- 标题
- 摘要
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- 实验方案
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Characterization and analysis on micro-hardness and microstructure evolution of brass subjected to laser shock peening
摘要： In view of the temperature distribution of the high-temperature geothermal tunnels, the surrounding rock temperature was divided into four grades (40 (cid:1)C, 60 (cid:1)C, 80 (cid:1)C and 100 (cid:1)C) to simulate the hot-dry environment. Using the standard curing environment as a reference condition, the mechanical properties and pore structure characteristics of concrete for shotcrete use under hot-dry environments at different temperatures were studied by mechanical and mercury intrusion porosimetry (MIP) tests. Fractal dimension of pore structure was calculated through the fractal model based on thermodynamic method. Bivariate correlation analysis was conducted on the curing temperature and the pore structure parameters. The results show that the 40 (cid:1)C hot-dry environment is conducive to enhance the mechanical properties of concrete and optimize its pore structure at the age of 1d. However, the hot-dry environments after 7 days will deteriorate the mechanical properties and pore structure of concrete, and the higher the temperature, the more obvious the deterioration. There is a significant correlation between curing temperature and porosity of capillary pores, median pore diameter, average pore diameter and fractal dimension.
关键词： Pore structure,Surrounding rock temperature,Mechanical property,Fractal dimension,Concrete for shotcrete use,High-temperature geothermal tunnel,Hot-dry environment
更新于2025-09-11 14:15:04
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Facile green and one-pot synthesis of purple perilla derived carbon quantum dot as a fluorescent sensor for silver ion
摘要： Coalbed methane (CBM) reservoir pore structure is extremely complex and heterogeneous. With the fractal theory, the geometric and structural characteristics of the pore structure could be quanti?ed. However, few studies have aimed to understand the fractal features of compositional-based macrolithotypes (bright, semi-bright, semi-dull, and dull coals). In this work, samples from the Hancheng area, in the southeastern Ordos Basin, China, were collected to investigate the fractal features of pore structures for macrolithotypes and calculate fractal dimensions (Da1 and Da2 for adsorption pores; Ds1 and Ds2 for seepage pores) based on low temperature N2 adsorption and mercury intrusion data, respectively. Meanwhile, the impact of the fractal dimensions on the gas adsorption capacity and the seepage ability were discussed. The results demonstrate that when bright coal turns into dull coal, the vitrinite content, helium permeability, and gas adsorption capacity gradually decrease, while the coal density, mineral content, and ash yield increase. Since the Da1 and Ds1 either deviate from the natural fractal dimension (2 < D < 3) or have a poor correlation with macrolithotypes, Da2 and Ds2 are regarded as the adsorption and seepage pore fractal dimensions, respectively. Of all the coal macrolithotypes, bright coal has the smallest BET speci?c surface area and micropore proportion, which results in the smallest fractal dimension Da2, while for the dull coal, this is just the contrary; due to the higher mineral content, a higher Da2 of the dull coal indicates a more complicated adsorption pore structure, and the coal with a larger Langmuir volume has a smaller Da2. For the seepage pores, when the bright coal turns into dull coal, the macropore proportion gradually decreases, but the pore proportion tends toward equilibrium, and the mercury withdrawal e?ciency increases; the dull coal has a larger Ds2, indicating a more complex seepage pore structure than that in the bright coal. Due to the decreasing macropore proportion and mineral ?lling, Ds2 demonstrates an obvious negative correlation with the helium permeability and macropore proportion.
关键词： Adsorption pore,Pore structure,Seepage pore,Fractal dimension,Coal macrolithotype
更新于2025-09-11 14:15:04
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Defect induced thermal-plasma coupling damage in optical films under nanosecond pulse laser irradiation
摘要： Ten prestressed concrete beams were designed and manufactured, which were preloaded with 40% and 60% ultimate load to crack. Then the beams were reinforced by CFRP and immersed in chloride condition for 120 days. After that, a four-point bending test was performed. Based on the statistics and fractal theories, the cracking mechanism, distribution and shapes of cracks in mid span were researched, considering the initial cracks, CFRP reinforcement and chloride corrosion. The test results demonstrate that CFRP has a restraining effect on the cracks, and the effect decreases with the increases of heights. The crack widths conform to normal distribution, and the dispersion coefficient, average widths and characteristic widths decrease with the increase of the heights, and the three parameters of CFRP reinforced beams at the same heights are all smaller than those of unreinforced beams. The fractal dimensions of cracks in unreinforced beams and CFRP reinforced beams increase linearly and exponentially with load steps, respectively. CFRP reinforcement and Chloride corrosion makes the fractal dimension increase, respectively. The corrosion effect of chloride can be weakened by CFRP. Therefore, the fractal dimensions of beam cracks can be used to evaluate the damage caused by several coupled load conditions.
