A Local-Global LDA Model for Discovering Geographical Topics from Social Media

Micro-blogging services can track users' geo-locations when users check-in their places or use geo-tagging which implicitly reveals locations. This "geo tracking" can help to find topics triggered by some events in certain regions. However, discovering such topics is very challenging because of the large amount of noisy messages (e.g. daily conversations). This paper proposes a method to model geographical topics, which can filter out irrelevant words by different weights in the local and global contexts. Our method is based on the Latent Dirichlet Allocation (LDA) model but each word is generated from either a local or a global topic distribution by its generation probabilities. We evaluated our model with data collected from Weibo, which is currently the most popular micro-blogging service for Chinese. The evaluation results demonstrate that our method outperforms other baseline methods in several metrics such as model perplexity, two kinds of entropies and KL-divergence of discovered topics

Limited Heredity Diversity of the Critically Endangered Guizhou Golden Monkeys

Guizhou golden monkey (Rhinopithecus brelichi) was a unique, endangered and endemic primate species in Guizhou Province. It was an isolated population caused by habitat loss and fragmentation due to the human disturbance in the recently 30 years in China, only distributed in Fanjingshan National Natural Reserve, Guizhou Province. To know the background with demonic population structure, we sequenced 867 bp of the mitochondrial DNA D-loop from 312 fresh fecal samples, results showed there 11 haplotypes among these samples, h was 0.517, π was 0.00413. It indicated that this species had the lowest genetic diversity among four golden monkeys in China and need strengthen the conversation concern for this species immediately

Thompson Sampling for Combinatorial Semi-Bandits

We study the application of the Thompson sampling (TS) methodology to the stochastic combinatorial multi-armed bandit (CMAB) framework. We analyze the standard TS algorithm for the general CMAB, and obtain the first distribution-dependent regret bound of $O(mK_{\max}\log T / \Delta_{\min})$, where $m$ is the number of arms, $K_{\max}$ is the size of the largest super arm, $T$ is the time horizon, and $\Delta_{\min}$ is the minimum gap between the expected reward of the optimal solution and any non-optimal solution. We also show that one cannot directly replace the exact offline oracle with an approximation oracle in TS algorithm for even the classical MAB problem. Then we expand the analysis to two special cases: the linear reward case and the matroid bandit case. When the reward function is linear, the regret of the TS algorithm achieves a better bound $O(m\sqrt{K_{\max}}\log T / \Delta_{\min})$. For matroid bandit, we could remove the independence assumption across arms and achieve a regret upper bound that matches the lower bound for the matroid case. Finally, we use some experiments to show the comparison between regrets of TS and other existing algorithms like CUCB and ESCB

Effects of laser fluence on silicon modification by four-beam laser interference

This paper discusses the effects of laser fluence on silicon modification by four-beam laser interference. In this work, four-beam laser interference was used to pattern single crystal silicon wafers for the fabrication of surface structures, and the number of laser pulses was applied to the process in air. By controlling the parameters of laser irradiation, different shapes of silicon structures were fabricated. The results were obtained with the single laser fluence of 354 mJ/cm, 495 mJ/cm, and 637 mJ/cm, the pulse repetition rate of 10 Hz, the laser exposure pulses of 30, 100, and 300, the laser wavelength of 1064 nm, and the pulse duration of 7-9 ns. The effects of the heat transfer and the radiation of laser interference plasma on silicon wafer surfaces were investigated. The equations of heat flow and radiation effects of laser plasma of interfering patterns in a four-beam laser interference distribution were proposed to describe their impacts on silicon wafer surfaces. The experimental results have shown that the laser fluence has to be properly selected for the fabrication of well-defined surface structures in a four-beam laser interference process. Laser interference patterns can directly fabricate different shape structures for their corresponding applications

Characterization of Ba\u3csub\u3e1-x-y\u3c/sub\u3eCa\u3csub\u3ex\u3c/sub\u3eSr\u3csub\u3ey\u3c/sub\u3eTiO\u3csub\u3e3\u3c/sub\u3e Perovskites as Pb-Free Dielectric Materials

Use of lead-containing piezoelectric components in electrical and electronic devices has been banned on the EU market since July 1st, 2006. Development of lead-free high performance piezoelectric materials to meet the strong market demand is therefore imperative. In this paper, we report a systematic study on the structural, dielectric and ferroelectric properties of one class of lead-free piezoelectric materials, Ba1-x-yCaxSryTiO3 (x = 0-0.4, and y = 0-0.2) ceramics, using techniques such as XRD, SEM, impedance analyzer, and ferroelectric analyzer. It is found that with increasing Sr concentration in Ba1-ySryTiO3 and Ba0.8-ySryCa0.2TiO3, the crystal structure transforms from tetragonal to cubic along with a decreased unit-cell volume. The microstructures of all samples prepared are uniform and dense with the grain size decreasing with Sr content. The Curie temperature decreases faster with Sr and Ca co-doped BaTiO3 than that of Sr or Ca singularly-doped one. Above Curie temperature, a tunability of 31.4% can be achieved at an applied voltage of 30 kV/cm for (Ba0.6Ca0.2Sr0.2TiO3). These properties promise Ba1-x-yCaxSryTiO3 system to be applicable in Pb-free tunable devices

A COMPARATIVE STUDY OF GRADES 8 AND 9 STUDENTS’ BELIEFS TOWARDS TASK-BASED APPROACH AND TEACHER-CENTERED APPROACH IN TEACHING CHINESE AS A FOREIGN LANGUAGE CLASS AT A PRIVATE SCHOOL IN BANGKOK, THAILAND

The purpose of this study was to investigate the levels of Grades 8 and 9 students’ beliefs as well as determine whether there was significant differences between task-based approach and teacher-centered approach in teaching Chinese as a foreign language class at a private school in Bangkok, Thailand. There were 92 Grade 8 and 90 Grade 9 participants as a population sample in the 2020-2021 academic year in this study. This research was designed as a quantitative comparative study. The students’ beliefs towards teaching approaches questionnaire from Zhang and Liu (2014) was used as the research instrument in this study. Descriptive statistic was utilized to analyze the levels of Grade 8 and Grade 9 students’ beliefs towards task-based approach and teacher-centered approach in teaching Chinese as a foreign language (CFL) class. Dependent samples t-test was used to compare whether there were significant differences between task-based approach and teacher-centered approach in teaching CFL class. The findings revealed that Grades 8 and 9 students expressed their positive beliefs towards task-based approach in teaching CFL class but showed their neutral belief towards teacher-centered approach. There was a significant difference in Grade 8 and Grade 9 students’ beliefs towards task-based and teacher-centered approaches in teaching CFL class. According to these findings, researcher provided some recommendations for students, Chinese teachers, school administrators, and future researchers