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Article
Publication date: 19 January 2022

Zhihong Jin, Xiaohan Wang, Jiaqing Sun and Qi Xu

Energy groups are cargo owners with large amounts of energy sources (such as coal) to transport. To achieve a satisfactory tradeoff between the reliability requirements of the sea…

1373

Abstract

Purpose

Energy groups are cargo owners with large amounts of energy sources (such as coal) to transport. To achieve a satisfactory tradeoff between the reliability requirements of the sea transportation process and the need to control the investment cost, they usually set up a self-owned fleet supplemented by a chartered fleet. This paper aims to investigate the best fleet structure and to evaluate the investment scheme under volatile circumstances in the shipping market.

Design/methodology/approach

The authors construct a mathematical model to determine the ratio of the self-owned fleet to the total fleet to minimize fleet operating costs. The volatility of both freight rates and oil prices is taken into consideration. The CPLEX solver is used to empirically analyze real data from an energy group in China, and the ship investment plan is evaluated considering the technical and economic feasibility.

Findings

If the ratio of the self-owned fleet to the total fleet is increased to the optimal of 90.40%, the total operating cost is reduced by 33.98%. Thus, the energy group should increase its capacity with a Panamax vessel of approximately 82,000 DWT. Purchasing a 5-year-old secondhand ship and building a new ship both have good investment return indicators.

Originality/value

For cargo owners engaging in transporting bulk cargo domestically in China, the suggested fleet ratio can provide a reference with a universal application scale, given the boundary economic conditions (including the volatility of freight rates and oil prices in the shipping market) in the paper.

Details

Maritime Business Review, vol. 7 no. 3
Type: Research Article
ISSN: 2397-3757

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Article
Publication date: 2 October 2019

Heping He, Yanni Liu and Zhimin Zhou

With the rapid development of social media in the past few years, some dark aspects of usage have appeared, e.g., Weibo addiction. Therefore, the purpose of this paper is to…

575

Abstract

Purpose

With the rapid development of social media in the past few years, some dark aspects of usage have appeared, e.g., Weibo addiction. Therefore, the purpose of this paper is to address the question of how Weibo keeps users hooked.

Design/methodology/approach

The study utilizes the netnography method to explore the symptoms of Weibo addiction and how it is formed.

Findings

First, some Weibo users have typical symptoms of addictive behavior, such as withdrawal, loss of control and general living problems; second, narcissism plays an important role in the process of Weibo addiction and has a stronger effect on content generation than content consumption; third, some users use Weibo as a means to alleviate anxiety, but they can then become more anxious owing to addiction; and fourth, the effect of comments has two sides – on the one hand, comments are one kind of feedback to posts, satisfying posters’ social needs, while on the other hand, a storytelling system consists of one post and its comments, upon which some Weibo users become more dependent.

Research limitations/implications

This research is only a preliminary, exploratory study. Therefore, care should be taken when interpreting these findings.

Practical implications

This study should help social media service providers and users to pay attention to the risk of social media addiction. Social media service providers should take social responsibility, design more user-oriented guidelines for marketing ethics and launch more responsible marketing activities. Users should enhance self-control and better balance social media use and offline real life.

Originality/value

Netnography has not been widely used as an addictive behavior research technique. This study is further bolstered because it has also noticed the difference of addiction mechanisms between addictive micro-bloggers and their followers.

Details

Journal of Contemporary Marketing Science, vol. 2 no. 2
Type: Research Article
ISSN: 2516-7480

Keywords

Available. Open Access. Open Access
Article
Publication date: 14 December 2018

Xiaohan Li, Wenshuo Wang, Zhang Zhang and Matthias Rötting

Feature selection is crucial for machine learning to recognize lane-change (LC) maneuver as there exist a large number of feature candidates. Blindly using feature could take up…

1270

Abstract

Purpose

Feature selection is crucial for machine learning to recognize lane-change (LC) maneuver as there exist a large number of feature candidates. Blindly using feature could take up large storage and excessive computation time, while insufficient feature selection would cause poor performance. Selecting high contributive features to classify LC and lane-keep behavior is effective for maneuver recognition. This paper aims to propose a feature selection method from a statistical view based on an analysis from naturalistic driving data.

Design/methodology/approach

In total, 1,375 LC cases are analyzed. To comprehensively select features, the authors extract the feature candidates from both time and frequency domains with various LC scenarios segmented by an occupancy schedule grid. Then the effect size (Cohen’s d) and p-value of every feature are computed to assess their contribution for each scenario.

