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- Viet-Thanh Pham (4)
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To further reduce the driving field of Bi1/2Na1/2TiO3-based piezoceramics to meet the requirements for real actuators applications, SrTiO3 modified 0.99Bi1/2Na1/2TiO3-0.01LaFeO3 piezoceramics were synthesized. The 0.79Bi1/2Na1/2TiO3-0.01LaFeO3-0.20SrTiO3 provides the large electrostrains of 405 pm/V at 1.7 kV/mm and 565 pm/V at 2 kV/mm, which are triable values for actuator applications in non-textured Bi1/2Na1/2TiO3-based piezoceramics. |
Given that mental health issues are acute in Asian countries, particularly Japan and Korea, and university students are more vulnerable to depression than the general population, this study aims to examine the landscapes of scientific research regarding depressive disorders among university students and evaluate the effectiveness of international collaboration and funding provision on the scientific impact in Korea, Japan, and China. Based on articles retrieved from the Web of Science database during the period 1992–2018, we found that the number of scientific publications, international collaborations, and allocated funds regarding depressive disorder among university students in China (97 articles, 43 international collaborations, and 52 funds provided, respectively) overwhelmingl... |
We investigate several definitions of the time-dependent spectral function A(ω,t) of the Anderson impurity model following a quench and within the time-dependent numerical renormalization group (TDNRG) method. In terms of the single-particle two-time retarded Green function Gr(t1,t2), the definitions we consider differ in the choice of the time variable t with respect to t1 and/or t2 (which we refer to as the time reference). In a previous study [H. T. M. Nghiem et al., Phys. Rev. Lett. 119, 156601 (2017)], we investigated the spectral function A(ω,t), obtained from the Fourier transform of Im[Gr(t1,t2)] with respect to the time difference t′=t1−t2, with time reference t=t2. Here, we complement this work by deriving expressions for the retarded Green function for the choices t=t1 an... |
International collaboration contributes significantly to improving scientific performance in Vietnam, but it also results in Vietnamese researchers depending on foreign partners to get their work published. The current study is an initial effort to examine the domestic research capability of Vietnam’s Social Science and Humanities (SSH) disciplines through scientific productivity. The research focuses on investigating various aspects, including leading Vietnamese authors, solo authors, and gender difference, as well as international and domestic collaboration networks. The study extracts the data of 2040 Vietnamese SSH authors, 1981 foreign authors, and 3160 publications during the period of 2008–2019, from the exclusive Social Sciences and Humanities Peer Awards (SSHPA) database. F... |
Fabrication of a high-performance room-temperature (RT) gas sensor is important for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices. Herein, we developed a NO2 gas sensor based on ultrathin MoS2 nanoflowers with high sensitivity at RT. The MoS2 flower-like nanostructures were synthesised via a simple hydrothermal method with different growth times of 24, 36, 48, and 60 h. The synthesised MoS2 nanoflowers were subsequently characterised by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy. The petal-like nanosheets in pure MoS2 agglomerated to form a flower-like structure with Raman vibrational modes at 378 and 403 cm−1 and crystallisation in ... |
We reconsider the question of electric charge quantization, which leads to the existence of a dark charge nontrivially unified with weak isospin in a novel gauge symmetry, SU(3)C ⊗SU(2)L⊗U(1)Y ⊗U(1)N , where Y and N determine the electric and dark charges, respectively. The new model provides neutrino masses and dark matter appropriately, a direct consequence of the dark dynamics. We diagonalize the fermion, scalar, and gauge sectors as well as obtain relevant interactions, taking into account the kinetic mixing of U(1)Y,N gauge bosons. The new physics signals at colliders are examined. The dark matter observables are discussed. |
The Internet of Things (IoT) is increasingly creating new market possibilities in several industries’ sectors such as smart homes, smart manufacturing, and smart cities, to link the digital and physical worlds. A key challenge in an IoT system is to ensure network performance and cost-efficiency when a plethora of data is generated and proliferated. The adoption of Network Function Virtualization (NFV) technologies within an IoT environment enables a new approach of providing services in a more agile and cost-efficient way. We address the problem of traffic engineering with multiple paths for an NFV enabled IoT system (vIoT), taking into account the fluctuation of traffic volume in various time periods. We first formulate the problem as a mixed linear integer programming model for f... |
In recent years designing new multistable chaotic oscillators has been of noticeable interest. A multistable system is a double-edged sword which can have many benefits in some applications while in some other situations they can be even dangerous. In this paper, we introduce a new multistable two-dimensional oscillator. The forced version of this new oscillator can exhibit chaotic solutions which makes it much more exciting. Also, another scarce feature of this system is the complex basins of attraction for the infinite coexisting attractors. Some initial conditions can escape the whirlpools of nearby attractors and settle down in faraway destinations. The dynamical properties of this new system are investigated by the help of equilibria analysis, bifurcation diagram, Lyapunov expo... |
In an arbitrary system subjected to a quench or an external field that varies the system parameters, the degrees of freedom increase double in comparison to that of an isolated system. In this study, we consider the quantum impurity system subjected to a quench, and measure the corresponding time-evolution of the spectral function, which is originated from the time-resolved photoemission spectroscopy. Due to the large number of degrees of freedom, the expression of the time-dependent spectral function is twice much more complicated than that of the time-independent spectral function, and therefore the calculation is extremely time-consuming. In this paper, we estimate the scale of time consumption of such calculation in comparison to that of time-independent calculation, and present... |
Investigating new chaotic flows has been a hot topic for many years. Studying the chaotic attractors of systems with various properties illuminates a lamp to reveal the vague of the generation of chaotic attractors. A new chaotic system in the spherical coordinates is proposed in this paper. The system’s solution is inside a predefined sphere, and its attractor cannot cross the sphere. Investigation of equilibrium points of the system shows that the system has eight equilibria, and all of them are saddle. Bifurcation analysis of the system depicts the period-doubling route to chaos with changing the bifurcation parameter. Also, Lyapunov exponents in the studied interval of the bifurcation parameter are discussed. The basin of attraction of the system is investigated to show the sens... |
