Noise reduction is an important development direction for aircrafts and wind turbines. Owl wings have three unique morphological characteristics (leading-edge serrations, trailing-edge serrations and ...velvet-like surfaces) that effectively suppress aerodynamic noise in low Reynolds numbers. Among them, trailing-edge serrations are widely considered the most effective noise-reduction method. Although different serrations have been studied, the quantitative relationship and influence mechanism between the serration shape, wavelength and amplitude are poorly understood. The acoustic characteristics of asymmetrical aerofoils with different trailing-edge serrations have not been fully studied. This work investigates the flow characteristics and acoustic scattering mechanisms of novel owl-based aerofoils with different trailing-edge serrations. A sensitivity analysis is utilized to quantitatively investigate the influence and interaction mechanisms of the shape, wavelength and amplitude in trailing-edge noise reduction. Numerical simulations of the transient flow over the aerofoil are performed via the large eddy simulation method, and the acoustic far-field is obtained by solving the Ffowcs Williams and Hawkings equation. The results indicate that the sawtooth and sinusoidal serrations provide the most significant noise reduction effects; the maximum noise reduction is 8.74 dB. The wavelength and amplitude play similar roles, but the amplitude has relatively greater influence. For the sawtooth and sinusoidal serrations, the large-scale vortex structures are broken into many small-scale spiral vortex structures due to the presence of the sharp serration tip. The serrations can effectively reduce the coherence of the turbulent fluctuations due to spanwise variations in the edge and may be the main reason for noise suppression. The original owl-based aerofoil generates more low-frequency noise and less high-frequency noise than aerofoils with trailing-edge serrations. The peak noise frequencies of all aerofoils are approximately 400 Hz; hence, low-frequency noise is a dominant influence in noise generation. Furthermore, the acoustic sources generated by transient pressure fluctuations are mainly located on the serration root.
The evolution of China's industrial structure from 2010 to 2021 is assessed based on the rationalization and sophistication of its industries. The Theil index quantifies spatial variability, while ...the Quadratic Assignment Procedure (QAP) investigates if changes in industrial structure imbalance will increase wealth disparity. The study's findings indicate a noticeable spatial imbalance in industrial structure change. The overall level of common wealth is low but steadily increasing, following a stepped-down structure of "east-center-west." Additionally, the north and south regions exhibit a pattern of "high in the north and low in the south." There is a pattern of higher values in the north and lower values in the south. In terms of common wealth and its dimensions, there is a ladder-like pattern with high values at the core decreasing towards the west. Between 2010 and 2021, the common wealth development shifted from a lower level to a higher one. Beijing, Jiangsu, and Shanghai constantly ranked in the top echelon, while Guangxi remained in the fifth echelon. The speed and difficulty of transitioning between echelons vary. Moving from the fourth echelon to the third echelon takes longer, while transitioning from the third echelon to higher echelons presents tougher challenges. Spatial imbalances in industrial structure changes widen the gap in common wealth. In particular, the impact of the gap in the advanced industrial structure on the common wealth gap is significantly higher than that of the gap in industrial rationalization. Reducing disparities in advanced industrial structure is more effective in reducing the overall wealth gap.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The interaction between water and biomolecules including peptides is of critical importance for forming high‐level architectures and triggering life's functions. However, the bulk aqueous environment ...has limitations in detecting the kinetics and mechanisms of peptide self‐assembly, especially relating to interactions of trace water. With ionic liquids (ILs) as a nonconventional medium, herein, it is discovered that trace amounts of water play a decisive role in triggering self‐assembly of a biologically derived dipeptide. ILs provide a suitable nonaqueous environment, enabling us to mediate water content and follow the dynamic evolution of peptide self‐assembly. The trace water is found to be involved in the assembly process of dipeptide, especially leading to the formation of stable noncovalent dipeptide oligomers in the early stage of nucleation, as evident by both experimental studies and theoretical simulations. The thermodynamics of the growth process is mainly governed by a synergistic effect of hydrophobic interaction and hydrogen bonds. Each step of assembly presents a different trend in thermodynamic energy. The dynamic evolution of assembly process can be efficiently mediated by changing trace water content. The decisive role of trace water in triggering and mediating self‐assembly of biomolecules provides a new perspective in understanding supramolecular chemistry and molecular self‐organization in biology.
