1. Highly Selective H2S Gas Sensor Based on WO3-Coated Sno2 Nanowires
Tran Thi Ngoc Hoa a,b, Dang Thi Thanh Le a, Nguyen Van Toan a,b,c, Nguyen Van Duy a, Chu Manh Hung a, Nguyen Van Hieu c, Nguyen Duc Hoa a
a: International Training Institute for Materials Science, Hanoi University of Science and Technology, 1 Dai Co Viet, Hai Ba Trung, Hanoi, Vietnam
b: Hanoi Medical University, 1 Ton That Tung, Dong Da, Hanoi, Vietnam
c: Faculty of Electrical and Electronic Engineering, Phenikaa University, Yen Nghia, Hanoi, Vietnam
Abstract
The enhancement of the H2S gas-sensing performance of SnO2 nanowires is vital for practical application. In this study, H2S gas sensors based on WO3-coated SnO2 nanowires were fabricated through a two-step process, namely, the chemical vapor deposition of SnO2 nanowires and then coating with WO3 by sputtering method. The morphology and crystal structures of the SnO2 nanowires coated with WO3 were investigated by field-emission scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The H2S gas-sensing properties of the fabricated sensors were tested at temperatures of 150–250°C. The SnO2 nanowires coated with 5 nm WO3 showed the best response to low-concentration H2S gas (0.1–1 ppm). At the optimal working temperature of 200°C, the sensor had a sensitivity of 177 toward 1 ppm H2S with good selectivity over the contamination of NO2, NH3, H2, and CO gases. We also discussed the gas-sensing mechanism of the fabricated sensor based on the n–n heterojunction between n-type SnO2 and n-type WO3, which formed a thick depletion layer and thus enhanced the sensitivity to H2S. (Read More)
2. Novel Numerical Approach for Free Vibration of Nanocomposite Joined Conical–Cylindrical–Conical Shells
Dinh Gia Ninh a,b, Vu Tri Minh a,b, Nguyen Van Tuan c, Nguyen Chi Hung a,b, Dinh Van Phong a
a: School of Mechanical Engineering, Hanoi University of Science and Technology, 1 Dai Co Viet, Hai Ba Trung, Hanoi, Vietnam
b: Group of Materials and Structures, Hanoi University of Science and Technology, 1 Dai Co Viet, Hai Ba Trung, Hanoi, Vietnam
c: Department of Mechanical Engineering and Mechatronics, Phenikaa University, Yen Nghia, Hanoi, Vietnam
Abstract
The free vibration of conical–cylindrical shells made of carbon nanotube (CNT) reinforced to polymer is investigated by a semi-analytical method based on the theory of Donnell type with a moderately large deformation. The uniform and functionally graded CNTs are used to reinforce through the thickness of the shells. An exact power series solution using the regression formulas (TRF) is chosen to solve the equations of motion, and then boundary and continuity conditions is utilized to obtain the algebraic equations; therefore the fundamental frequencies are found. The accuracy of the method depends on the number of terms of the solution and the error of the computer. The codes of Wolfram Mathematica and MATLAB software are built to give the optimization of the results of the problem. The obtained results are compared with the previous results for the models including cylindrical shells, conical shells, and conical–cylindrical shells. Furthermore, the obtained results have good agreement with the experimental and Finite Element Analysis (FEA) results. The effects of geometrical parameters and material characteristics are carefully taken into account in the present study. The obtained results can be used as benchmark solutions for serving in further research and have the valuable applications in submarine shell, UAV, shells in the aerospace and civil engineering. (Read More)
3. Evolutionary Algorithms to Optimize Task Scheduling Problem for the IoT Based Bag-of-Tasks Application in Cloud-Fog Computing Environment
Binh Minh Nguyen a, Huynh Thi Thanh Binh a, Tran The Anh b, Do Bao Son c
a: School of Information and Communication Technology, Hanoi University of Science and Technology, 1 Dai Co Viet, Hai Ba Trung, Hanoi, Vietnam
b: School of Computer Science and Engineering, Nanyang Technological University, 50 Nanyang avenue, Singapore 639798, Singapore
c: Faculty of Information Technology, University of Transport Technology, 54 Trieu Khuc, Thanh Xuan, Hanoi, Vietnam
Abstract
In recent years, constant developments in Internet of Things (IoT) generate large amounts of data, which put pressure on Cloud computing’s infrastructure. The proposed Fog computing architecture is considered the next generation of Cloud Computing for meeting the requirements posed by the device network of IoT. One of the obstacles of Fog Computing is distribution of computing resources to minimize completion time and operating cost. The following study introduces a new approach to optimize task scheduling problem for Bag-of-Tasks applications in Cloud–Fog environment in terms of execution time and operating costs. The proposed algorithm named TCaS was tested on 11 datasets varying in size. The experimental results show an improvement of 15.11% compared to the Bee Life Algorithm (BLA) and 11.04% compared to Modified Particle Swarm Optimization (MPSO), while achieving balance between completing time and operating cost. (Read More)