bluuebunny/crossref_metadata_2025 huggingface dataset:
Mantle‐Derived Helium and Multiple Methane Sources in Gas Bubbles of Cold Seeps Along the Cascadia Continental Margin
Authors: Baumberger Tamara , Embley Robert W. , Merle Susan G. , Lilley Marvin D. , Raineault Nicole A. , Lupton John E.
Published: October 2018

During E/V Nautilus NA072 expedition, multibeam sonar surveys located over 800 individual bubble streams rising from the Cascadia Margin between the Strait of Juan de Fuca and Cape Mendocino at depths between 104 and 2,073 m. Gas bubbles were collected directly at the seafloor using gastight sampling bottles. These bubbles were consistently composed of over 99% methane with traces of carbon dioxide, oxygen, nitrogen, noble gases, and more rarely higher hydrocarbons. A common previous view was that a biogenic source was responsible for seeps from within the gas hydrate stability zone (upper limit near 500‐m isobath) and a thermogenic source was responsible for seeps from the upper slope and the shelf. Higher hydrocarbons in deep seeps with a biogenic methane signature, as well as the lack of higher hydrocarbons in some shallower seeps with a thermogenic methane signature, show that the origin of the gas cannot simply be attributed to seep location on the margin. Instead, mixing and oxidation processes play an integral role. 3He/4He ratios at Coquille SW point to a contribution of 30% mantle helium, whereas all the other investigated sites are characterized by a crustal helium signature. Hence, the Coquille SW seeps are directly or indirectly connected to the mantle or to very young oceanic crust. The detection of mantle helium in these seeps can thus be used as a tracer for deep‐reaching fracture systems and their changing pathways.
The Volume of Gas Hydrate‐Bound Gas in the Northern Gulf of Mexico
Authors: Majumdar Urmi , Cook Ann E.
Published: October 2018

The northern Gulf of Mexico is known to host gas hydrate in submarine sediments. Estimating the amount of gas hydrate for both carbon cycle and resource interest has been ongoing for more than three decades. A large range of estimates (from 0.2 to 680 trillion cubic meters (TCM)) for hydrate‐bound natural gas at standard temperature and pressure exists. We bring a new perspective to resource estimates by using ~800 publicly available petroleum industry well logs assessed for natural gas hydrate. Our resulting probabilistic range of the gas hydrate‐bound natural gas in the northern Gulf of Mexico ranges from 37 TCM (10th percentile estimate) to 78 TCM (90th percentile estimate) of gas hydrate‐bound natural gas, with a mean estimate of 56 TCM. This suggests that the gas hydrate resource density of the northern Gulf of Mexico is 4 times lower than that previously estimated by the Bureau of Ocean Energy Management. Our results also indicate that over half of the gas hydrate in the area is strategically hosted in sand reservoirs, which is significantly higher than that previously estimated.
The Calcium Isotope Systematics of the Late Quaternary Dead Sea Basin Lakes
Authors: Bradbury Harold J. , Torfstein Adi , Wong Kenneth , Turchyn Alexandra V.
Published: October 2018

We report the calcium isotopic composition (δ44Ca) of primary aragonite laminae, primary gypsum, and secondary gypsum in sediments deposited from Lake Lisan, the last glacial cycle of the Dead Sea (70–14.5 ka). The δ44Ca of primary gypsum varies between 0.17‰ and 0.71‰ versus bulk silicate earth, with an average of 0.29‰, whereas the aragonite δ44Ca varies between −0.68‰ and −0.16‰ with an average of −0.4‰. The secondary gypsum δ44Ca is close to the calcium isotope composition of the aragonite, averaging at −0.3‰. The aragonite δ44Ca shows small variations temporally in sync with lake level fluctuations, suggesting the aragonite δ44Ca reflects changes in the lake calcium balance, which in turn reflects changes in the local hydrological cycle. The secondary gypsum calcium isotope composition (−0.3‰) overlaps with that of coeval aragonite, suggesting the calcium for secondary gypsum was derived from the aragonite through quantitative, or near‐isotopic equilibrium, recrystallization of the aragonite to gypsum after the lake desiccation and exposure of sediments during the Holocene. A numerical box model is used to explore the effect of changing lake water levels on the calcium isotope composition of the aragonite and gypsum in the lake. The relatively low variability in the δ44Ca over the lake's history suggests that a high‐concentration calcium‐rich brine buffers the calcium cycle.
Combined Effects of Gametogenic Calcification and Dissolution on δ18O Measurements of the Planktic Foraminifer Trilobatus sacculifer
Authors: Wycech Jody B. , Kelly Daniel Clay , Kitajima Kouki , Kozdon Reinhard , Orland Ian J. , Valley John W.
Published: October 2018

