•A method named Injected Fresh Air was proposed.•In-cylinder swirl ratio was improved with the IFA strategy.•Fuel/air mixing and combustion process were optimized with the IFA strategy.•IFA strategy ...showed a good performance on NOx emission and BSFC under EGR atmosphere.
Exhaust Gas Recirculation (EGR) is one of the most effective in-cylinder NOx emission reduction methods to meet the Tier III standards, but the introduction of the exhaust gas is usually accompanied by the expense of fuel economy. To solve the deterioration of fuel economy when using EGR, a method named Injected Fresh Air was firstly proposed to improve the swirl level of in-cylinder flow without sacrificing the scavenging efficiency in this work. The related numerical research of the fuel/air mixing process, combustion performance and emission characteristics on the EX340EF two-stroke low-speed marine engine at 75% load under EGR atmosphere was performed. With the IFA strategy under EGR atmosphere, the swirl ratio could increase by 163%, accelerating the fuel/air mixing process and further optimizing subsequent combustion performance. As a result, compared with the cases without the IFA strategy at the EGR rate of 20%, 25%, and 30%, the duration of CA90 with the IFA strategy was reduced by 47.1%, 49.4% and 50.8%, respectively, and both the NOx emission and the brake specific fuel consumption (BSFC) were decreased. Finally, compared with the base case, the NOx emission was reduced to 2.82 g/kWh with a nearly 75.5% reduction when using the IFA strategy under the EGR rate of 40%, which could meet the Tier III standards (3.4 g/kWh). Moreover, the BSFC was decreased by 2.33 g/kWh with a nearly 1.3% reduction. The IFA strategy successfully achieved the goal of improving the fuel/air mixing and combustion process under EGR atmosphere by enhanced swirl ratio, and the results of this study can be used to develop a new method to satisfy the IMO Tier III requirements and avoid high fuel consumption, has a better application prospect in emissions control and fuel consumption optimization of low-speed two-stroke diesel marine engines.
Highlights
A novel windmill-like hybrid nanogenerator with contact-separation structure was proposed for harvesting breeze energy at low wind speed.
A spring steel sheet was creatively used both as ...an electrode of triboelectric nanogenerator and a booster for contact-separation activity.
A magnetic acting as a bifunctional element supplies magnetic flux variation in electromagnetic generator and overcomes electrostatic adsorption between tribolayers simultaneously.
Wind energy is one of the most promising and renewable energy sources; however, owing to the limitations of device structures, collecting low-speed wind energy by triboelectric nanogenerators (TENGs) is still a huge challenge. To solve this problem, an ultra-durable and highly efficient windmill-like hybrid nanogenerator (W-HNG) is developed. Herein, the W-HNG composes coupled TENG and electromagnetic generator (EMG) and adopts a rotational contact-separation mode. This unique design efficiently avoids the wear of friction materials and ensures a prolonged service life. Moreover, the generator group is separated from the wind-driven part, which successfully prevents rotation resistance induced by the friction between rotor and stator in the conventional structures, and realizes low-speed wind energy harvesting. Additionally, the output characteristics of TENG can be complementary to the different performance advantages of EMG to achieve a satisfactory power production. The device is successfully driven when the wind speed is 1.8 m s
−1
, and the output power of TENG and EMG can achieve 0.95 and 3.7 mW, respectively. After power management, the W-HNG has been successfully applied as a power source for electronic devices. This work provides a simple, reliable, and durable device for improved performance toward large-scale low-speed breeze energy harvesting.