Findings

It has been found that the common lateral features, e.g. yaw rate, lateral acceleration and time-to-lane crossing, are not strong features for recognition of LC maneuver as empirical knowledge. Finally, cross-validation tests are conducted to evaluate model performance using metrics of receiver operating characteristic. Experimental results show that the selected features can achieve better recognition performance than using all the features without purification.

Originality/value

In this paper, the authors investigate the contributions of each feature from the perspective of statistics based on big naturalistic driving data. The aim is to comprehensively figure out different types of features in LC maneuvers and select the most contributive features over various LC scenarios.

Details

Journal of Intelligent and Connected Vehicles, vol. 1 no. 3
Type: Research Article
ISSN: 2399-9802

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Article
Publication date: 17 October 2024

LingFeng Huang, Liming Zhu, Shuxiang Yi, Xiaohan Zhang, Xiaojing Wang and Xiangyu Li

This paper aims to propose novel flexible structure-supported tilting-pad aerostatic bearings and to improve operational stability and vibration reduction of aerostatic bearings.

29

Abstract

Purpose

This paper aims to propose novel flexible structure-supported tilting-pad aerostatic bearings and to improve operational stability and vibration reduction of aerostatic bearings.

Design/methodology/approach

The authors established an aerostatic bearing-rotor test rig and designed two aerostatic tilting-pad bearings with different flexible support structure and an ordinary aerostatic tilting-pad bearing and then examined their effects in dynamic performance to assess the vibration reduction performance of different flexible structures. Furthermore, the authors proposed three gas supply methods and conducted experiments to study the influence of gas supply methods in the performance of bearings.

Findings

The experimental results show that among the three structures, the double-layer flexible structure-supported tilting-pad bearing demonstrates outstanding vibration damping performance and it significantly enhances the operational stability of the bearing-rotor system. Furthermore, the experimental results indicate that the gas supply method has a significant impact on the performance of the aerostatic bearing. There is a certain pressure difference between the gas supply pressure for the loading pads and that for the nonloading pads, which is advantageous for increasing the operational stability and reducing system vibration.

Originality/value

The authors designed novel flexible aerostatic tilting-pad journal bearing structures, which can enhance the operational stability and reduce vibrations of the bearing. Additionally, this article proposes an air supply method advantageous for increasing the stability of the bearing and reducing system vibrations.

Details

Industrial Lubrication and Tribology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 5 February 2024

Dongsheng Wang, Xiaohan Sun, Yingchang Jiang, Xueting Chang and Xin Yonglei

Stainless-clad bimetallic steels (SCBS) are widely investigated in some extremely environmental applications areas, such as polar sailing area and tropical oil and gas platforms…

227

Abstract

Purpose

Stainless-clad bimetallic steels (SCBS) are widely investigated in some extremely environmental applications areas, such as polar sailing area and tropical oil and gas platforms areas, because of their excellent anticorrosion performance and relatively lower production costs. However, the properties of SCBS, including the mechanical strength, weldability and the anticorrosion behavior, have a direct relation with the manufacturing process and can affect their practical applications. This paper aims to review the application and the properties requirements of SCBS in marine environments to promote the application of this new material in more fields.

Design/methodology/approach

In this paper, the manufacturing process, welding and corrosion-resistant properties of SCBS were introduced systematically by reviewing the related literatures, and some results of the authors’ research group were also introduced briefly.

Findings

Different preparation methods, such as rolling composite, casting rolling composite, explosive composite, laser cladding and plasma arc cladding, as well as the process parameters, including the vacuum degree, rolling temperature, rolling reduction ratio, volume ratios of liquid to solid, explosive ratio and the heat treatment, influenced a lot on the properties of the SCBS through changing the interface microstructures. Otherwise, the variations in rolling temperature, pass, reduction and the grain size of clad steel also brought the dissimilarities of the mechanical properties, microhardness, bonding strength and toughness. Another two new processes, clad teeming method and interlayer explosive welding, deserve more attention because of their excellent microstructure control ability. The superior corrosion resistance of SCBS can alleviate the corrosion problem in the marine environment and prolong the service life of the equipment, but the phenomenon of galvanic corrosion should be noted as much as possible. The high dilution rate, welding process specifications and heat treatment can weaken the intergranular corrosion resistance in the weld area.

Originality/value

This paper summarizes the application of SCBS in marine environments and provides an overview and reference for the research of stainless-clad bimetallic steel.