Oxygen isotope ratios (δ18O) measured from planktic foraminifer shells are commonly used to reconstruct past surface ocean conditions, yet the shells of many planktic foraminifers are an aggregate mixture of multiple carbonate phases with differing δ18O compositions. Here we demonstrate how secondary ion mass spectrometry can be used to measure intrashell δ18O heterogeneity by performing in situ analyses on micrometer‐scale (3–10 μm) domains within individual shells of the extant, mixed layer species Trilobatus sacculifer. Secondary ion mass spectrometry measurements on shells taken from Holocene‐aged sediments at three sites in different ocean basins confirm that the δ18O of gametogenic (GAM) calcite added to shells during the terminal (reproductive) stage of the life cycle is 1.0–1.4‰ higher than that of pregametogenic calcite. Examination of shells in cross section reveals that many have suffered varying degrees of internal dissolution, which further skews whole‐shell δ18O compositions toward higher values by preferentially removing low δ18O pregametogenic calcite. The results of this study echo the calls of earlier studies cautioning that spatiotemporal changes in the proportion of high δ18O GAM calcite should be considered when assessing T. sacculifer δ18O records generated via conventional isotope ratio mass spectrometry.
Satellite‐Based Estimation of Particulate Organic Carbon Export in the Northern South China Sea
Authors: Li Teng , Bai Yan , He Xianqiang , Xie Yuyuan , Chen Xiaoyan , Gong Fang , Pan Delu
Published: October 2018

Knowledge of particulate organic carbon export flux (EP) is the key to understanding the marine biological carbon pump. In this study, a satellite remote sensing algorithm based on the food‐web model established by Siegel et al. (2014; https://doi.org/10.1002/2013GB004743) was used to estimate EP in the northern South China Sea (NSCS), which consists of direct sinking flux of large phytoplankton and associated aggregates by gravity and flux of zooplankton feces by grazing. This is the first time that fine spatiotemporal variation of satellite‐derived EP in the NSCS is unveiled. Compared with the results on 1° spatial scale products, the model results based on the satellite products with 1/3° and 1/12° resolutions showed better consistency with the observations. Validation with in situ EP showed that the model exhibited a good performance in the NSCS basin, but the predicted EP in the shelf regions were smaller compared with measurements. The satellite‐derived annual‐mean EP in the shelf areas was 8.47 and 5.56 mmol C·m−2·d−1 in the NSCS basin, on the 1/3° spatial scale, with relative differences from observations were about −50% and −15% for the shelf and basin, respectively. The flux of feces from zooplankton grazing, especially that from microzooplankton grazing, might account for the major fraction of the EP in the NSCS. Accurate products of ocean net primary production and empirical coefficients in the food web (e.g., export efficiency of zooplankton grazing and specific mortality rate of nongrazing phytoplankton) suitable for the NSCS, are essential for performance improvement of the satellite‐based EP model.
Low‐Cloud Feedback in CAM5‐CLUBB: Physical Mechanisms and Parameter Sensitivity Analysis
Authors: Zhang Haipeng , Wang Minghuai , Guo Zhun , Zhou Chen , Zhou Tianjun , Qian Yun , Larson Vincent E. , Ghan Steven , Ovchinnikov Mikhail , Bogenschutz Peter A. , Gettelman Andrew
Published: October 2018

The physical mechanism of low‐cloud feedbacks is examined by using perturbed‐parameter ensemble experiments in a unified scheme of boundary layer turbulence and shallow convection, named Cloud Layers Unified by Binormals (CLUBB) coupled to Community Atmosphere Model version 5 (CAM5). The shortwave cloud feedbacks in CAM5‐CLUBB are positive in the most stable tropical regime, which is related to the weaker turbulence in the planetary boundary layer (PBL) in a warmer climate that is possibly triggered by the strengthened stability of the cloud layer. The positive feedback between low cloud cover (LCC), cloud top radiative cooling, and PBL turbulent mixing may further enhance the decrease in LCC. The stronger inversion stability of PBL partly counters the decrease in LCC, and a recently developed index, the estimated cloud‐top entrainment index, is a better predictor for LCC changes than conventional stability indices. The relative strength of shallow convection increases in the warmer climate, but its effect on low‐cloud feedback is complicated by the unified treatment of shallow convection and PBL turbulence in CLUBB. Stronger shallow convection means more convective drying but also less PBL turbulence and less LCC in the present climate, which leads to less reduction in LCC. The parameters related to dynamic turbulent structure and double Gaussian closure in CLUBB are the most influential parameters on low‐cloud feedbacks. Our results suggest that a unified treatment of shallow convection and turbulence may give rise to the predominate role of the PBL turbulent mixing in determining low‐cloud feedback.
Mechanical, thermal, and electrochemical properties of Pr doped ceria from wafer curvature measurements
Authors: Ma Yuxi , Nicholas Jason D.
Published: October 2018

This work demonstrates, for the first time, that a variety of disparate and technologically-relevent thermal, mechanical, and electrochemical oxygen-exchange material properties can all be obtained from in situ, current-collector-free wafer curvature measurements.
Comparison of two multifunctional catalysts [M/Nb2O5 (M = Pd, Pt)] for one-pot hydrodeoxygenation of lignin
Authors: Dong Lin , Shao Yi , Han Xue , Liu Xiaohui , Xia Qineng , Parker Stewart F. , Cheng Yongqiang , Daemen Luke L. , Ramirez-Cuesta Anibal J. , Wang Yanqin , Yang Sihai
Published: October 2018