Trace amounts of water are found to be predominant in triggering peptide selfassembly by using ionic liquids as an environmentally‐benign medium, which enables the dynamic evolution of peptide self‐assembly to be followed.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In recent years, a variety of ionic liquids (ILs) were found to be capable of dissolving cellulose and mechanistic studies were also reported. However, there is still a lack of detailed information ...at the molecular level. Here, long time molecular dynamics simulations of cellulose bunch in 1-ethyl-3-methylimidazolium acetate (EmimAc), 1-ethyl-3-methylimidazolium chloride (EmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl) and water were performed to analyze the inherent interaction and dissolving mechanism. Complete dissolution of the cellulose bunch was observed in EmimAc, while little change took place in EmimCl and BmimCl, and nothing significant happened in water. The deconstruction of the hydrogen bond (H-bond) network in cellulose was found and analyzed quantitatively. The synergistic effect of cations and anions was revealed by analyzing the whole dissolving process. Initially, cations bind to the side face of the cellulose bunch and anions insert into the cellulose strands to form H-bonds with hydroxyl groups. Then cations start to intercalate into cellulose chains due to their strong electrostatic interaction with the entered anions. The H-bonds formed by Cl(-) cannot effectively separate the cellulose chain and that is the reason why EmimCl and BmimCl dissolve cellulose more slowly. These findings deepen people's understanding on how ILs dissolve cellulose and would be helpful for designing new efficient ILs to dissolve cellulose.
Studies have indicated that the decrease in the extent of Arctic sea ice in recent years has had a significant impact on the Arctic ecosystem and global climate. In order to understand the evolution ...of sea ice, it is becoming increasingly imperative to have continuous observations of Arctic-wide sea ice with high spatial resolution. Passive microwave sensors have the benefit of being less susceptible to weather, wider coverage, and higher temporal resolution. However, it is challenging to retrieve accurate parameters of sea ice due to the low spatial resolution of passive microwave images. Therefore, improving the spatial resolution of passive microwave images is beneficial for reducing the uncertainty of sea ice parameters. In this paper, four competitive multi-image super-resolution (MISR) networks are selected to explore the applicability of the networks on multi-frequency Advanced Microwave Scanning Radiometer 2 (AMSR2) images of Arctic sea ice. The upsampling factor is set to 4 in the experiment. Firstly, the optimal input lengths of the image sequence for the four MISR networks are found, and then the best network on different frequency band images is further identified. Furthermore, some factors, including seasons, sea ice motion, and polarization mode of images, that may affect the super-resolution (SR) results are analyzed. The experimental results indicate that utilizing images from winter yields superior SR results. Conversely, SR results are the worst during summer across all four MISR networks, exhibiting the largest difference in PSNR of 4.48 dB. Additionally, the SR performance is observed to be better for images with smaller magnitudes of sea ice motion compared to those with larger motions, with the maximum PSNR difference of 2.04 dB. Finally, the SR results for vertically polarized images surpass those for horizontally polarized images, showcasing an average advantage of 4.02 dB in PSNR and 0.0061 in SSIM. In summary, valuable suggestions for selecting MISR models for passive microwave images of Arctic sea ice at different frequency bands are offered in this paper. Additionally, the quantification of the various impact factors on SR performance is also discussed in this paper, which provides insights into optimizing MISR algorithms for passive microwave sea ice imagery.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Due to their unique properties, ionic liquids (ILs) have attracted the academic and industrial attentions. However, recent controversies have focused on what are the main forces to determine the ...behaviors of ILs. In this work, a detailed DFT calculation was carried out to investigate the intermolecular interactions in two typical ILs, EmimBF4 and BmimPF6. The results indicate that hydrogen bonds (H-bonds) are the major intermolecular structural feature between cations and anions. Although the electrostatic force remains the major noncovalent force (70% of the total energy by energy decomposition calculation), the interaction energies calculated at different theoretical levels indicate that H-bond and van der Waals interactions cannot be ignored. However, the H-bonded capacities from natural bond orbital (NBO) delocalization energies do not show the consistent changes in the total interaction energies and number of H-bonds. Based on the canonical orbitals analysis, it is found that the σ-type orbital overlap and the partial charges transfer between anion and cation, finally, result in the significant energy reduction and rationalize the preferable location of anion, which is an essential understanding for the interaction and structure in the ion pair. Additionally, the strong agreement between the experimental IR spectra and the calculated vibrations implies that the structures of the larger ion clusters provide a reasonable depiction for bulk ILs at room temperature condition.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
