After COVID-19, more and more travelers are more inclined to walk in cities, and the sensory elements of streets can have a significant impact on urban tourism. Local residents and travelers have ...different perceptions of the street and preferences for its use. The purpose of this study is to evaluate and analyse the streets from the perspective of locals and travelers.
In this study, a questionnaire was designed to obtain local residents' and travelers' evaluations of the sensory elements of the street and a quadrant analysis of the street's sensory elements was carried out using the IPA-Kano model.
The results of the study show that travelers are particularly concerned about maps and signage guidance, while local residents are more concerned about the green environment of the surroundings and how well it is maintained.
There is a difference in the indicators chosen by the two groups in the results of the comparison between locals and travelers, and this study is hoped to provide some data support for future urban managers and designers to learn from and refer to for street improvements and renewal.
Exceptionally large surface area and well-defined nanostructure are both critical in the field of nanoporous carbons for challenging energy and environmental issues. The pursuit of ultrahigh surface ...area while maintaining definite nanostructure remains a formidable challenge because extensive creation of pores will undoubtedly give rise to the damage of nanostructures, especially below 100 nm. Here we report that high surface area of up to 3,022 m(2) g(-1) can be achieved for hollow carbon nanospheres with an outer diameter of 69 nm by a simple carbonization procedure with carefully selected carbon precursors and carbonization conditions. The tailor-made pore structure of hollow carbon nanospheres enables target-oriented applications, as exemplified by their enhanced adsorption capability towards organic vapours, and electrochemical performances as electrodes for supercapacitors and sulphur host materials for lithium-sulphur batteries. The facile approach may open the doors for preparation of highly porous carbons with desired nanostructure for numerous applications.
Industry 4.0 aims to create a modern industrial system by introducing technologies, such as cloud computing, intelligent robotics, and wireless sensor networks. In this article, we consider the ...multichannel access and task offloading problem in mobile-edge computing (MEC)-enabled industry 4.0 and describe this problem in multiagent environment. To solve this problem, we propose a novel multiagent deep reinforcement learning (MADRL) scheme. The solution enables edge devices (EDs) to cooperate with each other, which can significantly reduce the computation delay and improve the channel access success rate. Extensive simulation results with different system parameters reveal that the proposed scheme could reduce computation delay by 33.38% and increase the channel access success rate by 14.88% and channel utilization by 3.24% compared to the traditional single-agent reinforcement learning method.
Silica aerogel (SA) is a nanoporous material and has attracted increasing attention in the field of thermal insulation in recent years. In this work, the thermal stability and pyrolysis ...characteristics of the methyltrimethoxysilane (MTMS) silica aerogel (MSA) prepared in pure water were investigated experimentally. The MSA shows a high thermal stability with the onset and peak temperature (
T
onset
and
T
peak
) about 417 °C and 476 °C, respectively, in the pyrolysis process. The oxidation kinetics reveals that the pyrolysis of MSA can be divided into three stages with the average apparent activation energy (
E
) of each stage being 382.8 kJ/mol, 364.4 kJ/mol, and 328.9 kJ/mol, respectively. The pre-exponential factor (
A
) has the same tendency with the
E
. The TG-FTIR analysis demonstrates that the CO
2
and H
2
O are the main volatiles during the pyrolysis process and all of them increase against the temperature. It is further observed that the production of CO
2
presents a linear increase, and the H
2
O shows an obvious two-stage form along with the temperature. Compared with other hydrophobic SAs, the MSA has a larger
T
onset
and
T
peak
and much larger
E
, indicating better thermal safety. The research outcomes provide a technical guide to analyze the thermal pyrolysis of hydrophobic SA and put a new insight to reduce their thermal hazards, which is beneficial to the development of higher-performance nanoporous silica aerogels for the thermal insulation field.
Inspired by the empirical wavelet transform method, a newly nonstationary signal analysis method–termed order-statistic filtering Fourier decomposition is proposed in this article. First, ...order-statistic filtering Fourier decomposition uses order-statistic filtering and smoothing to preprocess the Fourier spectrum of original signal, which resolves the problem of unreasonable boundaries obtained by empirical wavelet transform in segmenting the Fourier spectrum. Then, the mono-components with physical significance are obtained by adaptively reconstructing the coefficient of fast Fourier transform in each interval, which improves the problem of too many false components obtained by Fourier decomposition method. The order-statistic filtering Fourier decomposition method is compared with the existing nonstationary signal decomposition methods including empirical mode decomposition, empirical wavelet transform, Fourier decomposition method, and variational mode decomposition through analyzing simulation signals, and the result indicates that order-statistic filtering Fourier decomposition is much more accurate and reasonable in obtaining mono-components. After that, the order-statistic filtering Fourier decomposition method is compared with the mentioned methods in diagnostic accuracy through analyzing the tested faulty bearing vibration signals and the effectiveness of order-statistic filtering Fourier decomposition to the comparative methods in bearing fault identification are verified.