Improved lignin valorisation via its catalytic conversion to value-added feedstocks is of essential importance to the development of future bio-refineries.
A new method to discover the reaction mechanism of perovskite nanocrystals
Authors: Sun Chun , Gao Zhiyuan , Liu Hanxin , Geng Chong , Wu Hua , Zhang Xiaoyu , Fan Chao , Bi Wengang
Published: October 2018

A novel and simple method for revealing the reaction mechanism of perovskite nanocrystals is reported.
A biocompatible metal–organic framework as a pH and temperature dual-responsive drug carrier
Authors: Lin Wenxin , Cui Yuanjing , Yang Yu , Hu Quan , Qian Guodong
Published: October 2018

A biocompatible metal–organic framework Zn-GA comprising zinc ions and the bio-friendly molecule l-glutamic acid (GA) is synthesized as a drug delivery system, and controlled drug release triggered by pH and thermal stimuli without premature delivery is realized.
NiCo2O4/NiCoP nanoflake-nanowire arrays: a homogeneous hetero-structure for high performance asymmetric hybrid supercapacitors
Authors: Zong Quan , Yang Hui , Wang Qianqian , Zhang Qilong , Xu Jin , Zhu Yulu , Wang Huiying , Wang Hao , Zhang Fang , Shen Qianhong
Published: October 2018

Transition metal phosphides (TMPs) represent an important class of compounds with metalloid characteristics and good electrical conductivity, which are of great benefit to enhance electrochemical performances.
Mitochondria-targeting and cell-penetrating peptides-co-modified HPMA copolymers for enhancing therapeutic efficacy of α-tocopheryl succinate
Authors: Liu Yanxi , Li Qiuyi , Xiong Xiaofeng , Huang Yuan , Zhou Zhou
Published: October 2018

Targeting drugs at mitochondria may provide an effective means of inducing cell death for cancer therapy.
Metastable phase control of two-dimensional transition metal dichalcogenides on metal substrates
Authors: Ling Faling , Jing Huirong , Chen Yankun , Kang Wei , Zeng Wen , Liu Xiaoqing , Zhang Yixin , Fang Liang , Zhou Miao
Published: October 2018

Engineering the stability of the metastable phase of 2D MoS2by appropriate choice of metal substrate determined by the electron occupation of Mo d-orbitals.
Fast beam alignment algorithm for multi‐user mmWave communications
Authors: Zhang Renmin , Zhang Hua , Xu Wei
Published: October 2018

The training overhead in pursuing pencil beams is commonly heavy for millimetre‐wave (mmWave) communications, particularly in multi‐user (MU) scenarios with conventional sequential‐training methods. To reduce the training overhead, a parallel beam alignment algorithm is proposed for the MU mmWave system with a hybrid structure. The proposed algorithm jointly exploits parallel beam alignment among different user‐subsets and hierarchical beam training for each user‐subset. Consequently, the training overhead is significantly reduced to for the mmWave systems with transmit antennas. Numerical results verify that the proposed algorithm outperforms traditional alternatives in MU scenarios.
Performance difference between zero‐forcing and maximum likelihood detectors in massive MIMO systems
Authors: Minango J. , Altamirano C.D. , de Almeida C.
Published: October 2018

In massive multiple‐input multiple‐output (MIMO) systems with hundreds of antennas at the base station (BS) and few users with a single transmitter antenna, linear detectors, such as zero‐forcing (ZF), achieve near‐optimum performance due to the property of asymptotically orthogonal channel matrix. However, how far away is ZF from the optimum performance. To answer this question, in this Letter, closed‐form bit error rate (BER) expressions are derived. These BER expressions are subsequently used to evaluate the performance difference between ZF and the optimum detector, which is a function of the number of antennas at the BS and the number of users. Numerical results verify the tightness of the performance difference.
Energy harvesting two‐way relaying with antenna selection scheme
Authors: Noor‐A‐Rahim Md. , Khyam Mohammad Omar , Guan Yong Liang
Published: October 2018

This study investigates the performance of a bidirectional/two‐way relaying scheme with an energy‐harvesting relay while amplify‐and‐forward relaying is performed. With multiple antennas at the relay, the authors propose the use of the max–min antenna selection scheme in the context of an energy harvesting scenario. They show that the proposed scheme attains diversity gain, whereby its end‐to‐end symbol error probability performance improves with increments in the number of energy harvesting relay antennas. For limited battery capacity at the energy harvesting node, they derive the lower bound of the outage probabilities and observe a good match between the analytical and simulated results. For this scenario, a simple power provisioning technique is proposed to optimise the end nodes' transmission powers. It is observed that the proposed technique saves significantly more transmission energy than the conventional equal power provisioning technique.
Fault data injection attack on car‐following model and mitigation based on interval type‐2 fuzzy logic controller
Authors: Gunasekaran Prabhakar , Sundaramoorthy Selvaperumal , Pulikesi Nedumal Pugazhenthi
Published: October 2018

