Multimode Waveguides on an SOI Platform for Arbitrary Power Splitting Ratio Couplers

Optical power couplers with arbitrary power splitting ratios are important components for many applications such as Mach-Zehnder interferometer-based structures, filters, switches, dispersion compensations, optical interconnects, and microring resonators. In this chapter, we present a new approach to achieve a very high compact coupler with arbitrary power splitting ratios on silicon on insulator (SOI) waveguides. The proposed device requires only one 4×4 multimode interference (MMI) coupler. We use a passive wide SOI waveguide to achieve the phase shifter. The footprint of the whole device is only about 6×150 μm2. A large fabrication tolerance of ±50 nm can be achieved. The modified effective index method, beam propagation method, finite difference method, and finite difference-time difference method are used to optimally design the whole device

Travel Intention and Travel Behaviour in the Post-Pandemic Era: Evidence from Vietnam

Tourism is on the pathway of returning and contributes to the economic development of many countries. Understanding the decision-making process of tourism customers in the post-pandemic context is crucial for a strong recovery of the tourism sector. The paper aims to identify the determinants of travel intention and the link between travel intention and travel behaviour in the post-COVID-19 pandemic period. A total number of 431 questionnaires regarding the individual behaviour of Vietnamese travellers were collected. The empirical results reveal that electronic word of mouth, crisis management, and destination image in COVID have positive relationships with travel intention. Besides, travel intention is positively linked with the customers’ travel behaviour during the post-pandemic era. By contrast, the results do not support the conclusion regarding the relationship between risk communication, the healthcare system, non-pharmaceutical interventions and the travel intention of customers. Finally, the practical implications are included for enhancing a faster recovery process of the tourism sector

High FSR and Critical Coupling Control of Microring Resonator Based on Graphene-Silicon Multimode Waveguides

We present a new approach for designing a compact microring resonator structure based on only one multimode waveguide, which can provide a very high free spectral range (FSR) and capability of controlling the critical coupling. The silicon on insulator (SOI) waveguide and graphene-silicon waveguide (GSW) are used for the proposed structure. By changing the applied voltage on the graphene sheet, we can achieve a full control of the critical coupling. Some important properties of the proposed microring resonator such as free spectral range and quality factor are analyzed. We show that our structure can provide all characteristics of a single microring resonator with universal applications such as optical switching, modulating, filtering and signal processing, etc

TinyQMIX: Distributed Access Control for mMTC via Multi-agent Reinforcement Learning

Distributed access control is a crucial component for massive machine type communication (mMTC). In this communication scenario, centralized resource allocation is not scalable because resource configurations have to be sent frequently from the base station to a massive number of devices. We investigate distributed reinforcement learning for resource selection without relying on centralized control. Another important feature of mMTC is the sporadic and dynamic change of traffic. Existing studies on distributed access control assume that traffic load is static or they are able to gradually adapt to the dynamic traffic. We minimize the adaptation period by training TinyQMIX, which is a lightweight multi-agent deep reinforcement learning model, to learn a distributed wireless resource selection policy under various traffic patterns before deployment. Therefore, the trained agents are able to quickly adapt to dynamic traffic and provide low access delay. Numerical results are presented to support our claims.Comment: 6 pages, 4 figures, presented at VTC Fall 202

Multifactorial Evolutionary Algorithm For Clustered Minimum Routing Cost Problem

Minimum Routing Cost Clustered Tree Problem (CluMRCT) is applied in various fields in both theory and application. Because the CluMRCT is NP-Hard, the approximate approaches are suitable to find the solution for this problem. Recently, Multifactorial Evolutionary Algorithm (MFEA) has emerged as one of the most efficient approximation algorithms to deal with many different kinds of problems. Therefore, this paper studies to apply MFEA for solving CluMRCT problems. In the proposed MFEA, we focus on crossover and mutation operators which create a valid solution of CluMRCT problem in two levels: first level constructs spanning trees for graphs in clusters while the second level builds a spanning tree for connecting among clusters. To reduce the consuming resources, we will also introduce a new method of calculating the cost of CluMRCT solution. The proposed algorithm is experimented on numerous types of datasets. The experimental results demonstrate the effectiveness of the proposed algorithm, partially on large instance

An efficient approach to measure the difficulty degree of practical programming exercises based on student performances

oai:ojs.www.rev-jec.org:article/282This study examines the generality of easy to hard practice questions in programming subjects. One of the most important contributions is to propose four new formulas for determining the difficulty degree of questions. These formulas aim to describe different aspects of difficulty degree from the learner's perspective instead of the instructor's subjective opinions. Then, we used clustering technique to group the questions into three easy, medium and difficult degrees. The results will be the baseline to consider the generality of the exercise sets according to each topic. The proposed solution is then tested on the data set that includes the results of the two subjects: Programming Fundamentals, Data Structures and Algorithms from Ho Chi Minh City University of Technology. The most important result is to suggest the instructors complete various degrees according to each topic for better evaluating student's performance

Government’s and professional associations’ roles in promoting corporate social resposibility – An exploratory in Vietnamese construction firms

With this large number of operating company, the construction industry in Vietnam needs the direction and supports from the government and professional associations not only in policies, business strategies, information about construction but also in leading and providing CSR information and instruction. By employing qualitative approach with in-depth interview as the main method to collect data, this study is to explore actual managers’ perspectives of the current roles of these two stakeholders in CSR and their expectations for the upcoming years. Two worthy notes need to be concerned. The first note is that the roles of government are really important in issuing appropriate policies and treating businesses fairly. Another note relating that of professional associations points out that construction firms do not have any belief in their operations

Influences of social ties on firms’ performance - A study in Vietnam on corporate social responsibility practices

Social ties and their influences on firm’s performance are still issues of many debates. The reason is that previous studies gave different findings about the effects of social ties on firm’s performance. This study, therefore, focuses on finding what managers in construction firms perceive of social ties in their business and how these ties affect corporate social responsibility (CSR) practices – an aspect of firm’s performance. To address these research objectives, qualitative approach is employed and in-depth interview with managers in construction firms is conducted to collect the data. Furthermore, the study also explores how managers think of CSR changes in the near future. The research findings show that interviewees strongly believe in CSR changes including both internal and external changes. In terms of social ties, the research also identifies government authorities and professional associations; and business partners as political and business ties, respectively. The findings show that managers easily realize business ties and their effects on CSR practices. Meanwhile, only some managers with years of seniority can perceive of political ties and their effects. The research findings also suggest some noteworthy issues for the authorities of the industry to consider including lack of information among managers about firm’s aspects and relationships, and the significance of professional associations (a type of political ties) although these ties currently have no influences on CSR practices of construction businesses