For a narrow-brand seismograph with a flat response range limited, it cannot precisely record the signal of a ground motion and output the records with the low-frequency components cut down. A ...transfer function is usually used to spread the spectrum of the narrow-brand seismic records. However, the accuracy of the commonly used transfer function is not high. The authors derive a new transfer function based on the Laplace transform, bilinear transform, and Nyquist sampling theory to solve this problem. And then, the derived transfer function is used to correct the narrow-band velocity records from the Hi-net. The corrected velocity records are compared with the velocities integrated from the synchronously recorded broad-band acceleration at the same station with Hi-net. Meanwhile, the corrected records are compared with those corrected by the Nakata transfer function. The results show that the calculation accuracy of the derived transfer function is higher than the Nakata transfer function. However, when the signal-to-noise ratio is below 24, its accuracy diminishes, and it is unable to recover signals within the 0.05-0.78Hz frequency band.
To address the problem of large deformations in weak surrounding rock tunnels under high ground stress, which cause damage to initial support structures, this study proposes a novel type of ...circumferential pressure-relief joint based on the concept of relieving deformation pressure of the surrounding rock. Key parameters of the pressure-relief joint, such as initial bearing capacity peak, constant bearing capacity, and allowable pressure-relief displacement, were obtained through numerical simulations and laboratory experiments. A comparison was made between the mechanical characteristics of rigid joints and the new type of pressure-relief joint. The applicability of the pressure-relief joint was verified through field tests, monitoring the surrounding rock pressure, internal forces in the steel frames, and the convergence displacement of the support structure. The results show that: (1) In the elastic stage, the stiffness of the new pressure-relief joint is similar to that of rigid joints. In the plastic stage, rigid joints fail directly, whereas the pressure-relief joint can control deformation and effectively release the deformation pressure of the surrounding rock while providing a constant bearing capacity. (2) The right arch foot in the experiment had poor rock quality, leading to high stress in the steel frame and significant horizontal displacement. After the deformation of the pressure-relief joint, the stress in the surrounding rock and steel frame significantly reduced, and the rate of horizontal deformation of the support structure slowed down. (3) The vertical and horizontal final displacements of the pressure-relief joint in the experiment were 61mm and 15mm, respectively, which did not exceed the allowable deformation values. The components of the support structure remained intact, ensuring safety. However, this study has limitations: the design of the new pressure-relief joint only allows for a vertical deformation of 150mm and a horizontal deformation of 50mm, limiting the range of pressure-relief deformation.
•The effect of temperature on inhibition efficiency was investigated by experiments.•The interaction between SCMC and calcite was explored by MD.•The scale inhibition efficiency increases with the ...solution temperature.•The highest scale inhibition efficiency at 96.2% at 323 K.•The computational results agree with the anti-scaling experimental phenomena.
Sodium carboxymethyl cellulose (SCMC) is one of the most promising scale inhibitors. In this study, the performance of SCMC in inhibiting the deposition of calcium carbonate on heat transfer surface at the temperatures ranging from 293 to 343 K was investigated by experiments, and the interaction between SCMC and calcite in the solution was explored by molecular dynamics simulation. The experimental results showed that the fouling resistance substantially decreases by adding the SCMC. The scale inhibition efficiency increases with the solution temperature, and the highest scale inhibition efficiency at 99.8% at 343 K. The simulated results showed that with the increase of the solution temperature, both the binding energy between SCMC and calcite plane and the probability of SCMC binding with calcium ions increase, which can effectively prevent the growth of calcium carbonate fouling on the heat transfer surface. Therefore, our computational results agree with the anti-scaling experimental phenomena.
•HCE-SSPCM was prepared and used in under-floor heating system.•Enhancing thermal conductivity improved the efficiency of energy and space.•Too high thermal conductivity over a range was ...meaningless.•The economic benefits of the phase change energy storage system were the best.