Cyber defence mechanism is started with modelling the accurate car‐following behaviour including cyber attack. The creation of finest models made the path of control action easier. The connection between the vehicles is mathematically formulated with the help of car‐following behaviour, incorporating the derived acceleration function from the cruise control physical system. The modified car‐following model is simulated as closed‐loop control system to analyse its behaviour in terms of acceleration and distance. Fault data injection cyber attack is mathematically injected into the modified car‐following model and simulated to analyse the impact of attack. Initially, the impact of fault data injection attack is detected and mitigated with the help of parallel proportional–integral–derivative controller and genetic algorithm tuned proportional–integral–derivative controller. Interval type‐2 fuzzy proportional–integral–derivative controller is introduced to mitigate the cyber attack and to overcome the uncertainty. The integral square error and integral absolute error are used to compare the performance of the controllers. Inbuilt Wi‐Fi connected car like mobile robots are used in real‐time model. This model is designed and developed based on the Node MCU processors, real‐time operating system, sensors and actuators.
Inflow and outflow stenoses screening on biophysical experimental arteriovenous graft using big spectral data and bidirectional associative memory machine learning model
Authors: Lin Chia‐Hung , Chen Wei‐Ling , Kan Chung‐Dann
Published: October 2018

Long‐term repeating traumatic puncture is required for dialysis therapy, which results in frequent thrombosis and graduate vascular access stenosis, such as inflow or outflow stenosis and coexistence of both. An arteriovenous graft has a higher patency rate than an arteriovenous fistula. This study intends to use the dual‐channel auscultation‐based non‐invasive method to screen inflow and outflow stenoses. Frequency analysis is used to decompose phonoangiography (PAG) signals to frequency features using the different data length of acoustic data. Burg autoregressive method is employed to extract the key frequency parameters from sufficient spectral data, including characteristic frequencies and distinct peaks of power spectral densities (PSDs). In big data processing, PSDs and the degree of stenosis (DOS) have been validated to show a positive correlation with sufficient big spectral data. An intelligent machine learning model, bidirectional hetero‐associative memory network (BHAMN), is carried out to identify the level of DOS at the inflow site, the mid‐site, or the outflow site of a vascular access. The experimental results will indicate that the proposed intelligent machine learning model has higher hit rates.
FARIMA model‐based communication traffic anomaly detection in intelligent electric power substations
Authors: Yang Qiang , Hao Weijie , Ge Leijiao , Ruan Wei , Chi Fujian
Published: October 2018

The technological advances of intelligent electric substations have significantly improved the operational performance of power utilities by incorporating advanced monitoring and control functionalities. The data traffic patterns in substation communication network (SCN) need to be better understood to improve the SCN performance against different forms of cyber‐attacks. To this end, this study presents a fractional auto‐regressive integrated moving average (FARIMA)‐based threshold model to characterise the SCN traffic flow based on the IEC 61850 protocol and carry out anomaly detection. The performance of the proposed anomaly detection solution is assessed and validated through numerical analysis under the condition of the cyber storm based on the collected SCN data traffic from a real 110 kV substation, and the numerical results clearly confirmed its effectiveness.
Performance validation of vehicle platooning through intelligible analytics
Authors: Mongelli Maurizio , Ferrari Enrico , Muselli Marco , Fermi Alessandro
Published: October 2018

The study deals with intelligible analytics for performance modelling of vehicle platooning. Knowledge extraction with rules is targeted to understand safety regions (collision avoidance) of system parameters. Results are shown by feeding data through simulation to the train of different rule extraction mechanisms. Safety regions are evidenced on test data with statistical error very close to zero.
Switching tracking control for linear time‐invariant systems without overshoot: a positive systems method
Authors: Zhang Yaoli , Zhao Jun
Published: October 2018

In this study, the authors study the issue of how to design controllers to asymptotically track a constant signal without overshoot for linear time‐invariant systems. Using the theory of positive systems, they obtain the non‐negative invariant set of the output for the autonomous systems. Then, a linear state feedback controller is designed to ensure the non‐overshooting tracking when the initial state is in some region. Furthermore, for a single‐input single‐output system, the problem of global non‐overshooting tracking control is solved by a switching control law. For multi‐input multi‐output systems, they also obtain the non‐overshooting response under some assumptions. A numerical example is given to illustrate the effectiveness of the proposed theory.
Self‐triggered robust model predictive control for nonlinear systems with bounded disturbances
Authors: Su Yanxu , Wang Qingling , Sun Changyin
Published: October 2018

A self‐triggered model predictive control (MPC) scheme for continuous‐time perturbed nonlinear systems subject to bounded disturbances is investigated in this study. A self‐triggered strategy is designed to obtain the inter‐execution time before the next trigger using the current sampled state. An optimisation problem is addressed to obtain the optimal control trajectory at each triggered instant. The so‐called dual‐mode approach is used to stabilise the perturbed closed‐loop system. Furthermore, sufficient conditions are derived to ensure the feasibility and stability, respectively. It is shown that with a properly designed prediction horizon, the feasibility of the proposed self‐triggered MPC algorithm can be guaranteed if the disturbance is bounded in a small enough area. Meanwhile, the stability is proved under the self‐triggered condition. Finally, a numerical example is given to illustrate the efficacy of the authors proposed scheme.
Design of controllers for hybrid linear systems with impulsive inputs and periodic jumps
Authors: Menini Laura , Possieri Corrado , Tornambè Antonio
Published: October 2018