关键词： chloride corrosion,cracks,fractal dimension,prestressed concrete beams,CFRP
更新于2025-09-11 14:15:04
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - Design and analysis of Ultra-Wide Band (UWB) antennas based on metamaterial
摘要： In this paper, a numerical study on the performance of an Ultra-Wide Band (UWB) antennas constructed, the design and analysis of UWB antennas based on metamaterial of miniaturized geometries for different wireless applications is proposed. Computer Simulation Technology/Microwave Studio (CSTMWS) software packages based on Finite Integration Technique (FIT) are used to build and analyze the proposed technique to design the metamaterial unit cells and the antenna structures. In this paper, to improve the performance of UWB antennas in term of bandwidth, gain, radiation pattern, and frequency resonance, metamaterial are proposed and constructed from the patches and ground plane mounted on the same substrate of the antenna structures. A systematic study based on FIT of CST MWS formulation is presented, therefore, a specific antenna parameters are readjusted for optimal design approach of the proposed antennas using optimization processes. Two prototypes have been constructed, the first prototypes using four Fractal cells applied at the top of circular shape UWB antenna and the ground plane. The second prototype is made of four modified Split Ring Resonator (SRR) and Capacitive Loaded Strip (CLS) and wire. The performance of the two prototypes evaluated numerically using CST MWS formulation. Different parametric studies based on numerical simulations is invoked to arrive to the optimal design through monitoring the effects of adding the metamaterial structures on the performance of the proposed antennas. Therefore, these parametric studies are optimized to achieve maximum antenna bandwidth with relatively best gain.
关键词： Fractal cell,Metamaterial,UWB antennas,CST MW,S11,SRR
更新于2025-09-11 14:15:04
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On the Fractal Absorption Spectra of Polymers in the Low-Frequency Part of the Terahertz Range
摘要： The power dependence α(ν) ∝ νμ, where μ > 0 is the power exponent which is noninteger in the general case, is observed for amorphous polymers with a small absorption coe?cient α in the low-frequency part of the terahertz range, which approximately corresponds to the frequencies ν from 0.1 to 2–3 THz. This dependence is fractal, which is due to the fractal structure of the polymer macromolecules. In this work, we ?nd the power-law index at room temperature for the absorption coe?cient of some amorphous polymers. This index is determined on the basis of the dynamics of transmission of a broadband picosecond terahertz pulse through the polymer sample, i.e., using the method of the pulse terahertz spectroscopy in the time-domain representation.
关键词： terahertz range,fractal absorption spectra,polymers,fractal structure,power-law index
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - The Decomposition-Reconstitution Theorem for Scattering Computation from Random Rough Surface
摘要： In this paper, the decomposition-reconstitution theorem is introduced to solve the electromagnetic scattering field from the random rough surface. The random rough surface is decomposed into a series of fractal described by sinusoidal basis functions and the scattering fields are computed for each fractal. The scattering field of surface is reconstituted by vector-superposing the scattering fields of fractal. The theorem is demonstrated by the numerical simulation using FDTD. It shows that the difference of both results is a little in the range of the calculation error. This theorem was applied to solving the backscattering coefficient of the soil surface of Qionglai Sichuan, the result generally coincides with the ground-based scatter-meter measurement data and AIEM.
关键词： Fractal,Decomposition-Reconstitution Theorem,Numerical Simulation,Electromagnetic Scattering
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Evaluating Scattered Electromagnetic Field from Fractal Surface Using its Components
摘要： In this paper, a novel method is proposed to evaluate the scattered field from rough surfaces by decomposition-reconstitution. The extended boundary condition method (EBCM) is employed in conjunction with a Weierstrass Mandelbrot (WM) function for fractal surface profile and its components. WM function can be decomposed into a series of sinusoidal profile. The properties of the sinusoidal profile and WM function to be periodic and almost periodic allow the deriving respective amplitudes of the scattered Floquet modes. The superposition of scattered fields from each sinusoidal component is consistent with the scattered field from WM surface. The result has compared with AIEM in backscattering coefficients. Thus, by calculating the scattered information for each sinusoidal component of the rough surface, we can obtain the overall scattered field.