Details

Anti-Corrosion Methods and Materials, vol. 71 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 27 August 2024

Linjie Dong, Renfei Zhang, Xiaohan Liu, Jie Li, Xingsong Wang and Tian Mengqian

Regular cable trench inspection is crucial, and robotics automation provides an efficient and safer alternative to manual labor. However, existing robots have limited capabilities…

116

Abstract

Purpose

Regular cable trench inspection is crucial, and robotics automation provides an efficient and safer alternative to manual labor. However, existing robots have limited capabilities in traversing obstacles and lack a mechanical arm for detecting cables and equipment. This study aims to develop an intelligent robot for cable trench inspection, enhancing obstacle-crossing abilities and incorporating a mechanical arm for inspection tasks.

Design/methodology/approach

This study presents an intelligent robot for cable trench inspection, featuring a six-degree-of-freedom mechanical arm mounted on a six-track chassis with four flippers. The robot's climbing and obstacle-crossing stability, as well as the motion range of the mechanical arm, are analyzed. The positioning, navigation and remote monitoring systems are developed. Experiments, including climbing and obstacle-crossing performance tests, along with navigation and positioning system tests, are conducted. Finally, the robot's practicability is verified through field testing.

Findings

Equipped with flipper tracks, the cable trench inspection robot can traverse obstacles up to 30 cm high and maintain stable locomotion on 30° slopes. Its navigation system enables autonomous operation, while the mechanical arm performs cable current detection tasks. The remote monitoring system provides comprehensive control of the robot and environmental parameter monitoring in cable trenches.

Originality/value

The front and rear flipper tracks enhance the robot's ability to traverse obstacles in cable trenches. The mechanical arm addresses cable current and equipment contact detection issues. The navigation and remote monitoring systems improve the robot's autonomous operation and environmental monitoring capabilities. Implementing this robot can advance the automation and intelligence of cable trench inspections.

Details

Industrial Robot: the international journal of robotics research and application, vol. 52 no. 1
Type: Research Article
ISSN: 0143-991X

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Article
Publication date: 28 February 2023

Mingxiao Dai, Xu Peng, Xiao Liang, Xinyu Zhu, Xiaohan Liu, Xijun Liu, Pengcheng Han and Chao Wu

The purpose of this paper is to propose a DC-port voltage balance strategy realizing it by logic combination modulation (LCM). This voltage balance strategy is brief and high…

79

Abstract

Purpose

The purpose of this paper is to propose a DC-port voltage balance strategy realizing it by logic combination modulation (LCM). This voltage balance strategy is brief and high efficient, which can be used in many power electronic devices adopting the cascaded H-bridge rectifier (CHBR) such as power electronic transformer (PET).

Design/methodology/approach

The CHBR is typically as a core component in the power electronic devices to implement the voltage or current conversion. The modulation method presented here is aiming to solve the voltage imbalance problem occurred in the CHBR with more stable work station and higher reliability in ordinary operating conditions. In particular, by changing the switch states smoothly and quickly, the DC-port voltage can be controlled as the ideal value even one of the modules in CHBR is facing the load-removed problem.

Findings

By using the voltage balance strategy of LCM, the problem of voltage imbalance occurring in three-phase cascaded rectifiers has been solved properly. With the lower modulation depth, the efficiency of the strategy is shown to be better and stronger. The strategy can work reliably and quickly no matter facing the problem as load-removed change or the ordinary operating conditions.

Research limitations/implications

The limitation of the proposed DC-port voltage balance strategy is calculated and proved, in a three-module CHBR, the LCM could balance the DC-port voltage while one module facing the load-removed situation under 0.83 modulation depth.

Originality/value

This paper provides a useful and particular voltage balance strategy which can be used in the topology of three-phase cascaded rectifier. The value of the strategy is that a brief and reliable voltage balance method in the power electronic devices can be achieved. What is more, facing the problem, such as load-removed, in outport, the strategy can response quickly with no switch jump and switch frequency rising.

Details

Microelectronics International, vol. 40 no. 3
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 12 February 2024

Boyi Li, Miao Tian, Xiaohan Liu, Jun Li, Yun Su and Jiaming Ni

The purpose of this study is to predict the thermal protective performance (TPP) of flame-retardant fabric more economically using machine learning and analyze the factors…

132

Abstract

Purpose

The purpose of this study is to predict the thermal protective performance (TPP) of flame-retardant fabric more economically using machine learning and analyze the factors affecting the TPP using model visualization.

