- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
3D Ln <sup>III</sup> -MOFs: displaying slow magnetic relaxation and highly sensitive luminescence sensing of alkylamines
摘要： Six new 3D isomorphous lanthanide metal organic frameworks (Ln-MOFs), [Ln2(L)2(DMF)2(H2O)4]·H2O·DMF (Ln = Pr (1); Sm (2); Eu (3); Gd (4); Dy (5); Ho (6)); H3L = 5-(2-nitro-4-carboxylphenyl)isophthalic acid, have been solvothermally synthesized and characterized. Crystallographic studies revealed that these MOFs were isomorphous 3D frameworks in which the dinuclear units with double (μ-COO)2 bridges were interlinked by the L ligands. They represent the (3,6)-connected (42·6)(43·68·82·10·12) topology. The magnetic coupling through double carboxylate bridges is antiferromagnetic in Pr-MOF (1), Gd-MOF (4), Dy-MOF (5) and Ho-MOF (6). Furthermore, Dy-MOF (5) shows slow magnetic relaxation behaviors under zero dc field. The luminescence sensing experiments demonstrated that Eu-MOF (3) displayed highly selective, well-recyclable properties and a low detection limit for sensing alkylamines in water systems. The study of Ln-MOF sensing for alkylamines is very scarce.
关键词： luminescence sensing,alkylamines,slow magnetic relaxation,3D LnIII-MOFs
更新于2025-09-19 17:15:36
-
4s to 5s and 4p photoexcitation dynamics of K atoms from the surface of helium nanodroplets: a theoretical study
摘要： We study the photodissociation of the potassium atom from a superfluid helium nanodroplet upon 5s 2S or 4p 2P excitation using the time-dependent helium density functional method (He-TDDFT). The importance of quantum effects is assessed by comparing the absorption spectrum obtained for a classical or a quantum description of the K atom. In the case of the 5s 2S ' 4s 2S excitation the difference is rather large, and we use a quantum description for the ensuing direct dissociation dynamics. In the case of the 4p 2P ' 4s 2S absorption spectrum, the difference is much smaller, hence a classical description of K is used to describe 4p 2P excitation dynamics. Excitation to the 4p 2S1/2 state leads to the direct dissociation of the K atom, while the 4p 2P3/2 state initially leads to the formation of an exciplex and the 4p 2P1/2 state to a bouncing atom above the droplet surface. Remarkably, electronic relaxation can be observed for the latter two states, leading to spin–orbit relaxation and the binding of the initially departing one-atom excimer as a ring excimer for the 2P3/2 state and to the formation of a bound, ring excimer for the 2P1/2 state.
关键词： potassium,spin-orbit relaxation,quantum effects,helium nanodroplets,exciplex formation,photodissociation
更新于2025-09-19 17:15:36
-
A study on weighing a semi-labelled sample using spectral and spatial context information
摘要： Classification of spectrally similar objects is a hard task, mainly when using moderate resolution data. Even though hyperspectral data are a useful source of information, the Hughes phenomenon is highlighted when limited number of training samples are used. For data classification and to mitigate this drawback, the number of training samples needs to be increased in the methodology. In this study, we investigated the estimation of the weights of semi-labelled samples using spectral and spatial context information by relaxation process in a two-steps methodology. The weights of semi-labelled samples in parametric classifier were estimated iteratively in the first step using spectral information only. In the second step, addition of spatial information was done by a relaxation process. This study investigated a more refined approach, improved by the inclusion of spatial context information in the relaxation process. The aim of this work was to mitigate the Hughes phenomenon and improve the separation of similar classes. The proposed methodology was tested using the data (hyperspectral image) from a study area, where the land cover classes are spectrally similar and the accurate separation of these classes was a hard task. Even though several experiments were performed, only a selected number of representative experiments are presented in this work. The results showed that the inclusion of context information can be used for the successful mitigation of the Hughes phenomenon allowing almost twice the number of bands used and increase the classification overall accuracy by up to 8%.