In this study, the problem of designing a controller for a hybrid system with impulsive input and periodic jumps is addressed. In particular, it is shown that any hybrid system with impulsive inputs and periodic jumps can be recast into a discrete‐time, linear, time‐invariant system, which, in turn, can be used to design a controller by using classical methods. Furthermore, it is shown that, once such a controller has been designed, it can be readily used to control the hybrid system by mean of an interfacing system that is based just on the continuous‐time dynamics of the plant to be controlled. Several examples, spanning from aerospace to biomedical applications, are reported in order to corroborate the theoretical results.
Piecewise affine identification of a hydraulic pumping system using evolutionary computation
Authors: Barbosa Bruno H.G. , Aguirre Luis A. , Braga Antonio P.
Published: October 2018

Identification of piecewise affine hybrid systems is not an easy task since both the parameters determining the discrete modes and the submodels parameters have to be obtained, leading to a non‐convex combinatorial optimisation problem. One way around this problem is to solve it in two steps. This work presents an approach for simultaneously estimating the parameters for PieceWise Autoregressive eXogeneous and PieceWise Output Error models. This is accomplished by using evolutionary algorithms for finding the parameters of the discrete modes (Gaussian mixture models) and employing the proposed weighted and extended least squares algorithm to estimate the ARX or ARMAX submodels. The main advantages of the proposed algorithm are: (i) it can be applied to output error models – which correspond to system with measurement noise, (ii) it is less likely to get trapped in local minima and (iii) it is applicable to problems with large datasets. The proposed approach, which is offline, was validated using simulated and experimental data and was compared with another method from the literature. In the case of an experimental plant, parsimonious models with good performance in both dynamic and static regimes were obtained.
Hybrid filter design of fault detection for networked linear systems with variable packet dropout rate
Authors: Wang Dongzhe , Mei Xueheng , Weng Rui , Qu Zhenshen , Zhang Lixian
Published: October 2018

The study focuses on the fault detection filter design problem for a class of networked systems with intermittent measurements. The fault detection filter, which is used as residual generator, is formulated as an filtering form. The random packet dropouts are governed by a Bernoulli distributed sequence, and the packet dropout rate is uncertain and variable, which is described by a semi‐Markov stochastic process. A more general class of Lyapunov functions that not only depend on the system modes, but also on the staying time during the current system mode is utilised. Afterwards, numerically testable sufficient conditions on the existence of a desired fault detection filter are established such that the filtering error system is ‐error mean square stable with a prescribed disturbance attenuation level. Finally, an illustrative example is provided not only to demonstrate the effectiveness of the designed filter and the superiority of the utilisation of semi‐Markov chain, but also the necessity of considering the variation of packet dropout rate in the design phase.
Decoupling start control method for aircraft wound‐rotor synchronous starter‐generator based on main field current estimation
Authors: Jiao Ningfei , Liu Weiguo , Meng Tao , Sun Chenghao , Jiang Yu
Published: October 2018

Wound‐rotor synchronous starter‐generator (WRSSG) has the advantages of less volume and weight, high safety and low cost in maintenance, so it is becoming increasingly popular in modern aircraft, especially for more‐electric aircraft. The main machine (MM) and main exciter (ME) of the aircraft WRSSG are electromechanically coupled seriously, which makes the start control for the WRSSG complex in the starting mode. In this study, a decoupling start control method for aircraft WRSSG based on main field current estimation is proposed to solve the serious coupling problem and improve start control performance. In the proposed decoupling control method, the main field current is estimated first and used in the closed‐loop excitation control for the ME to make the main field current meet the MM demand. With the desired field current, the MM is decoupled with the ME and controlled like a traditional synchronous motor to start the aircraft engine under maximum torque per ampere. The feasibility and effectiveness of the proposed decoupling control method is verified by experimental results.
Extended fast decoupled power flow for reconfiguration networks in distribution systems
Authors: Fonseca Alexandre G. , Tortelli Odilon L. , Lourenço Elizete M.
Published: October 2018

This study proposes a power flow methodology focused on the need for reconfiguration analysis in modern distribution networks. The proposal is based on the extended fast decoupled Newton–Raphson method, which uses the information of the network switching equipment status (open or closed). To deal with eventual islanding during a reconfiguration procedure, a numerical observability technique used in state estimation analysis has been adapted for topological processing when network segments are disconnected from voltage references. A complex per unit normalisation technique is employed so that the power flow calculation by the fast decoupled approach is viable, even for networks having high R/X ratio lines. Simulation results considering two distribution feeders, one of large size, with different topological conditions are presented. The performance of the proposed methodology qualifies it as a relevant computational tool to support network reconfiguration studies involving emergent distribution systems.
Multi‐scale classification network for road crack detection
Authors: Feng Hui , Xu Guo‐sheng , Guo Yanhui
Published: October 2018

