The connectivity of urban river networks plays an important role in cities in many aspects, such as urban water safety, water quality (WQ), and aquatic ecological balance. This study focuses on the ...river network and the Majiawan Wetland in the Chaoyang District of Beijing by establishing a two-dimensional hydrological WQ model employing various water allocation schemes between the river network and the wetland. Water circulation and WQ are the main indexes, and the effects of different scenarios on improving water circulation and WQ are simulated and compared. This study demonstrates that the addition of water replenishment at the intersection of river network and internal slow-water zones of the wetland (Scheme 2) has greater effectiveness in improving both hydrology and WQ compared to two other schemes. The water area of the Majiawan Wetland has expanded, and water velocity has increased. Using chemical oxygen demand, total nitrogen, and total phosphorus as the index values for determining the water class, the WQ of about 20% of the wetland area was reached Water Class II (domestic drinking water), with Water Class III (general industrial water) accounting for the other 80%. This study provides valuable evaluation and reference for similar areas of urban river network connectivity.
In this study, the crystallization behavior of PA6/PA66 alloys was studied using in situ FTIR spectroscopy, combined with Proj-MW2D correlation analysis and DSC measurements. The method for ...calculating the generation enthalpy of hydrogen bonds during PA6/PA66 alloys crystallization was also established via Van't Hoff analysis. The essential reason for the crystallization reduction for both PA6 and PA66 in alloys was elucidated from the perspective of hydrogen bonds. Compared with neat PA6 and neat PA66, DSC measurements showed that the crystallization ability of both PA6 and PA66 in the alloys obviously decreased. From the results of the generation enthalpies of the hydrogen bonds, it was confirmed that the capability for hydrogen bond generation of both PA6 and PA66 in PA6/PA66 alloys was significantly reduced. The molecular chain motions of PA6 and PA66 during the alloy crystallization were successfully separated using Proj-MW2D correlation FTIR spectroscopy. Two main issues were addressed. The first one is that the generating capacity of hydrogen bonds between PA6 and PA66 is actually very weak, although this type of hydrogen bond can be generated in theory. The second is that non-hydrogen bonded molecular chains of PA66 are also involved in the PA6 crystallization, and the molecular chains of amorphous state PA66 hinder the generation of hydrogen bonds between PA6 molecular chains, resulting in a significant crystallization reduction of PA6 in PA6/PA66 alloys.
The automatic classification of epilepsy electroencephalogram (EEG) signals plays a crucial role in diagnosing neurological diseases. Although promising results have been achieved by deep learning ...methods in this task, capturing the minute abnormal characteristics, contextual information, and long dependencies of EEG signals remains a challenge. To address this challenge, a positional multi-length and mutual-attention (PMM) network is proposed for the automatic classification of epilepsy EEG signals. The PMM network incorporates a positional feature encoding process that extracts minute abnormal characteristics from the EEG signal and utilizes a multi-length feature learning process with a hierarchy residual dilated LSTM (RDLSTM) to capture long contextual dependencies. Furthermore, a mutual-attention feature reinforcement process is employed to learn the global and relative feature dependencies and enhance the discriminative abilities of the network. To validate the effectiveness PMM network, we conduct extensive experiments on the public dataset and the experimental results demonstrate the superior performance of the PMM network compared to state-of-the-art methods.
The IPT system has been studied for underwater applications such as autonomous underwater vehicles (AUVs) and subsea sensors. However, it rarely comparatively shows the performance of the IPT system ...in air, freshwater, and seawater. Based on the fore‐mentioned research background, this paper presents a survey of the properties of the IPT system in different mediums. Here, a 100 W power‐level experimental IPT prototype is built and tested. The resonant frequency is set at 300 kHz with a gap range from 10 to 190 mm. The comparison is focused on the efficiency, mutual inductance, coupling coefficient, coil resistance, and quality factor of the IPT system. The IPT system is placed in air, freshwater, and seawater with the same settings. What's more, the magnetic fields of coupling coils in air, freshwater, and seawater are presented in this paper. This paper could be acted as a reference to optimize the IPT system and facilitate future IPT research for underwater applications by analysing the performance of the IPT system in different mediums. The 3D Ansys Maxwell simulation of the IPT system is also given here to study the magnetic fields.