关键词： Hughes phenomenon,hyperspectral data,spectral and spatial context information,classification,relaxation process
更新于2025-09-19 17:13:59
-
Microhole Formation Behavior of Polypropylene Film Using CO<sub>2 </sub>Laser Irradiation
摘要： Biaxially oriented polypropylene films produced by simultaneous equi-biaxial stretching to the draw ratio of 4 (cid:186) 4 were perforated by the carbon dioxide laser under various laser fluences up to 426.3 J/cm2. After applying various laser fluences, the irradiated area was observed using a laser scanning confocal microscope. With the increase of fluence, the surface deformation with the formation of a crater surrounded by a doughnut-like rim was firstly observed at the laser fluence of 49.7 J/cm2, followed by the starting of the formation of a microhole surrounded by the rim at 113.7 J/cm2. The diameter of the microhole and the size of the rim increased rapidly with the increase of laser fluence. Mechanisms for the formation of a crater, the opening of a microhole, and the formation of surrounding rim were considered to be related to the surface tension and the shrinkage caused by molecular orientation relaxation. On the other hand, volume loss from the laser irradiated area was negligibly small at the moment of microhole opening, and started to increase rapidly when the fluence reached around 150 J/cm2. The microhole formation behavior was also observed by a high-speed camera. The velocity of microhole opening increased rapidly at first, presumably during the laser irradiation, and then slowed down after the cessation of laser irradiation. Theoretically estimated temperature distribution along the film thickness was compared with the laser perforation behavior. Starting of the deformation of film matched well with the starting of melting of the film surface. Film temperature was lower than the thermal decomposition temperature at the moment of the opening of a microhole, whereas at the moment of the starting of volume loss, film temperature was lower than the decomposition temperature estimated based on the heating rate of laser irradiated area, indicating that the decomposition and vaporization continues for a while after the cessation of laser irradiation.
关键词： microhole formation,molecular orientation relaxation,Polypropylene,laser fluence,CO2 laser,surface tension
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE International Conference on Engineering Veracruz (ICEV) - Boca del Rio, Veracruz, Mexico (2019.10.14-2019.10.17)] 2019 IEEE International Conference on Engineering Veracruz (ICEV) - Comparative of wind systems vs photovoltaic for the implementation in the electric network of Veracruz Port
摘要： This paper presents the results of three control strategies of managed energy services with home energy management system (HEMS)-integrated devices. The HEMS controls and monitors three types of managed devices: 1) heating; 2) task-speci?c; and 3) energy storage devices. Three approaches are proposed for the rolling optimization by the HEMS, namely, mixed integer linear programming (MILP), continuous relaxation (CR), and fuzzy logic controller (FLC). The CR approach is identi?ed to reduce the computational complexity of the MILP by changing the MILP into an LP solution. Three types of FLC control approaches are proposed, namely, heat-related FLC, task-related FLC, and FLC for the battery. Each control strategy is evaluated against cost optimization, computational resource, and practical implementation. The ?ndings in this paper show that all three algorithmic control strategies successfully perform cost optimization, even with inaccurate forecasting information.
关键词： mixed integer linear programming (MILP),fuzzy logic control (FLC),Continuous relaxation (CR),residential appliance,home energy management system (HEMS)
更新于2025-09-19 17:13:59
-
A comparison of sLASER and MEGA-sLASER using simultaneous interleaved acquisition for measuring GABA in the human brain at 7T
摘要： γ-Aminobutyric acid (GABA), the major inhibitory neurotransmitter, is challenging to measure using proton spectroscopy due to its relatively low concentration, J-coupling and overlapping signals from other metabolites. Currently, the prevalent methods for detecting GABA at ultrahigh field strengths (≥ 7 T) are GABA-editing and model fitting of non-editing single voxel spectra. These two acquisition approaches have their own advantages: the GABA editing approach directly measures the GABA resonance at 3 ppm, whereas the fitting approach on the non-editing spectrum allows the detection of multiple metabolites, and has an SNR advantage over longer echo time (TE) acquisitions. This study aims to compare these approaches for estimating GABA at 7 T. We use an interleaved sequence of semi-LASER (sLASER: TE = 38 ms) and MEGA-sLASER (TE = 80 ms). This simultaneous interleaved acquisition minimizes the differential effect of extraneous factors, and enables an accurate comparison of the two acquisition methods. Spectra were acquired with an 8 ml isotropic voxel at six different brain regions: anterior-cingulate cortex, dorsolateral-prefrontal cortex, motor cortex, occipital cortex, posterior cingulate cortex, and precuneus. Spectral fitting with LCModel quantified the GABA to total Cr (tCr: Creatine + Phosphocreatine) concentration ratio. After correcting the T2 relaxation time variation, GABA/tCr ratios were similar between the two acquisition approaches. GABA editing showed smaller spectral fitting error according to Cramér–Rao lower bound than the sLASER approach for all regions examined. We conclude that both acquisition methods show similar accuracy but the precision of the MEGA-editing approach is higher for GABA measurement. In addition, the 2.28 ppm GABA resonance was found to be important for estimating GABA concentration without macromolecule contamination in the GABA-edited acquisition, when utilizing spectral fitting with LCModel.