We studied the arterial bypass design problem using a level set based topology optimization method. The blood flow in the artery was considered as the non-Newtonian flow governed by the Navier–Stokes ...equations coupled with the modified Cross model for the shear dependent viscosity. The fluid–solid interface is immersed in the design domain by the level set method and the fictitious porous material method. The sensitivity velocity derived by the level set based continuous adjoint method was utilized to control the evolution of the level set function. In order to accommodate the irregular analysis domains, the flow equations and the level set equations were computed on two different unstructured grids respectively. Three idealized arterial bypass configurations problems with the minimum flow shear stress objective were studied in the numerical examples. The results indicated that the optimal arterial bypass designs can effectively reduce integral of the squared shear rate in the artery and have a superior performance for the arterial grafting.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Ginsenoside Rb3 (G-Rb3) has been demonstrated to alleviate myocardial ischemia reperfusion injury (MIRI); however, it is difficult to separate G-Rb2 from its isomer G-Rb3. The current study aimed to ...compare the cardioprotective effects of G-Rb3 and the concomitant use of G-Rb3 and G-Rb2 (G-Rb3/Rb2) on MIRI in rats. A rat model of MIRI was established by ligation of the left anterior descending coronary artery and the rats were randomly divided into five groups. Prior to MIRI, G-Rb3/Rb2 (20 mg/kg), G-Rb3 (20 mg/kg) and diltiazem (DLZ; 20 mg/kg, as a positive control) were orally administered to the rats once a day for 3 consecutive days. After 30 min of ischemia and 120 min of reperfusion, cardiac function, infarct size, cardiac marker enzymes, antioxidative parameters, inflammatory factors, histopathological changes, cardiomyocyte apoptosis, and B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein and caspase-3 expression were determined using a multi-channel physiological recording system, nitrotetrazolium blue chloride, biochemical kits, radioimmunoassay kits, hematoxylin and eosin, terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay, immunohistochemistry and reverse transcription-quantitative PCR, respectively. The results indicated that treatment with G-Rb3/Rb2 significantly protected rats against MIRI, as shown by improved cardiac function, reduced myocardial ischemic area, decreased serum activities of aspartate aminotransferase, lactate dehydrogenase and creatine kinase MB, decreased serum concentrations of interleukin-6 and tumor necrosis factor-alpha, decreased malondialdehyde concentration in myocardial tissues, increased activities of superoxide dismutase, glutathione peroxidase and catalase in myocardial tissues, reduced histopathological changes in myocardial tissues, reduced number of apoptotic cardiomyocytes, and changes in the expression levels of caspase-3, Bcl-2 and Bax. In addition, the effects of treatment with G-Rb3/Rb2, G-Rb3 or DLZ were equivalent. The protective effects of G-Rb3/Rb2 on MIRI were similar to those of G-Rb3 in terms of oxidative stress, inflammatory factors and inhibition of cardiomyocyte apoptosis. Therefore, G-Rb3/Rb2 may be developed as a concomitant treatment for MIRI. Key words: ginsenosides Rb3 and Rb2, myocardial ischemia reperfusion injury, oxidative stress, inflammation, apoptosis
Multimodality imaging-guided therapy based on lanthanide-doped upconversion nanoparticles (UCNPs) has become a trend in cancer theranostics. However, the overheating effect of 980 nm excitation in ...photodynamic therapy (PDT) and the difficulties in optimizing multimodality imaging integration within a single particle are still challenges. Herein, 800 nm driven NaErF4@NaLuF4 UCNPs have been explored for optimized multimodality imaging and near-infrared (NIR) triggered PDT. Our results confirmed that the optimal ∼5 nm shell thickness can well balance the enhancement of upconversion luminescence and the attenuation of energy transfer efficiency from Er3+ towards a photosensitizer, to achieve efficient production of singlet oxygen (1O2) for PDT under 800 nm excitation. Furthermore, the as-obtained NaErF4@NaLuF4 UCNPs showed effective and applicable performance for upconversion luminescence (UCL) imaging, X-ray computed tomography (CT), and high-field T2 magnetic resonance imaging (MRI). This nanomaterial can serve as an excellent theranostic agent for multimodality imaging and image-guided therapy.
•Optimal level constitution of parameters for ORC system was obtained.•Order of system parameters’ sensitivity to the performance of ORC was revealed.•Evaporating temperature had significant effect ...on performance of ORC system.•Superheater had little effect on performance of ORC system.
In this study, a thermodynamic model of Organic Rankine Cycle (ORC) system combined with orthogonal design is proposed. The comprehensive scoring method was adopted to obtain a comprehensive index to evaluate both of the thermodynamic performance and economic performance. The optimal level constitution of system parameters which improves the thermodynamic and economic performance of ORC system is provided by analyzing the result of orthogonal design. The range analysis based on orthogonal design is adopted to determine the sensitivity of system parameters to the net power output of ORC system, thermal efficiency, the SP factor of radial inflow turbine, the power decrease factor of the pump and the total heat transfer capacity. The results show that the optimal level constitution of system parameters is determined as the working fluid of R245fa, the super heating temperature of 10°C, the pinch temperature difference in evaporator and condenser of 5°C, the evaporating temperature of 65°C, the isentropic efficiency for the pump of 0.75 and the isentropic efficiency of radial inflow turbine of 0.85. The order of system parameters’ sensitivity to the comprehensive index of orthogonal design is evaporating temperature>isentropic efficiency of radial inflow turbine>the working fluid>the pinch temperature difference of the evaporator and the condenser>isentropic efficiency of cycle pump>the super heating temperature. This study provides useful references for selecting main controlled parameters in the optimal design of ORC system.
Full text
Available for:
GEOZS, IJS, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
PDF
