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Available. Open Access. Open Access
Article
Publication date: 26 October 2021

Michael Kaku Minlah, Xibao Zhang, Philipine Nelly Ganyoh and Ayesha Bibi

This study investigates the existence of the environmental Kuznets curve (EKC) for deforestation for Ghana over the 1962–2018 the time period.

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Abstract

Purpose

This study investigates the existence of the environmental Kuznets curve (EKC) for deforestation for Ghana over the 1962–2018 the time period.

Design/methodology/approach

The study employs a time-varying approach, the bootstrap rolling window Granger causality test to achieve its set objectives.

Findings

The results from our study reveals an inverted “N” shape EKC for deforestation, implying that deforestation will initially decrease with increases in economic growth up to a certain income threshold and increases with further increases in economic growth beyond this income threshold up to a higher income threshold and then decrease with further increases in economic beyond the higher income threshold.

Practical implications

The results from the study project show that over time economic growth can serve as a natural panacea to cure and mitigate the ills of deforestation that have plagued Ghana's forests over the years.

Social implications

The results further highlight the important role of strong institutions in fighting the deforestation menace.

Originality/value

The originality of this study lies in its methodology which allows for feedback from deforestation to the economy. This is in contrast to earlier studies on the EKC for deforestation which allowed causality only from deforestation to the economy.

Details

Forestry Economics Review, vol. 3 no. 1
Type: Research Article
ISSN: 2631-3030

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Article
Publication date: 9 July 2020

Xin Liu, Junhui Wu, Yiyun Man, Xibao Xu and Jifeng Guo

With the continuous development of aerospace technology, space exploration missions have been increasing year by year, and higher requirements have been placed on the upper level…

285

Abstract

Purpose

With the continuous development of aerospace technology, space exploration missions have been increasing year by year, and higher requirements have been placed on the upper level rocket. The purpose of this paper is to improve the ability to identify and detect potential targets for upper level rocket.

Design/methodology/approach

Aiming at the upper-level recognition of space satellites and core components, this paper proposes a deep learning-based spatial multi-target recognition method, which can simultaneously recognize space satellites and core components. First, the implementation framework of spatial multi-target recognition is given. Second, by comparing and analyzing convolutional neural networks, a convolutional neural network model based on YOLOv3 is designed. Finally, seven satellite scale models are constructed based on systems tool kit (STK) and Solidworks. Multi targets, such as nozzle, star sensor, solar,etc., are selected as the recognition objects.

Findings

By labeling, training and testing the image data set, the accuracy of the proposed method for spatial multi-target recognition is 90.17%, which is improved compared with the recognition accuracy and rate based on the YOLOv1 model, thereby effectively verifying the correctness of the proposed method.

Research limitations/implications

This paper only recognizes space multi-targets under ideal simulation conditions, but has not fully considered the space multi-target recognition under the more complex space lighting environment, nutation, precession, roll and other motion laws. In the later period, training and detection can be performed by simulating more realistic space lighting environment images or multi-target images taken by upper-level rocket to further verify the feasibility of multi-target recognition algorithms in complex space environments.

Practical implications

The research in this paper validates that the deep learning-based algorithm to recognize multiple targets in the space environment is feasible in terms of accuracy and rate.

Originality/value

The paper helps to set up an image data set containing six satellite models in STK and one digital satellite model that simulates spatial illumination changes and spins in Solidworks, and use the characteristics of spatial targets (such as rectangles, circles and lines) to provide prior values to the network convolutional layer.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 8
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 26 July 2021

Hongxing Zheng, Xin Liu, Junhui Wu, Yiyun Man, Xibao Xu and Jifeng Guo

The purpose of this paper is to improve the efficiency of on-orbit operations through the top-level task design based on DoDAF. Based on the existing upper stage rocket…

207

Abstract

Purpose

The purpose of this paper is to improve the efficiency of on-orbit operations through the top-level task design based on DoDAF. Based on the existing upper stage rocket technology, orbit transfer vehicles (OTVs) have developed rapidly in recent years. However, the lack of decision guidance based on overall task analysis requires integrating top-level analysis and bottom-level execution to achieve the smooth development of full-process tasks.

