DESIGN OF A POLARIZATION-INDEPENDENT MMI SOI COUPLER BASED MICRORESONATOR USING SANDWICH STRUCTURES

A microresonator based on multimode interference (MMI) couplers using sandwich structures is described in this paper. The birefringence can be controlled by introducing an additional dielectric layer within a silicon channel waveguide. It is shown that a polarization-independent MMI coupler based ring resonator can be achieved by choosing appropriate structure parameters

New Approach to Mach-Zehnder Interferometer (MZI) Cell Based on Silicon Waveguides for Nanophotonic Circuits

In this chapter, we present a new scheme for Mach-Zehnder Interferometer (MZI) structure based on only one 4 × 4 multimode interference (MMI) coupler. We design the new MZI cell on the silicon on insulator (SOI) platform. The MZI based on directional coupler and 2 × 2 MMI coupler is also investigated in detail. The new MZI cell is a basic building block for photonic applications such as optical quantum gate, optical computing and reconfigurable processors. The numerical simulations show that our approach has advantages of compact size, ease of fabrication with the current complementary metal oxide semiconductor (CMOS) circuitry

Corruption, Provincial Institutions and Capital Structure: New Evidence From a Transitional Economy

Using a unique firm-provincial level panel dataset from 2005 to 2011, this study for the first time investigates the role played by corruption and provincial institutions in determining a company’s capital structure in Vietnam’s legal environment. Contrasting to the majority of previous studies, the results show that corruption has an insignificant influence on a company’s bank loans, consistent with institutional theory. However, the role of corruption is different for types of various capital structures after controlling for both unobservable characteristics and endogeneity problems. More specifically, corruption has significantly positive influence on short-term capital structure, but a negative impact on long-term loans. All of these results hold after a series of robust tests. &nbsp

University Students' Perceptions of Native and Non-Native English-Speaking Teachers in Pre-Sessional Courses in Vietnam

Research Articl

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

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

Multi-Response Optimization of Burnishing Variables for Minimizing Environmental Impacts

The purpose of this investigation is to optimize minimum quantity lubrication (MQL) variables, including the nozzle diameter (D), inclined angle (A), air pressure (P), oil quantity (F), and spraying distance (S) for decreasing the energy consumption in the burnishing time (EB) and particulate matter index (PI) of the interior burnishing process. The optimal adaptive neuro-based-fuzzy inference system (ANFIS) models of the performance measures were proposed in terms of the MQL variables with the aid of the Taguchi method. The non-dominated sorting genetic algorithm based on the grid partitioning (NSGA-G) and TOPSI were employed to produce feasible solutions and determine the best optimal point. The obtained results indicated that the optimal values of the D, A, P, F, and S are 1.0 mm, 35 deg., 3 Bar, 70 ml/h, and 10 mm, respectively, while the EB and PI are decreased by 8.0% and 15.7% at the optimal solution. The optimal ANFIS models were trustworthy and ensure accurate predictions. The optimization technique comprising the ANFIS, NSGA-G, and TOPSIS could be extensively utilized to determine the optimal outcomes instead of the trial-error and/or human experience. The outcomes could help to decrease environmental impacts in the practical burnishing process

Factors Affecting C02 Emission in Vietnam: a Panel Data Analysis

The purpose of this study is to investigate the major factors in the process of economic growth that influence the carbon dioxide (CO2) emission in Vietnam. An Autoregressive Distributed Lag (ARDL) model was used to evaluate the impact based on Environmental Kuznets curve (EKC) and Pollution haven hypothesis (PHH) in 1990–2011. The results indicate that the economic growth, energy consumption, financial development and trade openness  positively influence the CO2 emissions, whereas foreign direct investment has a negative impact in the short term. Coefficient of joining ASEAN is not statistically significant. The findings of this study also support the validity of EKC and PHH in the Vietnamese economy. Therefore, it is important to use green energy, examine requirements for foreign investment and adopt trade-related measures and policies to increase environmental protection

Effects of bribery on natural resource efficiency in Vietnam: moderating effects of market competition and credit constraints

This article uses small and medium-sized enterprises’ (SMEs) survey data in Vietnam from 2007 to 2015 to examine the effects of bribery on the natural resource efficiency of firms facing credit constraints and market competition. We also employ the disaggregated resource intensity by water, fuel, and electricity. Creditconstrained firms are broken down into those who have had formal loan applications denied (credit rationed) and those who do not apply for formal loans due to either the process being too difficult or the interest rate being too high (discouraged borrowers). Applying instrumental variable method to take into account the endogeneity problem, the empirical results provide evidence to support the ‘sanding-the-wheels of resource efficiency’ hypothesis. Among the three natural resources, inefficiency is most evident in water consumption. Furthermore, the effects become more sizable for micro-sized and informally registered firms since they have a lower bargaining power vis-a-vis public officials. Credit constraints and market competition pressure can reduce a firm’s ability to use natural resources efficientl

Welfare consequences of inconsistent monetary policy implementation in Vietnam

We develop a New Keynesian model featuring Calvo price setting and Calvo wage setting to quantify the welfare consequences of shifting trend inflation in Vietnam. To capture the characteristics of the Vietnamese economy, we use the Simulated Method of Moment and calibrate parameters jointly to match the important selected moments of Vietnamese data. The results show a severe consequence of a constant positive trend inflation and an exogenous shock to trend inflation, especially when a central bank sets a high level of inflation target. Among staggered price and wage contracts, the latter play a vital role in transmitting the adverse impacts of constant and shifting trend inflation into the economy. Based on our analyses, raising inflation targets would seem to be a bad policy prescription in Vietnam