Sensitive and accurate quantification of circulating tumor cell (CTC) can provide new insights for early diagnosis and prognosis of cancers. Herein, we have developed a multipedal DNA walker for ...ultrasensitive detection of CTC for the first time. Generally, a number of walker strands are simply modified on gold nanoparticle (AuNPs). The integrated aptamer sequence can specially interact with the transmembrane receptor protein of CTC and facilitate the enrichment of AuNPs on the surface of cells. After a low speed centrifugation, the complex of CTC and AuNPs could be precipitated and the supernate represents decreased UV–vis absorbance response of AuNPs. On the other hand, since multiple walker strands are modified on a single AuNP, hybridization with several tracks on the electrode occurs simultaneously for the following nicking endonuclease-catalyzed cleaving. Experimental results verify that the rate of multipedal walking is much faster. In addition, TCEP-mediated electrochemical amplification is employed to further enhance the electrochemical signal. By comparing the variations of electrochemical and UV–vis absorbance responses, ultrahigh sensitivity for CTC assay is achieved. The limit of detection is down to 1 cell/mL. The results of selectivity confirmation and blood sample test are also satisfactory. This AuNPs-based multipedal DNA walker offers a speedy analysis of CTC and shows great potential use for early clinical diagnosis and treatment of cancers.
The rapid growth of the consumer Internet of Things (CIoT) has resulted in substantial enhancements in networking and data analytics. The emergence of customer-centric communication technologies like ...mobile ad hoc networks (MANETs) and vehicular ad hoc networks (VANETs), also known as self-organizing networks (SONs), along with the integration of 5G Internet of Things and artificial intelligence, has paved the way for intelligent transportation systems (ITS). In SONs, each vehicle serves as a network node. Hence, it is essential for these network nodes to interact, communicate, and exchange data in a flexible, efficient, and convenient manner. SONs offer revolutionary communication capabilities by enabling self-configuration, self-setting, and autonomous data transmission. However, one significant drawback of SONs is their poor network performance. In this study, we have developed an efficient routing scheme that aims to enhance the performance and reduce energy consumption of SONs for ITS in smart cities with low mobility speeds. The simulation results clearly show that the proposed algorithm performs better than conventional routing protocols in low-speed mobility scenarios. It outperforms in terms of network lifetime, packet delivery ratio, and latency.
Abstract
In order to study the sequential turbocharging switching process of low-speed diesel engine, this paper uses GT-power software to establish a simulation model of sequential turbocharging ...low-speed diesel engine. It is enhanced and improved into a model of a sequential supercharged diesel engine. Modules such as load, governor, valve control, and surge margin are set up in the simulation model. Then parameters such as switching speed, valve opening time and response time are set in the model. Through the above preparations, the thesis has carried out the simulation calculation of the sequential supercharging transient switching process and verified the rationality of the setting parameters and the accuracy of the module setting. This provides a certain reference for the valve control strategy of the sequential supercharging switching system of low-speed diesel engines.
Additive manufacturing (AM) enables the design and fabrication of foams with intricate cell architectures for enhanced mechanical performances in blast and impact mitigation applications. Although ...the crushing response of AM foams has been studied recently, there is limited research on their failure behaviours under dynamic loading. This work investigates the response of AM Voronoi foams under compressive loadings through a combined experimental and numerical effort, with the emphasis on the failure behaviour and its modelling. Voronoi foams with uniform and graded density distributions were fabricated via the Fused Deposition Modeling technique. Quasi-static (0.001 s−1) and low-speed impact (50 s−1) tests were carried out to quantify the mechanical response and to characterise the deformation and failure behaviours. Computational models of the Voronoi foams were built in ABAQUS and validated with the experiment to provide insights into the dynamic fracture behaviours. Results showed that although failure plays a minor role in the quasi-static loading case, dynamic compressive loading can yield complex fracture behaviours involving cell-wall buckling, cell-wall rupturing, large-scale shattering and shear band localisation, resulting in significant stress softening and strong stress fluctuations during the post-yield response. Consequently, the load-bearing and energy absorbing capacities materially deteriorated when transiting from quasi-static to dynamic loading conditions. The results reported in this work provide valuable guidance on the design of AM foams under dynamic loadings.