A kind of heat conduction-enhanced shape-stabilized PCM (HCE-SSPCM) was utilized in the under-floor heating system for house heating in winter. This system charges heat by using cheap nighttime electricity and provides heating needs throughout all day. The effect of thermal conductivity of the PCM on energy savings and economic benefits of the system were theoretically and experimentally studied. HCE-SSPCM plates, made of (solid paraffin+liquid paraffin)/high density polyethylene/expanded graphite, were introduced to a test room with under-floor heating system. And the operating characteristics of the system were compared with that of the non-phase change energy storage system and the conventional air conditioning system. The results showed that enhancing the thermal conductivity of PCM in a certain range could significantly improve the energy efficiency of the heating system and reduce the thickness of thermal insulating materials. But the improving effect was not obvious when the thermal conductivity was beyond 1.0W/mK. The phase change energy storage system had a comfortable temperature environment and the best economic benefits among the three different heating types especially when the ratio of peak-valley electric price was high. Therefore, increasing the thermal conductivity of SSPCM will be of great significance for house heating.
•An integrated Eulerian model for fouling in turbulent flow was developed to simulate the particulate fouling characteristics.•The model comprises a deposition process and removal process and ...considers various factors affecting the particle deposition.•The important parameters are calculated and extracted by the User-defined function (UDF) code.•The model was applied to predict particulate fouling on the heat transfer surface in two real cases.•The simulation results obtained from the model in the two cases agrees well with published experimental data.
In this work, an integrated Eulerian model for fouling in turbulent flow was developed to simulate the particulate fouling characteristics. The model comprises a deposition process and removal process and considers various factors affecting the particle deposition, such as Brownian and eddy diffusion, gravity deposition, thermophoresis, and turbophoretic deposition. Several important parameters are calculated and extracted directly from the computational fluid dynamics model by the code, instead of relying on empirical formulas. The model was applied to predict particulate fouling in two experimental cases: particulate fouling on the surface of ventilation ducts and asphaltene fouling on the heat transfer surface in oil transport pipelines. The results show that the deposition rate obtained from the model in the two cases agree well with published experimental data. Furthermore, for the case of asphaltene fouling, at the early stage of fouling generation, the mass of asphaltene deposit on the surface also agrees well with the experimental results.
Steel slag (SS) has been largely discharged but little utilized, causing an environmental problem in China. In this paper, SS-based composite cementitious materials with high strength were prepared ...by the high volume of SS (≥40%), granulated blast-furnace slag (GBFS), fly ash (FA), flue gas desulfurization gypsum (FGDG) and cement to promote the effective utilization of SS. The hydration and hardening properties were studied through setting time, compressive strength, length change, isothermal calorimetry (IC), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) tests. The results show that SS-based composite cementitious material exhibited a lower hydration heat release, an appropriate setting time, and volume stability. The SS cementitious material with 40% SS could obtain high strength of over 65 MPa at 28 days and 80 MPa at 90 days. The strength value of > 60 MPa is present in the binder, with 50% SS at 56 days. GBFS promotes hydration reactions and the formation of AFt and C-(A)-S-H gel, thus enhancing compressive strength. FA has a beneficial effect on later strength. The small and fine pore structures contribute to the development of strength. The main hydration products of SS composite cementitious materials are C-(A)-S-H gel, and ettringite (AFt), with less Ca(OH)
. The C-(A)-S-H gel with a lower Ca/Si ratio and a higher Al/Ca ratio in cementitious material, promotes mechanical properties.
