Exploring two-dimensional valleytronic crystals with large valley-polarized state is of considerable importance due to the promising applications in next-generation information related devices. Here, ...we show first-principles evidence that single-layer NbX
2
(X = S, Se) is potentially the long-sought two-dimensional valleytronic crystal. Specifically, the valley-polarized state is found to occur spontaneously in single-layer NbX
2
, without needing any external tuning, which arises from their intrinsic magnetic exchange interaction and inversion asymmetry. Moreover, the strong spin-orbit coupling strength within Nb-d orbitals renders their valley-polarized states being of remarkably large (NbS
2
∼ 156 meV/NbSe
2
∼ 219 meV), enabling practical utilization of their valley physics accessible. In additional, it is predicted that the valley physics (i.e., anomalous valley Hall effect) in single-layer NbX
2
is switchable via applying moderate strain. These findings make single-layer NbX
2
tantalizing candidates for realizing high-performance and controllable valleytronic devices.
The offset quaternion linear canonical transform (OQLCT) provides a more general framework for a number of linear integral transforms in signal processing and optics, such as quaternion Fourier ...transform (QFT), fractional quaternion Fourier transform (FrQFT), and linear canonical transform (QLCT). We devote this paper to various different of uncertainty principles (UPs) for the two‐sided OQLCT, which including logarithmic UP, Heisenberg‐type UP, Hardy's UP, Beurling's UP, Entropic UP, Donoho‐Stark's UP, and Local UP. Moreover, we also prove Lieb's UP for the two‐sided short‐time offset quaternion linear canonical transform (SOQLCT).
In this paper, we consider equations involving a uniformly elliptic nonlocal operator
Aβu(x)=CN,βP.V.∫ℝNa(x−y)(u(x)−u(y))|x−y|N+βdy,$$ {A}_{\beta ...}u(x)={C}_{N,\beta}\mathrm{P}.\mathrm{V}.\underset{{\mathbb{R}}^N}{\int}\frac{a\left(x-y\right)\left(u(x)-u(y)\right)}{{\left|x-y\right|}^{N+\beta }} dy, $$
where the function
a:ℝN↦ℝ$$ a:{\mathbb{R}}^N\mapsto \mathbb{R} $$ is uniformly bounded and radial decreasing. We establish some maximum principles for
Aβ$$ {A}_{\beta } $$ in bounded and unbounded domains. Since there is no decay condition in the unbounded domain, we make use of an approximate method to estimate the singular integral to get the maximum principle. As applications of these principles, by carrying out the method of moving planes, we give the monotonicity of solutions to the semilinear equation in the coercive epigraph, which extends the result of Dipierro‐Soave‐Valdinoci Math. Ann.2017, 369(3‐4): 1283–1326. Moreover, we obtain the radial symmetry and monotonicity of solutions to the generalized Schrödinger equation in a weaker condition, which is the improvement of the result of Tang Math. Methods Appl. Sci. 2017, 40(7): 2596–2609. In addition, the maximum principle also plays an important role in acquiring monotonicity of solutions and a Liouville theorem.
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Phonon plays essential roles in dynamical behaviors and thermal properties, which are central topics in fundamental issues of materials science. The importance of first principles ...phonon calculations cannot be overly emphasized. Phonopy is an open source code for such calculations launched by the present authors, which has been world-widely used. Here we demonstrate phonon properties with fundamental equations and show examples how the phonon calculations are applied in materials science.
Solar energy is attractive because it is free, renewable, abundant and sustainable. Photocatalysis is one of the feasible routes to utilize solar energy for the degradation of pollutants and the ...production of fuel. Perovskites and their derivatives have received substantial attention in both photocatalytic wastewater treatment and energy production because of their highly tailorable structural and physicochemical properties. This review illustrates the basic principles of photocatalytic reactions and the application of these principles to the design of robust and sustainable perovskite photocatalysts. It details the structures of the perovskites and the physics and chemistry behind photocatalytic reactions and describes the advantages and limitations of popular strategies for the design of photoactive perovskites. This is followed by examples of how these strategies are applied to enhance the photocatalytic efficiency of oxide, halide and oxyhalide perovskites, with a focus on materials with potential for practical application, that is, not containing scarce or toxic elements. It is expected that this overview of the development of photocatalysts and deeper understanding of photocatalytic principles will accelerate the exploitation of efficient perovskite photocatalysts and bring about effective solutions to the energy and environmental crisis.
Quality-of-care improvement and prevention of practice errors is dependent on nurses' adherence to the principles of patient safety.
This paper aims to provide a systematic review of the ...international literature, to synthesise knowledge and explore factors that influence nurses' adherence to patient-safety principles.
Electronic databases in English, Norwegian, and Finnish languages were searched, using appropriate keywords to retrieve empirical articles published from 2010-2019. Using the theoretical domains of the Vincent's framework for analysing risk and safety in clinical practice, we synthesized our findings according to 'patient', 'healthcare provider', 'task', 'work environment', and 'organisation and management'.