关键词： Fractal,Scattered field superposition,Rough surface decomposition,Extended Boundary Condition Method,Electromagnetic Scattering
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Backscattering from Fractal Rough Surfaces Under Tapered Wave Illumination
摘要： In this paper, a method of Numerical Maxwell Model in 3D Simulations (NMM3D) is used to evaluate the backscattering information of fractal rough surfaces. Weierstrass Mandelbrot function is employed to generate natural rough surfaces. Quantitative analyses are demonstrated on the relation of fractal parameters and rough surface parameters. In order to eliminate the unwanted edge effects, a tapered incident wave model is built to illuminate the surface models with the use of sampling strategy. Method of Moments is employed to evaluate the backscattered fields. The results are demonstrated and show a good agreement with AIEM model.
关键词： Tapered wave,Backscattering coefficient,Fractal surface,NMM3D,Method of Moments
更新于2025-09-10 09:29:36
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Grafting of derivatives of naphthalic anhydride onto amine-modified surfaces of dense nanosilica and their fractal features for luminescent performance
摘要： The surfaces of density nano-silica spheres (DNSS) was modified using amine groups, and then novel luminescent DNSS-based materials were successfully synthesized via post-grafting various capacities of perylene-3.4.9.10-tetracarboxylic-dianhydride (PTD) and 4-amino-1,8-naphthalic anhydride (ANA). Meanwhile, their structures and properties were characterized by XRD, SAXS, TEM, N2 sorption, FT-IR, TG-DTG, Photoluminescence and elemental analysis, as well as time-resolved decays. The results demonstrate that the ANA or PTD is uniformly distributed in the presence of outer surface of amine-modified DNSS. Two characteristic peaks centered at 525 nm and 560 nm with various amounts of surface-grafted PTD belong to aggregate states, comparably, the emission peak for ANA-DNSS samples presents the blue-shift from 520 nm to 504 nm with increasing amount of indicating the dispersion behaviors of ANA from aggregating to monolayer state. surface-grafted ANA, Meanwhile, the fluorescence decay lifetime is around 4.49ns for ANA-DNSS-10, 9.85ns for PTD-DNSS-10, longer than 3.99ns for NA-DNSS-10 in our previous report. Specially, the SAXS patterns show the increase tendencies for surface fractal value with increasing amount PTD or ANA, suggesting the structural irregularities of obtained hybrid materials for before and after surface grafting. These observations demonstrate that the surface effect in the APTES-DNSS matrix play an important role on the fluorescent behaviors.
关键词： Naphthalic anhydride,Surface fractal,Fluorescence,Nanosilica spheres
更新于2025-09-10 09:29:36
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Compact high gain UWB antenna using fractal geometry and UWB-AMC
摘要： A miniaturized fractal antenna using Coplanar Wave Guide (CPW) fed and ultrawideband (UWB)-artificial magnetic conductor (AMC) for ultra wideband and Active integrated application is designed and presented. This antenna covers frequency range from 2.5 to 10 GHz with ultrabandwidth of 7.5GHz and return loss well below ?10 dB over the entire band of application. The antenna has an average gain of 3.35 dB without AMC and 7.7 dBi with UWB-AMC. Physical dimension of the proposed antenna is (27 × 28 mm × 1.6) mm3 and for UWB-AMC is (40 × 40 × 1.6) mm3. Complet set of UWB-antenna and A.MC- is fabricated using FR.-4 substrate with εr = 4.4, d = 0.0001and thickness (h) = 1.6 mm. Ansys HFSS Tool is used to analyze and optimize the parameters of antenna and UWB-AMC. Vector Network Analyzer is used to validate the experimental result with simulation parameter of proposedantenna.
关键词： CPW feed,fractal geometry,ultrawideband artificial magnetic conductor (UWB-AMC),Sierpinski carpet
更新于2025-09-10 09:29:36