Feature maps of different scales in convolutional neural networks (CNNs) can be regarded as image pyramids. In classification tasks, only the last layer of feature maps is used for making decision. However, in tasks such as road crack detection, the target objects are so small that some original information might lose during the downsampling process in CNN. The authors propose a structure that uses the information that is contained in different layers of feature maps, so all the information could contribute to the classification. This process is managed by adding the weighted values of pixels in corresponding regions of different layers in feature maps and using the sum of these values as the output. The authors apply this structure on a residual network and use it to learn the features of road cracks. Experiments have shown that with the authors’ structure, the network performs better than others at understanding and detecting road cracks.
Axial‐flux permanent‐magnet synchronous generator with coreless armature and non‐integral coil–pole ratio
Authors: Wu Danqi , Yang Junhua , Chan Tze Fun , Lai Chun Sing , Li Xuecong , Yan Baiping , Lai Loi Lei , Wang Dongxiao , Gao Xiaodan , Meng Ke
Published: October 2018

This article presents a study on an axial‐flux permanent‐magnet synchronous generator (AFPMSG) with a double‐sided rotor, coreless armature. The armature winding consists of non‐overlapping concentrated coils and has a non‐integral coil–pole ratio. It is shown that, with an appropriate choice of armature coil number to pole number, the fundamental winding factor of the AFPMSG can be made close to that of a full‐pitched integral slot winding. The field distribution and load performance are computed for a prototype machine based on a two‐dimensional, time‐stepping finite element method. A study of the armature reaction effect of the coreless armature winding and the origin of torque ripple is also carried out. The computed voltage and current waveforms, as well as the load characteristics, are verified by practical experiments.
Mining the underlying relation network based on the communication actions
Authors: Xiang Yingzhuo , Wei Qiang , You Ling
Published: October 2018

Information diffusion and virus propagation are fundamental processes, which achieve great attention in networks. While information spreads across the network, but the relations between the nodes, the underlying relation network, are usually unknown, and the authors only observe the time which transactions take place between nodes, called communication actions. Furthermore, the content of such transactions is unknown in many applications. They tackle these challenges by developing the NetMine algorithm to infer the relations between nodes and find out the underlying relation network, which is hidden from them. Given the times when nodes transmit a message to others (i.e. who sends a message to whom at some explicit time), they infer the optimal underlying relation network that best explains the observed communication actions. They demonstrate the effectiveness of their algorithm on synthetic and real networks, outperforming the art‐of‐date algorithms related to this problem.
Visual prediction of gas diffusion concentration based on regression analysis and BP neural network
Authors: Wang Jing , Fang Jiandong , Zhao Yvdong
Published: October 2018

In order to realise the prediction of the diffusion trend of chemical gases under toxic, flammable, and explosive conditions, this article used a multiple regression model and a back propagation (BP) neural network model, established two kinds of leakage gas diffusion models based on Fluent simulation data. First, the multivariate function relation between multiple influencing factors and diffusion concentration is established by using linear fitting method, i.e. multivariate regression model. Second, according to the large number and non‐linearity of Fluent simulation data of leakage gas, a three‐layer BP neural network prediction model for leakage gas, wind speed, X ‐axis diffusion distance, and Y ‐axis diffusion distance was established by using BP neural network algorithm. Under the same data conditions, the prediction error of BP neural network prediction model is smaller than that of multivariate reversion model, and the fitting degree is high, but the stability of multiple linear regression is better.
Design and analysis of an active‐controlled hydraulic low‐frequency vibration isolator
Authors: Guo Ning , Wang Fan , Wang Linxiang
Published: October 2018

This study proposes an active‐controlled hydraulic low‐frequency vibration isolator. The vibration isolator can achieve large equivalent mass and quasi‐zero dynamic stiffness by combining the fluid inerter with the hydraulic active compensation. Thus, good vibration isolation performance at ultra‐low frequency can be realised. The model for the dynamics of the device is set up. The principle of low‐frequency vibration isolation is explicated. The natural frequency and its influencing factors are analysed. Finally, preliminary experimental research works are carried out. The results indicate that low‐frequency vibration can be effectively isolated by the device proposed in this study.
Research on differential performance of four‐wheel independent steering of a hydraulic wheel‐driving off‐road vehicle
Authors: Wang Li , Liu Xinhui , Wang Xin , Fu Beibei , Xu Ran
Published: October 2018

Steering differential performance is an important factor affecting the driving performance of the vehicle. A hydraulic control method is proposed for the differential system of the hydraulic wheel‐driving off‐road vehicle, and the driving force equalisation technique is adopted to realise the adaptive steering differential under the different speed modes. Based on the analysis of the working principle of static pressure driving steering differential, the mathematical model of the steering differential system is derived by using kinematics and dynamics theory. The hydraulic driving system and multibody dynamics model are established by AMESim and LMS Virtual.Lab Motion, respectively, and joint simulation is carried out. The experimental scheme is designed for the typical working conditions in the simulation, and the rotation speed and the pressure differential of the motor in the steady state are analysed. The experimental results are consistent with the theoretical analysis and simulation results, which indicate that the system can achieve a better steering differential performance. This research provides a new idea for the study of the steering performance of the hydraulic wheel‐driving walking system, which is of great practical significance to improve the driving performance of off‐road vehicles under the complex terrain.
Mechanical simulation and installation position optimisation of a lifting cylinder of a scissors aerial work platform
Authors: He Shanghong , Ouyang Min , Gong Jianqiu , Liu Guoliang
Published: October 2018