Design/methodology/approach

Using the Department of Defense Architecture Framework (DoDAF) as a reference, this paper performs the top-level mission analysis modeling of the on-orbit rendezvous and capture of the OTV. Moreover, the typical operational view products are obtained, and the cooperative relations among the mission requirements, the system requirements, and the functional requirements are also analyzed.

Findings

The results show that the attitude of the OTV changes violently during the maneuver and rendezvous phases. In addition, the view products can be optimized based on the results.

Originality/value

The proposed DoDAF-based on-orbit task integration analysis method achieves the effective fusion of high-level analysis and bottom-level execution of OTV on-orbit rendezvous and capture task through the top-level task modeling, operation view generation and task relationship analysis. According to the requirements and constraints of the on-orbit rendezvous and capture task, the control instructions of the vehicle are efficiently generated under the DoDAF framework.

Details

Aircraft Engineering and Aerospace Technology, vol. 93 no. 6
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 9 April 2019

Gökçe Mehmet AY and Osman Nuri ÇELİK

Plasma transferred arc (PTA) coating is a novel method for surface-coating applications. In this method, the substrate is melted using a plasma arc, and surfacing agents such as…

203

Abstract

Purpose

Plasma transferred arc (PTA) coating is a novel method for surface-coating applications. In this method, the substrate is melted using a plasma arc, and surfacing agents such as carbides are introduced to the melt pool. The purpose of this study is to investigate the effect of boron carbide (B4C) in nickel-based coating on AISI 4140 steel.

Design/methodology/approach

Samples were tested on a ball-on-disc wear device, and the microstructure, as well as wear properties, were investigated using SEM and XRD.

Findings

The effect of B4C addition was shown to be linear, with a p-value of 0.0248, indicating strong evidence. The reason for this increase was found to be the increase in third-body generation resulting from hard phases that form couples with the soft base material, nickel. It was concluded that using 6 per cent B4C was the optimal solution.

Originality/value

In the literature, the effect of neither low temperature on a nickel coating with B4C nor B4C as a single surfacing agent in a nickel base has been investigated.

Details

Industrial Lubrication and Tribology, vol. 71 no. 4
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 14 September 2015

Chuanjun Liao, Xibao Xu, Hongrong Fang, Hongrui Wang and Man Man

The purpose of this paper is to develop a leakage model of metallic static seals, which can be used to accurately predict the leakage rate and study the corresponding seal…

252

Abstract

Purpose

The purpose of this paper is to develop a leakage model of metallic static seals, which can be used to accurately predict the leakage rate and study the corresponding seal characteristics. The metallic static seal is effectively applied to severe rugged environments where conventional seals cannot meet the needs. More research efforts for deepening the understanding of its seal characteristics are important for its effective and safe applications, of which the study about its leak is one key component.

Design/methodology/approach

In the microscopic observations of the turning surface that is general in the processing of flange surfaces, it is found that the spiral morphology is dominant, which had been also obtained by other researches. There are two potential leakage paths for the flange surface of spiral morphology, one is the radial direction perpendicular to the spiral ridges and the other is the circumferential direction along the spiral groove. Based on the microgeometry characteristics of spiral morphology, the micromorphology of turning flange surface is simplified for the calculation of leakage rate, and the simplified methods of the radial and circumferential leakage paths are presented separately. The topography of flange surface studied in this paper is actually measured, and the Abbott bearing surface curve is adopted to represent the micro-profiles parameters. The radial and circumferential leakage models are further developed based on the assumption of laminar flow of the viscous compressible gas.

Findings

The experiments used to verify the leakage models were carried out, and the experimental values are well agreed with the calculated values. As the contact pressure increases, the change rules of both radial and circumferential leakage rates are obtained and the obvious transition from radial leak to circumferential leak can be found. Using the proposed leakage models, the effects of the key micro-profiles parameters on the leakage rates are studied, and some specific conclusions are given simultaneously, which are favorable for the theoretical study and practical application of the metallic static seal.

