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With digital equipment becoming increasingly networked, either on wired or wireless networks, for personal and professional use alike, distributed software systems have become a crucial element in information and communications technologies. The study of these systems forms the core of the ARLES' work, which is specifically concerned with defining new system software architectures, based on the use of emerging networking technologies. In this context, we concentrate on the study of distributed systems which bring to life the vision of ubiquitous computing systems, also known as ambient intelligence.

반도체 공정 overview

Electrically–transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high–performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical pers...

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

Diffusion, coalescence, and reconstruction of vacancy defects in graphene layers are investigated by tight-binding molecular dynamics (TBMD) simulations and by first principles total energy calculations. It is observed in the TBMD simulations that two single vacancies coalesce into a 5-8-5 double vacancy at the temperature of 3000 K, and it is further reconstructed into a new defect structure, the 555-777 defect, by the Stone-Wales type transformation at higher temperatures. First principles calculations confirm that the 555-777 defect is energetically much more stable than two separated single vacancies, and the energy of the 555-777 defect is also slightly lower than that of the 5-8-5 double vacancy. In TBMD simulation, it is also found that the four single vacancies reconstruct into two collective 555-777 defects which is the unit for the hexagonal haeckelite structure proposed by Terrones et al. [Phys. Rev. Lett. 84, 1716 (2000)].

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Diffusion, Coalescence, and Reconstruction of Vacancy Defects in Graphene Layers

Hydrogen atom makes graphene magnetic Graphene has many extraordinary mechanical and electronic properties, but it's not magnetic. To make it so, the simplest strategy is to modify its electronic structure to create unpaired electrons. Researchers can do that by, for example, removing individual carbon atoms or adsorbing hydrogen onto graphene. This has to be done in a very controlled way because of a peculiarity of the graphene's crystal lattice, which consists of two sublattices. Gonzales-Herrero et al. deposited a single hydrogen atom on top of graphene and used scanning tunneling microscopy to detect magnetism on the sublattice lacking the deposited atom (see the Perspective by Hollen and Gupta). Science, this issue p. 437; see also p. 415 Scanning tunneling microscopy shows that a hydrogen atom deposited on graphene makes the complementary sublattice magnetic. [Also see Perspective by Hollen and Gupta] Isolated hydrogen atoms absorbed on graphene are predicted to induce magnetic moments. Here we demonstrate that the adsorption of a single hydrogen atom on graphene induces a magnetic moment characterized by a ~20–millielectron volt spin-split state at the Fermi energy. Our scanning tunneling microscopy (STM) experiments, complemented by first-principles calculations, show that such a spin-polarized state is essentially localized on the carbon sublattice opposite to the one where the hydrogen atom is chemisorbed. This atomically modulated spin texture, which extends several nanometers away from the hydrogen atom, drives the direct coupling between the magnetic moments at unusually long distances. By using the STM tip to manipulate hydrogen atoms with atomic precision, it is possible to tailor the magnetism of selected graphene regions.

/pdf/atomic-scale-control-of-graphene-magnetism-by-using-hydrogen-53d9rq6gri.pdf

Atomic-scale control of graphene magnetism by using hydrogen atoms

C2N monolayer as NH3 and NO sensors: A DFT study

Motivated by the recent realization of two-dimensional (2D) nanomaterials as gas sensors, we have investigated the adsorption of gas molecules (SO2, NO2, HCN, NH3, H2S, CO, NO, O2, H2, CO2, and H2O) on the graphitic GaN sheet (PL-GaN) using density functional theory calculations. It is found that among these gases, only SO2 and NH3 gas molecules are chemisorbed on the PL-GaN sheet with apparent charge transfer and reasonable adsorption energies. The electronic properties (especially the electric conductivity) of the PL-GaN sheet showed dramatic changes after the adsorption of NH3 and SO2 molecules. However, the strong adsorption of SO2 on the PL-GaN sheet makes desorption difficult, which precludes its application to SO2 sensors. Therefore, the PL-GaN sheet should be a highly sensitive and selective NH3 sensor with short recovery time. Furthermore, the adsorption of NO (or NO2) molecules introduces spin polarization in the PL-GaN sheet with a magnetic moment of about 1 μB, indicating that magnetic properties of the PL-GaN sheet are changed obviously. Based on the change of magnetic properties of the PL-GaN sheet before and after molecule adsorption, the PL-GaN sheet could be used as a highly selective magnetic gas sensor for NO and NO2 detection.

/pdf/adsorption-of-gas-molecules-on-a-graphitic-gan-sheet-and-its-5abanoletf.pdf

Adsorption of gas molecules on a graphitic GaN sheet and its implications for molecule sensors

Properties of gas molecules (NO, NH3, and NO2) adsorbed on two-dimensional GaN with a tetragonal structure (T-GaN) are studied using first-principles methods. Adsorption energy, adsorption distance, Hirshfeld charge, electronic properties, electric conductivity, and recovery time are calculated. It is found that these three molecules are all chemisorbed on the T-GaN with reasonable adsorption energies and apparent charge transfer. The electronic properties of the T-GaN present dramatic changes after the adsorption of NO2 and NO molecules, especially its electric conductivity, but NH3 molecule hardly changes the electronic properties of the T-GaN. Furthermore, the recovery time of the T-GaN sensor at T = 300 K is estimated to be quite short for NO2 and NO but very long for NH3. Moreover, the magnetic properties of the T-GaN are changed obviously due to the adsorption of NO (or NO2) molecule. Therefore, we suggest that the T-GaN can be a prominent candidate for application as NO2 and NO molecule sensors.

Two-Dimensional Tetragonal GaN as Potential Molecule Sensors for NO and NO2 Detection: A First-Principle Study

Influence of defects and dopants on the sensitivity of arsenene towards HCN

Using density functional theory calculations, the adsorption of gaseous molecules (NO, NO2, NH3, SO2, CO, HCN, O2, H2, N2, CO2, and H2O) on the graphitic SiC monolayer and bilayer has been investig...

Qingxiao Zhou

Papers

C2N monolayer as NH3 and NO sensors: A DFT study

Adsorption of gas molecules on a graphitic GaN sheet and its implications for molecule sensors

Two-Dimensional Tetragonal GaN as Potential Molecule Sensors for NO and NO2 Detection: A First-Principle Study

Influence of defects and dopants on the sensitivity of arsenene towards HCN

Gas-Sensing Properties of the SiC Monolayer and Bilayer: A Density Functional Theory Study.