The force of a lifting cylinder is the main factor of the alternating stress of scissors arms in a scissors aerial work platform, which seriously affects the fatigue life of structures. Aiming at this problem, the installation position parameters that affect the force of the lifting cylinder was simulated and optimised. First, the mechanical model of the lifting system was established based on the principle of virtual work, and the position parameters that affect the force of lifting cylinder were determined. Then, the advanced modeling environment for performing simulation of engineering systems (AMESim) simulation model was used to simulate the lifting process of the lifting system, and the reliability of the simulation model was verified by the pressure test of the hydraulic system. Finally, based on the simulation model, the design of experiment method was used to optimise the installation position of the lifting cylinder in the design and development environment of AMESim, and the optimisation effect was verified through the test on a real vehicle. The result shows that the peak load of the lifting cylinder is reduced by ∼12%, and the average of the steady‐state value decreases by ∼20% after the installation position is optimised.
Vibration characteristics of the two‐stage throttle valve induced by cavitation
Authors: Li Beibei , Li Ruirui , Yan Jingwei , Liu Xiumei , Wang Bingyang
Published: October 2018

The effect of cavitation on vibration characteristics of a two‐stage throttle valve is experimentally studied by changing inlet pressure, outlet pressure and opening. The shadow photograph of the flow field in the throttle is obtained by a high‐speed camera, and the signal of vibration induced by cavitation of the two‐stage throttle is obtained by an acceleration sensor. It can be concluded that the fixed cavitation and the travelling cavitation in the two‐stage throttle valve occur at the back of the throttle orifice. The effect of cavitation on vibration intensity and power spectral density is obvious. There are two frequency peaks in the spectrum, which are located in the vicinity of 7.5 and 12.5 kHz, respectively. These peaks correspond to travelling cavitation and fixed cavitation. The cavitation vibration intensity increases with the increase in the cavitation intensity, and the centre frequency of the signal peak near 7.5 kHZ is also moving towards the low frequency.
Transmission characteristics of magnetic resonance coupling‐based multi‐load wireless power transmission system
Authors: Li Changsheng , Cao Juan , Hu Defu , Zhang He
Published: October 2018

If the magnetic resonance coupling‐based wireless power transmission system has multiple receivers, cross‐coupling will occur between the transmitter and the receiver, resulting in the variation of transmission characteristics when compared with the case of a single receiver. To solve this problem, a mutual inductance coupling circuit model for double‐relay and multi‐load transmission system and a calculation model for mutual inductance between solenoid coils in the same plane have been built to study the transmission characteristics of the system through simulation and testing. The study results show that: the cross‐coupling effect between the transmitter and the receiver will cause resonance frequency shift, or even lead to the variation of resonance frequency splitting characteristic; when compared with a single‐load system, the multi‐load system may increase in total transmission power and efficiency; generally, with the introduction of additional receivers, the receiving power and efficiency of the original loads will decrease; along with the increase in circuit spacing and the decrease in cross‐coupling, the transmission characteristics will gradually regress to the state of a single‐load system. In this article, the calculation model for mutual inductance is correct and the maximum relative error in these calculating examples is 5.28%.
Design of a high water‐based fluid, high‐pressure, and large‐flow safety valve
Authors: Li Geqiang , Li Liaoyuan , Guo Bingjing , Li Yuesong
Published: October 2018

Aiming at solving the problem of low unloading sensitivity, bad dynamic performance and poor stability of high‐pressure and large‐flow relief valve in hydraulic support system, a new differential type of high‐pressure and large‐flow relief valve, functioned by high water‐based hydraulic medium, is designed. Through analysing the influence of spool form, elastic element, and working principle on valve performance, a structural scheme of large‐flow and high‐pressure safety valve is put forward. The three‐dimensional fluid–solid coupling model of differential safety valve is established; through ADINA software, three‐dimensional fluid–solid coupling simulation of relief valve's orifice from shutdown to full opening is carried out to analyse the distribution of internal pressure in the flow field of the safety valve and the pressure change of the structure field. The physical simulation model of safety valve is established by using AMESim software, and the dynamic performance of safety valve is simulated under the given signal of nominal flow and small flow. According to the design structure, the safety valve with the rated flow of 3000 L/min is manufactured and tested. The simulation and experimental results show that the safety valve has good dynamic performance and high sensitivity..
Dynamic and static sealing performance of elastic check valve spool
Authors: Cao Chao , Zhao Jiyun , Li Gulin , Jin Xin , Cao Zijian
Published: October 2018

The non‐metallic valve spool has the advantages of safety, stability, and biocompatibility. In order to expand the application of non‐metallic elastic valve spool in medical water jet, a check valve spool structure with double‐protrusion structure of polyurethane is designed to replace the metal valve spool and the spring thus achieves control of the fluid. Based on the non‐linear mechanical response of elastic materials, ANSYS Workbench was used to calculate the stress and deformation under the different friction coefficient and pre‐compression. The results show that the static sealing effect of the valve spool is best when the pre‐compression is 0.1 mm and the friction coefficient between the spool and the valve sleeve is 0.2. Then, based on bidirectional fluid–solid coupling analysis through Fluent, the flow field changes during the interaction between fluid and elastic material and the key bearing position of the valve spool are clarified. The results shows that size, processing quality, and material properties of the inner ring protrusion will determine the dynamic sealing performance of elastic valve spool.
Analysis on anti‐wear mechanism of bionic non‐smooth surface based on discrete phase model
Authors: Gao Dianrong , Liu Jingcheng , Xu Xuehan , Zhang Zongyi
Published: October 2018