Six articles were found that focused on adherence to patient-safety principles during clinical nursing interventions. They focused on the management of peripheral venous catheters, surgical hand rubbing instructions, double-checking policies of medicines management, nursing handover between wards, cardiac monitoring and surveillance, and care-associated infection precautions. Patients' participation, healthcare providers' knowledge and attitudes, collaboration by nurses, appropriate equipment and electronic systems, education and regular feedback, and standardization of the care process influenced nurses' adherence to patient-safety principles.
The revelation of individual and systemic factors has implications for nursing care practice, as both influence adherence to patient-safety principles. More studies using qualitative and quantitative methods are required to enhance our knowledge of measures needed to improve nurse' adherence to patient-safety principles and their effects on patient-safety outcomes.
Although Nb-Ir compounds are promising high-temperature structural materials due to the high melting-point, moderate density and excellent thermal stability, the structural stability and mechanical ...properties of Nb-Ir compounds are unclear. Here, we investigate the influence of Ir concentration on the structure, elastic modulus, elastic anisotropy and brittle-or-ductile behavior of Nb-Ir based compounds by using the first-principles calculations. Six Nb-Ir compounds are considered. The results show that the structural stability of Nb-Ir compounds strongly depends on the Ir concentration. In particular, NbIr3 is more thermodynamically stable than the other Nb-Ir compounds. The calculated elastic modulus of Nb-Ir compounds (except for Nb5Ir3) increases with increasing Ir concentration. The calculated bulk modulus, shear modulus and Young's modulus of NbIr3 are much larger than that of other Nb-Ir compounds. It is found that the high elastic modulus of NbIr3 is attributed to the strong and symmetrical Nb-Ir and IrIr metallic bonds. Compared to other Nb-Ir compounds, Nb3Ir and NbIr3 have the smallest percentage anisotropy in compressibility. However, Nb3Ir2 has the highest percentage anisotropy in shear. Finally, our work indicates that NbIr3 is a promising high-temperature structural material, which is potential used in advanced aerospace and automotive applications.
This study presents a broad perspective of hybrid process modeling combining the scientific knowledge and data analytics in bioprocessing and chemical engineering with a science‐guided machine ...learning (SGML) approach. We divide the approach into two major categories: ML complements science, and science complements ML. We review the literature relating to the hybrid SGML approach, and propose a systematic classification of hybrid SGML models. For applying ML to improve science‐based models, we present expositions of direct serial and parallel hybrid modeling and their combinations, inverse modeling, reduced‐order modeling, quantifying uncertainty in the process and even discovering governing equations of the process model. For applying scientific principles to improve ML models, we discuss the science‐guided design, learning and refinement. For each subcategory, we identify its requirements, strengths, and limitations, together with their published and potential applications. We also present several examples to illustrate different hybrid SGML methodologies for modeling chemical processes.
The basis of Islamic education is an operational foundation used to realize the ideal basis/source of Islamic education. The operational basis of Islamic education is of seven kinds: historical, ...sociological, economic, political and administrative, psychological, philosophical, and religious. The operational basis of everything is religion because religion is a frame for activities with Islamic nuances. This paper examines the principles of Islamic education as a scientific discipline. The results of the study show that the principles of Islamic education have qualified as a scientific discipline. Science must have the conditions for the existence of formal objects, research methods and systematics. Learners are human beings, meaning that the material object of Islamic education is human beings. However, man is also used to be an object by other sciences. Learners in Islamic education are explained in more detail. In the aspect of the method, the procedure for the Islamic education method is to pay attention to the factors that influence it, namely the purpose of Islamic education, students, situations, facilities, and personal educators. In the systematic aspect, the components of Islamic education include the objectives of Islamic education, the content/material of Islamic education, Islamic education methods, and evaluation. Thus, Islamic education is counted as an autonomous/stand-alone science because it has met the requirements as a science
High-entropy alloys are a new type of materials with excellent properties that offer a great variety of possibilities due to the large degree of freedom in element composition. In particular, ...CoCrFeNiW alloys have recently attracted a lot of attention due to their potential use in solving the long-standing problem of substituting cobalt in the cemented carbide industry. The lack of experimental and theoretical studies on these multi-components alloys hinders their optimal development. In this work, we aim at filling in this gap by studying their mechanical properties employing first-principles alloy theory and experimental techniques. By using the calculated elastic parameters, we analyzed the mechanical stability, elastic anisotropy, Debye temperature, and derived polycrystalline moduli. Moreover, we fabricated CoCrFeNi and (CoCrFeNi)0.96W0.04 and analyzed them by means of X-ray diffraction and electron backscatter diffraction. The hardness and the Young’s modulus were measured. The Young’s moduli and the lattice parameters were compared to first principles calculations and good agreement was obtained. Hardness increases with the increment of W composition.
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•High-entropy alloys are a new type of materials with excellent properties.•CoCrFeNiW is considered a potential substitution for cobalt in cemented carbides.•By using first principles and experiments, their elastic behavior is determined.•The results support the use of these alloys as substitute for Co in cemented carbides.
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