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Results 441-450 of 698 (Search time: 0.001 seconds).
  • Authors: Punam Murkute; Carmen Jiménez; Abderrahime Sekkat; Chiara Crivello; Viet Huong Nguyen; David Muñoz Rojas;  Advisor: -;  Co-Author: - (2021)

    Al-doped ZnO (AZO) has received significant attention due to its inherent properties like wide bandgap, high optical transparency, and electrical conductivity that has established its potential application in optoelectronic devices. The primary challenge in the efficient use of AZO thin films is the un-intentional formation of intrinsic defects, which deteriorate the device performance. The research community has made a significant effort to minimize these intrinsic defects and obtained high-quality films using low-cost growth techniques followed by a post-growth annealing treatment that has successfully suppressed defect states' formation. This presentation provides a comprehensive picture of the current state of knowledge on AZO's growth using spatial atomic layer deposition (SALD...

  • Authors: Tran, M.T.; Dua, N.V.; Tua, N.; Huyen, N.T.;  Advisor: -;  Co-Author: - (2022)

    ZnS has great potential as a valuable material for nanoscale devices because of its rich morphologies and unique structure. Although much effort has been made, the growth of high-quality ZnS crystal is still a challenge. In this paper, high-quality optically defect-free 1D ZnS nanostructures, including nanorods, nanowires, and nanobelts, were successfully synthesized on a large scale by a modified thermal evaporation method. XRD patterns and HRTEM images indicated that the ZnS nanostructures are single phases with hexagonal structures. Under optical excitation, all the ZnS nanostructures show intense UV emissions and almost no defect emissions at room temperature. Sharp UV lasing-like peaks with the FWHM as narrow as 2–3 nm are achieved for the ZnS nanobelts and nanowires. The optic...

  • Authors: Kissan, Mistry; Viet Huong, Nguyen; Mohamed, Arabi; Khaled, H. Ibrahim; Hatameh, Asgarimoghaddam; Mustafa, Yavuz;  Advisor: -;  Co-Author: - (2022)

    A resonant microcantilever sensor is fabricated from a zinc oxide (ZnO) thin film, which serves as both the structural and sensing layers. An open-air spatial atomic layer deposition technique is used to deposit the ZnO layer to achieve a ∼200 nm thickness, an order of magnitude lower than the thicknesses of conventional microcantilever sensors. The reduction in the number of layers, in the cantilever dimensions, and its overall lower mass lead to an ultrahigh sensitivity, demonstrated by detection of low humidity levels. A maximum sensitivity of 23649 ppm/% RH at 5.8% RH is observed, which is several orders of magnitude larger than those reported for other resonant humidity sensors. Furthermore, the ZnO cantilever sensor is self-actuated in air, an advantageous detection mode that ...

  • Authors: Tran, Quang Huy; Khai Tuan, Nguyen; Phuc Thinh, Doan; Duc Tan, Tran;  Advisor: -;  Co-Author: - (2022)

    In ultrasound tomography (UT), Born iterative method (BIM) and distorted-Born iterative method (DBIM) based on Born approximation are considered efficacious. DBIM offers faster convergence compared to BIM; however, it is more susceptible to noise and vice versa. Combined or multi-model imaging is an indispensable trend of modern imaging to detect and accurately assess tissue states. The proposed method exploits the advantages, limiting the disadvantages and increasing the imaging speed of the merging of BIM and DBIM

  • Authors: Ta, Van Ranh; Le, Hong Ky; Tran, Vinh Hung;  Advisor: -;  Co-Author: - (2022)

    This paper presents research results on direct machining of Turbine blades in Turbocharger from point cloud data. In the study, the ATOS Core 80 scanner was used to create a point cloud file from the parts of the compression Turbine blades of the sample Turbocharger. From the point cloud data file, without any processing, the machining code is programmed using Inventor Professional software. The 5-axis HASS VF2 CNC milling machine is used to perform the machining steps. To evaluate the accuracy of machining parts compared with sample parts, the CMM coordinate measuring machine is used, and the original point cloud data file is compared with the detailed point cloud data file after processing by GOM Inspect software. The research results show that it is possible to directly machine T...

  • Authors: Nguyen, Le Nhat Trang; Dao, Thi Nguyet Nga; Van, Tuan Hoang; Xuan, Dinh Ngo; Pham, Tuyet Nhung; Anh,Tuan Le;  Advisor: -;  Co-Author: - (2022)

    The present work reports efficient electrochemical nanosensors for the sensitive monitoring of 4-nitrophenol (4-NP) in tomato samples using various biosynthesized silver nanoparticles (bio-AgNPs). Three different bio-AgNP types were synthesized using natural plant extracts, including green tea (GT) leaf, grapefruit peel (GP), and mangosteen peel (MP), aiming to investigate their effects on the formation of bio-AgNPs, as well as the analytical performance of 4-NP. Based on the obtained results, it was found that the phytochemical content in various plant extracts directly influenced the physicochemical parameters of the created bio-AgNPs, such as particle size, crystallinity, and distribution. More importantly, these parameters have decisive effects on the electrocatalytic activity, ...

  • Authors: Amit, Chanda; Derick, DeTellem; Yen, Thi Hai Pham;  Advisor: -;  Co-Author: - (2022)

    Understanding the effects of phase transition, phase coexistence, and surface magnetism on the longitudinal spin Seebeck effect (LSSE) in a magnetic system is essential to manipulate the spin to charge current conversion efficiency for spincaloritronic applications. We aim to elucidate these effects by performing a comprehensive study of the temperature dependence of the LSSE in biphase iron oxide (BPIO = α-Fe2O3 + Fe3O4) thin films grown on Si (100) and Al2O3 (111) substrates. A combination of a temperature-dependent anomalous Nernst effect (ANE) and electrical resistivity measurements show that the contribution of the ANE from the BPIO layer is negligible in comparison to the intrinsic LSSE in the Si/BPIO/Pt heterostructure, even at room temperature. Below the Verwey transition of...

  • Authors: Truong V. Vu; Binh D. Pham; Phuc H. Pham; Hung V. Vu; Bo X. Tran;  Advisor: -;  Co-Author: - (2021)

    We present a numerical investigation of the breakup and freezing of a pendant hollow water drop beneath a cold curved surface. The drop contains a bubble surrounded by a shell of water that forms at an outer wetting angle of θo with the surface. The freezing begins on the cold curved surface and evolves in the direction of gravity. As it freezes, the water accumulates and forms a bulbous end at the bottom of the drop. Breakup can occur, inducing a daughter water drop. As a result, the freezing process of the remaining hollow drop attached to the surface takes less time, and the frozen drop shrinks. However, this breakup has no effect on the bubble. The various parameters under consideration include the Bond number Bo, the Stefan number St, the size of the bubble, and the angle θo. I...

  • Authors: Duc Minh, Vu; Mike, Hewitt; Duc D.Vuc;  Advisor: -;  Co-Author: - (2022)

    In this paper, we present exact methods for solving the Time Dependent Minimum Tour Duration Problem (TD-MTDP) and the Time Dependent Delivery Man Problem (TD-DMP). Both methods are based on a Dynamic Discretization Discovery (DDD) approach for solving the Time Dependent Traveling Salesman Problem with Time Windows (TD-TSPTW). Unlike the TD-TSPTW, these problems involve objective functions that depend in part on the time at which the vehicle departs the depot. As such, optimizing these problems adds a scheduling dimension to the problem. We present multiple enhancements to the DDD method, including enabling it to dynamically determine which waiting opportunities at the depot to model. With an extensive computational study we demonstrate that the resulting methods outperform all know...