In order to study the lubrication and anti‐wear mechanism of the pit‐type bionic non‐smooth surface used in the low‐speed and high‐torque seawater hydraulic motor valve plate pair, the discrete phase models of the four pits are simulated under different working conditions. In this study, the trajectories of different diameters particles in the hemispherical pits are analysed, which can reflect the movement of different sizes and masses wear debris in the pits. The discrete phase concentration distributions of the four‐kind pits, hemispherical pits, cylindrical pits, four‐prism pits and tri‐prism pits, are simulation under the same working conditions, which reflects the effect of pit geometry on the movement of wear debris. The discrete phase concentration distributions of four pits moving at different rotation speeds and different rotation radii are calculated, which indicates that the rotation speed of the motor and the distribution of pits on the valve plate will affect the ability of the pit to store wear debris.
Fault diagnosis approach of rolling bearing based on NA‐MEMD and FRCMAC
Authors: Liu Sheng , Sun Yue , Zhang Lanyong
Published: October 2018

This paper proposed a new method of fault diagnosis based on Noise Assisted Multivariate Empirical Mode Decomposition (NA‐MEMD) and Fuzzy Recurrent Cerebellar Model Articulation Controller (FRCMAC) Neural Networks. Aiming at the problem that during the use of the NA‐MEMD method, the white noise amplitude parameter needs to be selected by artificial experience, a method of using Genetic Algorithm (GA) to optimize its auxiliary white noise parameters is proposed, which facilitates the use of NA‐MEMD. We proposed a novel FRCMAC structure which improved Learning efficiency and dynamic response speed than traditional CMAC structure. First, the GA‐NA‐MEMD method is applied to process the vibration signals of rolling bearings, and the signals are decomposed into a group of Intrinsic Mode Functions (IMFs). Then use energy moments of IMFs as fault feature vectors to train FRCMAC neural network, a neural network structure suitable for rolling bearing fault diagnosis is obtained. Finally, the data from bearing data center of Case Western Reserve University is used to prove that the fault diagnosis method proposed in this paper is superior to other methods in diagnosis time and precision, which can meet the training requirements more quickly with limited training samples and fault diagnosis results more accurate.
Combined IR and XPS characterization of organic refractory residues obtained by ion irradiation of simple icy mixtures
Authors: Accolla M. , Pellegrino G. , Baratta G. A. , Condorelli G. G. , Fedoseev G. , Scirè C. , Palumbo M. E. , Strazzulla G.
Published: October 2018

Context. Multi-year laboratory experiments have demonstrated that frozen icy mixtures containing simple organic and inorganic molecules (such as H2O, N2, CH4, CO, CO2, C2H6, etc.), if exposed to a flux of energetic ions or UV photons, give rise to new more complex molecules at low temperatures (10–50 K). A fraction of the new synthesized molecules is volatile while the remaining fraction is refractory and therefore it is preserved after the warm-up of the substrate to room temperature. Moreover, a part of the refractory material is formed during the annealing to room temperature, when molecules and radicals into the processed ice become mobile and react to form non-volatile molecules. By means of similar mechanisms, complex organic materials may be formed on the icy surfaces of some objects in the outer solar system, such as trans-Neptunian objects, comets and some satellites of the giant planets: in fact the interaction with solar wind and solar flares ions, solar photons and galactic cosmic rays could produce more refractory materials, analogous to those produced in the laboratory. In some cases, the materials thus synthesized may contain functional groups considered relevant to the pre-biotic chemistry in the hypothesis that interplanetary dust particles, comets and meteoroids contributed to seed the early Earth with the building blocks of life.

Aims. The aim of this work is to investigate the chemical similarities and differences between some organic residues left over after ion bombardment (200 keV H+) of different ice mixtures followed by subsequent warm up under vacuum to room temperature.

Methods. Seven organic residues have been prepared in our laboratory following a procedure involving the proton irradiation of seven different icy mixtures and their warm-up to room temperature. All the organic samples were characterized by FTIR spectroscopy with measurements performed in situ, in the ultra-high vacuum condition preventing any sample degradation. Three of them were selected to be characterized by XPS spectroscopy as well.

Results. Among the organic residues presented in this paper, only those containing nitrogen and carbon exhibit the multi-component band centred at 2200 cm−1. This multi-component band presents interest from the astrobiological point of view due to its attribution to nitriles (–C≡N) and isonitriles (–N≡C). Our results demonstrate that this band is present in the IR spectra of organic nitrogen residues regardless the use of oxygen-bearing species in the icy mixture. This finding is of interest since the 2200 cm−1 band has been observed in some extraterrestrial samples (micro-meteorites) collected in the Antarctica.