In this study, a novel low NOx burner is proposed and tested on a 40 MW pilot pulverized coal combustion system, aiming to experimentally investigate the impact of preheating temperature, air ratio ...distribution, and thermal power on furnace combustion characteristics. The experimental results demonstrate that the pulverized coal could be preheated stably above 700 °C in the designed burner. Furthermore, an increase in preheating temperature from 500 °C to 750 °C corresponds to a proportional rise in the total volume fraction of combustible pyrolysis gases released from pulverized coal, ranging from 18.34 % to 22.85 %. Consequently, the release and combustion of pyrolysis gases effectively improve the combustion characteristics within the boiler furnace and lead to reduced NOx emissions at the furnace outlet. When the thermal power is increased from 22.5 MW to 37.5 MW, the NOx emissions at the furnace output range from 46.8 mg/Nm3 to 98.3 mg/Nm3 (at 9 % O2). Under a specific thermal power of 25MWth, the boiler furnace output NOx emissions are reduced to 47.9 mg/Nm3 (@9 % O2) without any additional NOx reduction equipment. These findings offer valuable insights for advancing cleaner and more efficient low-NOx pulverized coal combustion technology.
•Low NOx technology for coal-fired boiler: a novel internal combustion burner.•NOx reduction path analysis combined with prepyrolysis treatment and air staging.•Impact of prepyrolysis temperature and air ratio on NOx emissions was studied.•Applicability for achieving ultra-low NOx emissions without SCR system.
With the rapid development of Telematics, Vehicle Self-Organizing Networks (VANETs) play an increasingly critical role in Intelligent Transportation Systems (ITS). Especially in the environment ...without roadside assistance units (RSUs), how to effectively manage inter-vehicle communication and improve the stability and communication efficiency of the network has become a hot topic of current research. In this paper, a Deep Reinforcement Learning-based Intelligent QoS-optimized efficient routing algorithm for vehicular networks (DRLIQ) is proposed for VANETs with/without RSU environments, and routing methods are proposed respectively. Among them, in RSU-free environment, the DRLIQ algorithm utilizes the powerful processing capability of deep reinforcement learning to intelligently select the optimal data transmission path by dynamically learning and adapting to the changes in the vehicular network, thus effectively reducing communication interruptions and delays, and improving the accuracy of data transmission. The performance of the DRLIQ algorithm under different vehicle densities is evaluated in simulation experiments and compared with current popular algorithms. The experimental results show that the DRLIQ algorithm outperforms the comparison algorithms in reducing the number of communication interruptions, BER and network delay, especially in vehicle-dense environments. In addition, the DRLIQ algorithm shows higher adaptability and stability in coping with network topology changes and vehicle dynamics.
The efficiency of photovoltaic(PV) panels decreases as their temperature increases, so effective cooling of them is necessary. The cooling of PV panels based on phase change materials(PCMs) is an ...emerging cooling method that has recently received the attention of scholars around the world. Herein, the cooling characteristics of PCM on PV panels are experimentally investigated to study the cooling effect of PCM on solar PV panel cooling technology (PV-PCM) and explore the effect of inverse process of PCM from molten to solidified state on the temperature of solar PV panels after cooling. The results reveal that the PCM can effectively reduce the temperature of solar PV panels under the condition of no wind, irradiance of 1000 W/m2 and ambient temperature of 7.3 °C. The PCM can reduce the average temperature of the upper and back surfaces of solar PV panels by 33.94 °C and 36.51 °C within 300 min, respectively. Moreover, the PCM increased the average maximum power generation efficiency of solar PV panels by 1.63% and the average maximum output power by 1.35 W. The solar PV panels cooled without PCM took only 60 min to cool from the maximum temperature to room temperature, whereas the solar PV panels in PV-PCM system took 480 min to cool down to room temperature.
Passive radar based on the global navigation satellite positioning system (GNSS) has become the focus of attention in the field of radar. A parameter estimation method is proposed in the forward ...scatter radar (FSR) network based on GNSS to extend the application scenarios. For uniformly accelerating moving targets, only the instant times when the target crosses the individual baselines are used to retrieve the target motion parameters. The target position, velocity, and acceleration information can be obtained. Firstly, the minimum network configuration is derived theoretically. Then, the effects of crossing time error, station location error, transmitting/receiving station deployment, and target height on the accuracy are analyzed through Monte Carlo simulations. Finally, the simulation results indicate that the target position estimation error is in the order of 100 m. This paper provides the fundamental theory of aerial target positioning with a GNSS-based FSR network.
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