This paper presents a survey of the properties of the IPT system in different mediums. The comparison is focused on the efficiency, mutual inductance, coupling coefficient, coil resistance, and quality factor of the IPT system.
For schistose surrounding rocks of tunnel, engineering classification of rock masses by the widely used
BQ
method in China are often inconsistent with the reality. In this study, microtests and ...uniaxial compression test were performed on three types of quartz mica schist. Microtests reveal that the schist is characterized by natural orientation and interbedded distribution of minerals and microfissures are prone to be distributed directionally along the smooth edge of flaky minerals. Mechanical test shows that the compressive strength of schist samples has U-shaped change with the varied loading direction. Moreover, the strength anisotropy degree of the schist is positively correlated with the development of schistosity planes, and the strength anisotropy increases significantly after saturation. When the direction of uniaxial load applied to the samples changes gradually, the splitting-tensile, shear-slip and shear failure occur respectively, indicating that the dominant factors affecting the strength of schist specimens are not uniform. In particular, the strength of specimens with transverse schistosity planes is less affected by the weak planes. Based on the experimental study, a new model considering the schistosity development degree was constructed, which is served as the evaluation of the basic quality of schistose rock mass. By regression analysis on 168 sets of practical data, an optimized
BQ
equation was further developed. Then a correction coefficient table was put forward based on numerical simulation, which is helpful to correctly determine the final engineering grade of surrounding rock. Case study shows that the improved
BQ
method is more reliable for classifying engineering grade of schistose surrounding rock.
Each approach for artificial cornea design is toward the same goal: to develop a material that best mimics the important properties of natural cornea. Accordingly, the selection and optimization of ...corneal substitute should be based on their physicochemical properties. In this study, three types of polyvinyl alcohol (PVA) hydrogels with different polymerization degree (PVA1799, PVA2499 and PVA2699) were prepared by freeze-thawing techniques. After characterization in terms of transparency, water content, water contact angle, mechanical property, root-mean-square roughness and protein adsorption behavior, the optimized PVA2499 hydrogel with similar properties of natural cornea was selected as a matrix material for artificial cornea. Based on this, a biomimetic artificial cornea was fabricated with core-and-skirt structure: a transparent PVA hydrogel core, surrounding by a ringed PVA-matrix composite skirt that composed of graphite, Fe-doped nano hydroxyapatite (n-Fe-HA) and PVA hydrogel. Different ratio of graphite/n-Fe-HA can tune the skirt color from dark brown to light brown, which well simulates the iris color of Oriental eyes. Moreover, morphologic and mechanical examination showed that an integrated core-and-skirt artificial cornea was formed from an interpenetrating polymer network, no phase separation appeared on the interface between the core and the skirt.
The transport of colloid in unsaturated porous media affects the migration of contaminants and thus is closely related to groundwater resources protection. To figure out the combined effects of grain ...size, colloid concentration and injection flow rate on montmorillonite colloid transport characteristics in unsaturated quartz sand, a total of 27 sets of column experiments were conducted with three kinds of quartz sand (20, 40, 60 mesh), three flow rates (1.98, 3.96, 5.94 cm
3
/min) and three colloid concentrations (300, 600, 900 mg/L), using three packed columns with the inner diameter of 11 cm and the height of 40 cm. The experimental results showed that the transport of Na-montmorillonite colloid particles in the unsaturated quartz sand columnoccurred with significant retention. In the 20 mesh quartz sand column, the average peak values of the penetration curves for low and high concentration colloidal solutions of 300 and 900 mg/L increased by 44% and 27%, respectively, as the flow rate increased from 1.98 to 5.94 cm
3
/min. The average peak value of the colloidal solution with concentration 300 mg/L increased 17% more than that of the colloidal solution with 900 mg/L for increasing flow rate. When the injection flow rate of the colloidal solution was increased from 1.98 to 5.94 cm
3
/min, the effect of flow rate on colloidal transport was the most obvious, followed by the effect of media particle size, while the effect of colloidal solution concentration was the least. The calculation based on the total potential energy of Derjaguin-Landau-Verwey-Overbeek (DLVO) and collision efficiency further explained the retention of colloids in unsaturated porous media.
