The Weight Distributions of Cyclic Codes and Elliptic Curves

Cyclic codes with two zeros and their dual codes as a practically and theoretically interesting class of linear codes, have been studied for many years. However, the weight distributions of cyclic codes are difficult to determine. From elliptic curves, this paper determines the weight distributions of dual codes of cyclic codes with two zeros for a few more cases

A study on mutual information-based feature selection for text categorization

Feature selection plays an important role in text categorization. Automatic feature selection methods such as document frequency thresholding (DF), information gain (IG), mutual information (MI), and so on are commonly applied in text categorization. Many existing experiments show IG is one of the most effective methods, by contrast, MI has been demonstrated to have relatively poor performance. According to one existing MI method, the mutual information of a category c and a term t can be negative, which is in conflict with the definition of MI derived from information theory where it is always non-negative. We show that the form of MI used in TC is not derived correctly from information theory. There are two different MI based feature selection criteria which are referred to as MI in the TC literature. Actually, one of them should correctly be termed "pointwise mutual information" (PMI). In this paper, we clarify the terminological confusion surrounding the notion of "mutual information" in TC, and detail an MI method derived correctly from information theory. Experiments with the Reuters-21578 collection and OHSUMED collection show that the corrected MI method’s performance is similar to that of IG, and it is considerably better than PMI

Detection of Pedestrians and Helmets in Large Construction Site

It is necessary for workers to wear helmets when working in large construction sites. The traditional way to supervise the workers whether wearing helmets or not for safety is artificial, which have brought out many problems such as many blind spots, labor and time costing. Since a large number of surveillance cameras are currently installed in these construction sites, the surveillance video can be developed in taking the place of human supervision in an intelligent way. This paper designs a pedestrian and helmet detection network based on Faster R-CNN. In feature extraction, we have chosen the Residual Network (Resnet) combined with the Feature Pyramid Network (FPN) because the objects have small size, low resolution and less semantic information in whole scenes. We have also designed a parallel residual Block (PRB) combined with the Receptive Field Block (RFB) to strength feature extraction. The feature maps obtained from different convolution layers have been fused twice. And we have studied two fusion methods. Experiment results from our own dataset show that our proposed detection network improves the mAP by 8.74% and 2.3% respectively compared with Yolov3 and Faster R-CNN, at the cost of 0.3 FPS slower than Faster R-CNN

Mathematical Modeling and Analysis of Drill String Longitudinal Vibration with Lateral Inertia Effect

Comparative analysis whether considering the lateral inertia or not, aiming at the longitudinal vibration of the drill string in drilling progress, is proposed. In the light of the actual condition, the mechanical model of the drill string about vibration is established on the basis of the theoretical analysis. Longitudinal vibration equation of the drill string is derived from the Rayleigh-Love model and one-dimensional viscoelastic model. According to the Laplace transform method and the relationships among parameters of the model, the solutions to complex impedance at the bottom of the drill string are obtained, and then the comparison results are analyzed, which is the lateral inertia effect on longitudinal vibration characteristics. The researches show that the smaller the length of the drill string, the greater the cross-sectional area of the drill string, the greater the damping coefficient of bottom hole on the bottom of the drill string, and the more evident the effect on the dynamic stiffness of the drill string with lateral inertia effect. The Poisson ratio of the drill string only has some effects on it taking account of the lateral inertia effect, and the influence is relatively small compared with the former three conditions