In this study, a water-based metamaterial absorber (MMA) with ultra-wideband microwave absorption has been proposed and investigated. Using a special structural design, the absorption rate of the ...absorber exceeds 90% in the frequency range 5.5–27.5 GHz, and the absorber’s thickness is only 5.8 mm. The angular tolerance of the MM absorber shows that the absorber works well under a wide angle of incidence. When bent, the absorber shows omnidirectional absorption characteristics and polarization insensitivity. As the proposed water MM absorber is low cost and easy to manufacture, it could be widely used in electromagnetic stealth and energy harvesting.
In this study, tailored heat treatment was employed to lower the flammability of hydrophobic silica aerogels (HSA). The effects of heat treatment temperature, time, and heating rate on the pore ...structure and flammability of the treated SA were investigated in detail. It was revealed that the heat-treated HSA still maintained a mesoporous structure with a lower tap density and a higher specific surface area. The chemical groups of the treated HSA were influenced significantly by the heat treatment temperature but were independent of the heat treatment time and heating rate. Due to the removal of organic groups, the flammability of the heat-treated SA was reduced significantly. Hence, it was demonstrated that reducing the flammability of HSA by tailored heat treatment was feasible, which can provide a simple approach to reduce the flammability of SA and benefited their expansion in thermal insulation field.
Effective and targeted prevention and treatment methods for acute kidney injury (AKI), a common clinical complication, still needs to be explored. Paricalcitol is a biologically active chemical that ...binds to vitamin D receptors in the body to exert anti-oxidant and anti-inflammatory effects. However, the molecular mechanism of the effect of paricalcitol on AKI remains unclear. The current study uses a paricalcitol pretreatment with a mouse AKI model induced by cisplatin to detect changes in renal function, pathology and ultrastructure. Results showed that paricalcitol significantly improved renal function in mice and reduced inflammatory cell infiltration and mitochondrial damage in renal tissue. Furthermore, paricalcitol markedly suppressed reactive oxygen species and malondialdehyde levels in the kidneys of AKI mice and increased the levels of glutathione, superoxide dismutase, Catalase and total anti-oxidant capacity. In addition, we detected renal necrosis and inflammation-related proteins in AKI mice by immunofluorescence and Western blot, and found that their levels were markedly decreased after paricalcitol pretreatment. Moreover, paricalcitol promotes nuclear factor erythroid 2-related factor 2 (
) in the nucleus and activates the
/heme oxygenase-1 (
) signaling pathway; while HO-1 is inhibited, the protective effect of paricalcitol on the kidney is attenuated. In conclusion, paricalcitol exerts a renoprotective effect by decreasing renal oxidative injury and inflammation through
/
signaling, providing a new insight into AKI prevention.
In this work, monolithic silica aerogels were prepared in pure water within 4 h by using MTMS as the precursor under ambient pressure drying (APD). The effects of the volume ratio of H
2
O/MTMS, CTAB ...content and NH
3
·H
2
O concentration on the properties of MTMS-based aerogels (MSA) were investigated experimentally. The realization of the rapid synthesis of MSA under APD is attributed to getting rid of the aging process, solvent exchange and surface modification. It demonstrates that the microstructure of MSA is comprised of coralloid branches. Furthermore, the greater volume ratio of H
2
O /MTMS, larger CTAB content and smaller NH
3
·H
2
O concentration cause relatively slimmer coralloid branches, smaller pores and weakened connectivity of skeletons. It also finds that the MSA with a greater volume ratio of H
2
O/MTMS presents larger Young’s modulus and smaller compressive stress, which is because of the correspondingly different microstructures. The as-prepared MSA shows a low density of 0.064 g/cm
3
and a contact angle as high as 143.4°, which provides their potentials for some engineering applications.
Methylchlorosilanes (MSCs) of the type (CH
3
)
n
SiCl
4−n
(
n
= 1, 2, 3) are usually used for surface modification of silica aerogels (SAs), in which the quantity of Si–Cl and Si–CH
3
groups deeply ...affects the properties of prepared SAs. In this work, methyltrichlorosilane (MTCS,
n
= 1), dimethyldichlorosilane (DMDCS,
n
= 2), and trimethylchlorosilane (TMCS,
n
= 3) were used to modify wet gels and the effects of Si–Cl and Si–CH
3
groups’ quantity on microstructures and surface properties were explored in detail. It turned out that the MTCS modified SA (MSA) possessed the most compact and nonuniform three-dimensional nanostructure among the three SAs, accompanied by the biggest density of ~ 0.14 g/cm
3
. Further investigations demonstrated that all the three SAs had similar BET surface area of about 900 m
2
/g and average pore size of 10–15 nm. Though FTIR analysis presented the discrepancies obviously among the three SAs, the thermal stability of the three SAs was similar, with the onset and peak temperatures in the exothermic reaction of methyl groups being ~ 240 °C and ~ 270 °C, respectively. The best hydrophobicity belonged to the TSA, verified by the biggest contact angles of 155°. Thus, all these indicated that the properties of the three SAs were deeply related to the quantity of Si–Cl and Si–CH
3
groups in MCS.
Graphical abstract
PDF