Offshore wind power has become an important trend in global renewable energy development. Based on a particle swarm optimization (PSO) algorithm and FAST program, a time-domain coupled calculation ...model for a floating wind turbine is established, and a combined optimization design method for the wind turbine’s blade is developed in this paper. The influence of waves on the power of the floating wind turbine is studied in this paper. The results show that, with the increase of wave height, the power fluctuation of the wind turbine increases and the average power of the wind turbine decreases. With the increase of wave period, the power oscillation amplitude of the wind turbine increases, and the power of the wind turbine at equilibrium position decreases. The optimal design of the offshore floating wind turbine blade under different wind speeds is carried out. The results show that the optimum effect of the blades is more obvious at low and mid-low wind speeds than at rated wind speeds. Considering the actual wind direction distribution in the sea area, the maximum power of the wind turbine can be increased by 3.8% after weighted optimization, and the chord length and the twist angle of the blade are reduced.
This study analyzes the hydrodynamic performance and application of a pitching float-type wave energy conversion device under complex sea conditions in the South China Sea. Potential flow theory and ...ANSYS-AQWA software are used to establish a method for analyzing hydrodynamic performance in both time and frequency domains, as well as the various factors that influence hydrodynamic performance. The frequency domain characteristics of the conversion device are explored, as well as the time-domain characteristics when exposed to regular and irregular waves. The results show that the frequency domain of hydrodynamic performance conforms to the requirements of an offshore mobile platform. A mooring point that is closer to the center of mass leads to improved stability of the conversion device. The angle arrangement of the anchor-chain mooring method fully conforms to safety requirements. When the wave direction is 45°, the conversion device is highly stressed and its movement is the most strenuous; however, the device can operate safely and stably under all working conditions. These results provide a significant reference for expanding the wave-energy capture range and the hydrodynamic performance of floating wave-energy conversion devices.
Photocatalytic reduction of heavy metal ions is a green and promising technology which requires electrons with enough negative energy levels as well as efficient separation property from ...photo-generated holes of photocatalysts. For WO3, the low conduction band edge and the severe photo-generated charge carrier recombination limited its application in photocatalytic reduction of pollutants. In this work, we prepared WO3@PVP with PVP capped WO3 by a simple one-step hydrothermal method, which showed an elevated energy band structure and improved charge carrier separation property. XRD, SEM, TEM, XPS, DRS, and the photocurrent density test were carried out to study the properties of the composite. Results demonstrated monoclinic WO3 with a size of ∼100–250 nm capped by PVP was obtained, which possessed fewer lattice defects inside but more defects (W5+) on the surface. Moreover, the results of the photocatalytic experiment showed the kinetic constant of Cr(VI) reduction process on WO3@PVP was 0.532 h−1, which was 3.1 times higher than that on WO3 (0.174 h−1), demonstrating WO3@PVP with good photocatalytic capability for Cr(VI) reduction. This can be attributed to the improved charge carrier separation performance, the improved adsorption capacity and the elevated conduction band edge of WO3@PVP. More importantly, the energy band structure of WO3@PVP was proved elevated with a value as high as 1.14 eV than that of WO3 nanoparticles, which enables WO3@PVP a promising material in the photocatalytic reduction reaction of heavy metal ions from wastewater.
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•The conduction band edge of WO3@PVP was elevated by 1.14 eV than that of WO3.•WO3@PVP showed improved photocurrent density and adsorption capacity than WO3.•The reduction rate of Cr(VI) on WO3@PVP was 3.1 times higher than that on WO3.
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