活常识相结合,以培养学生的物理思维,使学生巩固相关物理知识.文章以高中物理课本中的摩擦力教学为例,对生活中的摩擦力进行分析,并从实践的角度提出摩擦力教学的相关策略.     

云南某水电站厂房边坡破坏机理模拟研究

滑坡的破坏模式和破坏机理是滑坡防治的重要依据,并对所采取的防治措施具有重要的指导意义.本文利用FLAC3D模拟了云南某水电站厂房边坡在施工开挖作用下的破坏模式和破坏的机理,通过模拟滑坡的位移变化特征以及分布规律,指出该水电站厂房边坡在施工开挖卸荷作用下并不是一个单纯的滑坡现象,也不是一个单纯的崩塌现象,而是一个以滑为主,局部产生崩塌的松散崩滑体.     

内耗技术在金属晶体原子缺陷方面的应用研究

通过内耗技术在金属晶体原子缺陷方面的应用研究,阐述了因晶体中原子缺陷的存在而导致温度谱上产生内耗峰．Snoek峰和Zener峰是两个典型的由原子缺陷引起的弛豫峰,晶体中原子缺陷含量和结构的不同会引起内耗峰的特征不同,从而可利用内耗峰的特征和参数来探测原子缺陷的结构甚至含量．