•Deformation and failure of AM Voronoi foams are characterised and modelled.•Failure plays a minor role in quasi-static loading, but strongly dictates the structural response in dynamic loadings.•Dynamic loaded foams display complex fracture behaviours.•Strong stress softening and oscillation are observed in the post-yield buckling in the presence of structural failure.
Abstract
Brake pads and brake shoes are the main components of the friction pair of the subway air brake. At present, the average coefficient of friction is usually used as a criterion for evaluating ...the braking effect of pads and shoes. In this paper, by analyzing the braking process of the subway, it is inferred that the average friction coefficient has a poor evaluation effect under the low-speed common braking conditions, and a new alternative evaluation index, the equivalent average friction coefficient at low speed, is proposed. The conjecture is verified by the test bench test, and the feasibility of the low-speed equivalent average friction coefficient as an evaluation index under low-speed conditions is proved.
This paper presents a new application of the largest Lyapunov exponent (LLE) algorithm for feature extraction method in low speed slew bearing condition monitoring. The LLE algorithm is employed to ...measure the degree of non-linearity of the vibration signal which is not easily monitored by existing methods. The method is able to detect changes in the condition of the bearing and demonstrates better tracking of the progressive deterioration of the bearing during the 139 measurement days than comparable methods such as the time domain feature methods based on root mean square (RMS), skewness and kurtosis extraction from the raw vibration signal and also better than extracting similar features from selected intrinsic mode functions (IMFs) of the empirical mode decomposition (EMD) result. The application of the method is demonstrated with laboratory slew bearing vibration data and industrial bearing data from a coal bridge reclaimer used in a local steel mill.
•This paper presents a new application of the largest Lyapunov exponent (LLE) algorithm for feature extraction.•The increase deterioration level of slew bearing is detected.•The comparison between LLE feature and time-domain features and EMD is reported.•The most important LLE parameters namely reconstruction delay J is selected based on the FFT.
The triboelectric nanogenerator (TENG) is an emerging technology for ambient mechanical energy harvesting, which provides a possibility to realize wild environment monitoring by self‐powered sensing ...systems. However, TENGs are limited in some practical applications as a result of their low output performance (low charge density) and mechanical durability (material abrasion). Herein, an ultrarobust and high‐performance rotational TENG enabled by automatic mode switching (contact mode at low speed and noncontact at high speed) and charge excitation is proposed. It displays excellent stability, maintaining 94% electrical output after 72 000 cycles, much higher than that of the normal contact‐mode TENG (30%). Due to its high electrical stability and large electrical output, this TENG powers 944 green light‐emitting diodes to brightness in series. Furthermore, by harvesting water‐flow energy, various commercial capacitors can be charged quickly, and a self‐powered fire alarm and self‐powered temperature and humidity detection are realized. This work provides an ideal scheme for enhancing the mechanical durability, broadening the range of working frequency, and improving the electrical output of TENGs. In addition, the high‐performance hydrodynamic TENG demonstrated in this work will have great applications for Internet of Things in remote areas.
A charge excitation and automatic mode switching triboelectric nanogenerator (TENG) is proposed, which displays outstanding durability and electrical output at the same time. This work provides an ideal scheme for enhancing the mechanical durability and broadening the range of working frequency as well as improving the electrical output performance of TENGs.
The magnetic suspension system of a low-speed maglev train is presented in this paper. The design and realization of the magnetic suspension controller are discussed, and a nonlinear mathematical ...model of the magnetic suspension system is built. Then, the proportion integration differentiation controller is investigated, which indicates that it is sensitive to disturbances. To reject the disturbance and parameter perturbations, an adaptive neural-fuzzy sliding mode controller is presented, which employs a sliding mode control, adaptive-fuzzy approximator, and the neural-fuzzy switching law. The sufficient simulation and experimental results are included to demonstrate that the presented robust controller significantly reduces the impact of the disturbance and parameter perturbations with a smooth control current.
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