Parametric amplification in single-walled carbon nanotube nanoelectromechanical resonators

The low quality factor (Q) of Single-walled carbon nanotube (SWNT) resonators has limited their sensitivity in sensing application. To this end, we employ the technique of parametric amplification by modulating the spring constant of SWNT resonators at twice the resonant frequency, and achieve 10 times Q enhancement. The highest Q obtained at room temperature is around ~700, which is 3-4 times better than previous Q record reported for doubly-clamped SWNT resonators. Furthermore, efficient parametric amplification is found to only occur in the catenary vibration regime. Our results open up the possibility to employ light-weight and high-Q carbon nanotube resonators in single molecule and atomic mass sensing.Comment: 14 pages, 3 figure

A Study of the Application of Guided Discovery Method in English Grammar Teaching in Junior High School

Grammar is an important part of language. However, in actual grammar teaching, teachers directly impart grammar rules and students passively accept them. This has led to students’ disinterest in English grammar lessons and unsatisfactory grammar learning results. In order to promote students’ grammar learning, in recent years, some experts and scholars have begun to explore the application of guided discovery method in grammar classrooms. Guided discovery method is a teaching method that emphasizes guidance and focuses on discovery. Through setting up a situation, the teacher guides students to engage in the discovery activity of grammar rules by communicating with each other.This thesis uses questionnaire survey and interviews to analyze the application of guided discovery method in junior high school English grammar classrooms, as well as to analyze the positive effects of junior high school English teachers’ use of the guided discovery method on students’ grammar learning. Based on Bruner’s Discovery Learning Theory and Piaget’s Constructivism Learning Theory, this thesis takes Nanning High-tech Industrial Development Zone Minda Middle School as an example. It was found that under the guidance of guided discovery method, students’ interest and motivation in learning grammar have improved. Also, students’ autonomous learning abilities have been enhanced. Finally, students’ grammar learning strategies were cultivated through guided discovery method. Students can summarize grammar knowledge and solve grammar problems by reasoning and inducting. However, there are a small number of students who still do not have that strong learning ability cannot understand the tasks assigned by the teacher in class, so they do not learn grammar efficiently

A rank based metric of anchor models for speaker verification

In this paper, we present an improved method of anchor models for speaker verification. Anchor model is the method that represent a speaker by his relativity of a set of other speakers, called anchor speakers. It was firstly introduced for speaker indexing in large audio database. We suggest a rank based metric for the measurement of speaker character vectors in anchor model. Different from conventional metric methods which consider each anchor speaker equally and compare the log likelihood scores directly, in our method the relative order of anchor speakers is exploited to characterize target speaker. We have taken experiments on the YOHO database. The results show that EER of our method is 13.29 % lower than that of conventional metric. Also, our method is more robust against the mismatching between test set and anchor set. 1