关键词： GABA,proton spectroscopy,sLASER,MEGA-sLASER,T2 relaxation,macromolecule contamination,7T,LCModel,human brain
更新于2025-09-19 17:13:59
-
Thermal Relaxation Features of Residual Stresses Arising upon Laser Shock Processing of Heat-Resistant Materials
摘要： In this paper, we study the thermal relaxation features of compressive residual stresses generated during laser-shock wave processing in high-alloyed heat-resistant Iron GH2036 alloy. A finite element modeling of thermal relaxation of the generated compressive residual stresses was performed. The features of the thermal effects on the redistribution of the compressive residual stresses in the temperature range from 200 to 650°C are studied. Based on comparative analysis, the results of the finite element modeling correlated well with the experimental data known in the literature.
关键词： residual stresses,thermal relaxation,finite element modeling,laser-shock wave treatment
更新于2025-09-19 17:13:59
-
Control of Charge Carrier Dynamics in Plasmonic Au Films by TiO <sub/><i>x</i> </sub> Substrate Stoichiometry
摘要： Plasmonic excitations in noble metals have many fascinating properties and give rise to a broad range of applications. We demonstrate, using non-adiabatic molecular dynamics combined with time-domain density functional theory, that chemical composition and stoichiometry of substrates can have a strong influence on charge dynamics. By changing oxygen content in TiO2, including stoichiometric, oxygen rich and oxygen poor phases, and Ti metal, one can alter lifetimes of charge carriers in Au by a factor of 5, and control the ratio of electron-to-hole relaxation rates by a factor of 10. Remarkably, a thin TiOx substrate alters so much charge carrier properties in much thicker Au films. Such large variations stem from the fact that the Ti and O atoms are much lighter than Au, and their vibrations are much faster at dissipating the energy. The control over a particular charge carrier and an energy range depends on the Au and TiOx level alignment, and the interfacial interaction strength. These factors are easily influenced by the TiOx stoichiometry. In particular, oxygen rich and poor TiO2 can be used to control holes and electrons, respectively, while metallic Ti affects both charge carriers. The detailed atomistic analysis of the interfacial and electron-vibrational interactions generates the fundamental understanding of the properties of plasmonic materials needed to design photovoltaic, photocatalytic, optoelectronic, sensing, nanomedical and other devices.
关键词： non-adiabatic molecular dynamics,substrate layers,time-domain density functional theory,metallic films,electron-phonon energy relaxation,surface plasmons
更新于2025-09-19 17:13:59
-
The Influence of Selected Selective Laser Sintering Technology Process Parameters on Stress Relaxation, Mass of Models, and Their Surface Texture Quality
摘要： The article presents the results of research on the impact of basic process parameters of selective laser sintering technology on the mass of the produced models (density of the sintered material—polyamide PA 2200), stress relaxation during compression determined in accordance with the ISO 3384 standard, and geometric surface structure parameters (SGPs). During the tests, the influence of process parameters such as the location of the models on the virtual construction platform (printing direction), the density of the energy supplied to the sintered layer of powder, and the layer thickness of the manufactured material layer was taken into account. The test results confirmed that the process parameters have a significant impact on the density of the model material (in the sintered state), the mechanical properties (stress relaxation during compression), and the quality of the surface texture (SGPs). The most favorable positioning variants of the models on the construction platform were determined. The most favorable thickness variants of the combined layers and the density value of the energy supplied to the sintered powder layer were selected, depending on the expected mass, strength, and SGP quality. In addition, it has been shown that it is possible to build models with reduced mass (>20%), while maintaining satisfactory mechanical and qualitative properties of the surface texture.
关键词： additive manufacturing technologies,GPS,rapid prototyping,SLS,3D printing,stress relaxation
更新于2025-09-19 17:13:59
-
Quantum Dot
摘要： Valley splitting is a key feature of silicon-based spin qubits. Quantum dots in Si/SixGe1?x heterostructures reportedly suffer from a relatively low valley splitting, limiting the operation temperature and the scalability of such qubit devices. Here, we demonstrate a robust and large valley splitting exceeding 200 μeV in a gate-defined single quantum dot, hosted in molecular-beam-epitaxy-grown 28Si/SixGe1?x. The valley splitting is monotonically and reproducibly tunable up to 15% by gate voltages, originating from a 6-nm lateral displacement of the quantum dot. We observe static spin relaxation times T1 > 1 s at low magnetic fields in our device containing an integrated nanomagnet. At higher magnetic fields, T1 is limited by the valley hotspot and by phonon noise coupling to intrinsic and artificial spin-orbit coupling, including phonon bottlenecking.
关键词： valley splitting,spin relaxation,spin qubits,molecular-beam-epitaxy,silicon,quantum dot
更新于2025-09-19 17:13:59