Design/methodology/approach

A total of 13 machine learning models were trained by collecting 414 datasets of typical flame-retardant fabric from current literature. The optimal performance model was used for feature importance ranking and correlation variable analysis through model visualization.

Findings

Five models with better performance were screened, all of which showed R2 greater than 0.96 and root mean squared error less than 3.0. Heat map results revealed that the TPP of fabrics differed significantly under different types of thermal exposure. The effect of fabric weight was more apparent in the flame or low thermal radiation environment. The increase in fabric weight, fabric thickness, air gap width and relative humidity of the air gap improved the TPP of the fabric.

Practical implications

The findings suggested that the visual analysis method of machine learning can intuitively understand the change trend and range of second-degree burn time under the influence of multiple variables. The established models can be used to predict the TPP of fabrics, providing a reference for researchers to carry out relevant research.

Originality/value

The findings of this study contribute directional insights for optimizing the structure of thermal protective clothing, and introduce innovative perspectives and methodologies for advancing heat transfer modeling in thermal protective clothing.

Details

International Journal of Clothing Science and Technology, vol. 36 no. 2
Type: Research Article
ISSN: 0955-6222

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Article
Publication date: 15 September 2023

Xiaohan Xu, Xudong Huang, Ke Zhang and Ming Zhou

In general, the existing compressor design methods require abundant knowledge and inspiration. The purpose of this study is to identify an intellectual design optimization method…

88

Abstract

Purpose

In general, the existing compressor design methods require abundant knowledge and inspiration. The purpose of this study is to identify an intellectual design optimization method that enables a machine to learn how to design it.

Design/methodology/approach

The airfoil design process was solved using the reinforcement learning (RL) method. An intellectual method based on a modified deep deterministic policy gradient (DDPG) algorithm was implemented. The new method was applied to agents to learn the design policy under dynamic constraints. The agents explored the design space with the help of a surrogate model and airfoil parameterization.

Findings

The agents successfully learned to design the airfoils. The loss coefficients of a controlled diffusion airfoil improved by 1.25% and 3.23% in the two- and four-dimensional design spaces, respectively. The agents successfully learned to design under various constraints. Additionally, the modified DDPG method was compared with a genetic algorithm optimizer, verifying that the former was one to two orders of magnitude faster in policy searching. The NACA65 airfoil was redesigned to verify the generalization.

Originality/value

It is feasible to consider the compressor design as an RL problem. Trained agents can determine and record the design policy and adapt it to different initiations and dynamic constraints. More intelligence is demonstrated than when traditional optimization methods are used. This methodology represents a new, small step toward the intelligent design of compressors.

Details

Engineering Computations, vol. 40 no. 9/10
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 8 November 2023

Yang Zhou, Zhong Li, Yuhe Huang, Xiaohan Chen, Xinggang Li, Xiaogang Hu and Qiang Zhu

Laser powder bed fusion (LPBF) in-situ alloying is a recently developed technology that provides a facile approach to optimizing the microstructural and compositional…

164

Abstract

Purpose

Laser powder bed fusion (LPBF) in-situ alloying is a recently developed technology that provides a facile approach to optimizing the microstructural and compositional characteristics of the components for high performance goals. However, the complex mass and heat transfer behavior of the molten pool results in an inhomogeneous composition distribution within the samples fabricated by LPBF in-situ alloying. The study aims to investigate the heat and mass transfer behavior of an in-situ alloyed molten pool by developing a three-dimensional transient thermal-flow model that couples the metallurgical behavior of the alloy, thereby revealing the formation mechanism of composition inhomogeneity.

Design/methodology/approach

A multispecies multiphase computational fluid dynamic model was developed with thermodynamic factors derived from the phase diagram of the selected alloy system. The characteristics of the Al/Cu powder bed in-situ alloying process were investigated as a benchmark. The metallurgical behaviors including powder melting, thermal-flow, element transfer and solidification were investigated.

Findings

The Peclet number indicates that the mass transfer in the molten pool is dominated by convection. The large variation in material properties and temperature results in the presence of partially melted Cu-powder and pre-solidified particles in the molten pool, which further hinder the convection mixing. The study of simulation and experiment indicates that optimizing the laser energy input is beneficial for element homogenization. The effective time and driving force of the convection stirring can be improved by increasing the volume energy density.

Originality/value

This study provides an in-depth understanding of the formation mechanism of composition inhomogeneity in alloy fabricated by LPBF in-situ alloying.

Details

Rapid Prototyping Journal, vol. 30 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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