Practical implications

By the interpretations of the micromorphology characteristics of turning flange surface, the leakage mechanism of the metallic static seal is further made clear. The proposed leakage model reveals the relationships between the key micro-profiles parameters and some sealing performances about the leakage and can predict the leakage rates of the metallic static seal used in various working conditions.

Originality/value

For the metallic static seal, the simplification of the radial leakage path and the radial leakage model are put forward for the first time, so the total leakage model can be systematically reported based on the micromorphology characteristics of turning flange surface. The effects of the key micro-profiles parameters on the seal behaviors including of the leak rate, critical contact pressure and transition from radial leak to circumferential leak etc are also clarified firstly.

Details

Industrial Lubrication and Tribology, vol. 67 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Available. Open Access. Open Access
Article
Publication date: 13 December 2019

Shiyi Chen and Wang Li

With China’s economic growth slowing down and the growth rate of fiscal revenue decreasing, the pressure on local government debts is further increasing. Under this background, it…

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Abstract

Purpose

With China’s economic growth slowing down and the growth rate of fiscal revenue decreasing, the pressure on local government debts is further increasing. Under this background, it is of great significance to clarify the relation between local government debts and China’s economic growth in order to give full play to the positive role of local debts in stabling growth. The paper aims to discuss this issue.

Design/methodology/approach

Therefore, this paper explores the impact of Chinese local government debt on economic growth from theoretical and empirical aspects, respectively, and compares the regional differences between different debts and economic growth dynamics.

Findings

In the theoretical model part, this paper constructs a three-sector dynamic game model, under the two circumstances of whether local government is subject to debt constraints, and examines the relation between local government debt and economic growth and other variables through numerical simulation. Research shows that when the government is not constrained by debt, there is an inverted “U” relation between government debt and economic growth. When the government is constrained by debt, the economic growth rate gradually decreases as the government debt increases.

Originality/value

In the theoretical analysis part, this paper tries to estimate the amount of local debts under different calibers and examines the impact of different types of local government debts on China’s economic growth and their regional differences. The results show that excessive accumulation of government hidden debts in the eastern region is not conducive to economic growth, while explicit debts in the central and western regions significantly contribute to local economic growth. The results of empirical analysis are basically consistent with the predictions of the theoretical model.

Details

China Political Economy, vol. 2 no. 2
Type: Research Article
ISSN: 2516-1652

Keywords

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Article
Publication date: 28 July 2022

Xiaoyan Jiang, Sai Wang, Yong Liu, Bo Xia, Martin Skitmore, Madhav Nepal and Amir Naser Ghanbaripour

With the increasing complexity of public–private partnership (PPP) projects, the amount of data generated during the construction process is massive. This paper aims to develop a…

430

Abstract

Purpose

With the increasing complexity of public–private partnership (PPP) projects, the amount of data generated during the construction process is massive. This paper aims to develop a new information management method to cope with the risk problems involved in dealing with such data, based on domain ontologies of the construction industry, to help manage PPP risks, share and reuse risk knowledge.

Design/methodology/approach

Risk knowledge concepts are acquired and summarized through PPP failure cases and an extensive literature review to establish a domain framework for risk knowledge using ontology technology to help manage PPP risks.

Findings

The results indicate that the risk ontology is capable of capturing key concepts and relationships involved in managing PPP risks and can be used to facilitate knowledge reuse and storage beneficial to risk management.

Research limitations/implications

The classes in the risk knowledge ontology model constructed in this research do not yet cover all the information in PPP project risks and need to be further extended. Moreover, only the framework and basic methods needed are developed, while the construction of a working ontology model and the relationship between implicit and explicit knowledge is a complicated process that requires repeated modifications and evaluations before it can be implemented.

Practical implications

The ontology provides a basis for turning PPP risk information into risk knowledge to allow the effective sharing and communication of project risks between different project stakeholders. It can also have the potential to help reduce the dependence on subjectivity by mining, using and storing tacit knowledge in the risk management process.

Originality/value

The apparent suitability of the nine classes of PPP risk knowledge (project model, risk type, risk occurrence stage, risk source, risk consequence, risk likelihood, risk carrier, risk management measures and risk case) is identified, and the proposed construction method and steps for a complete domain ontology for PPP risk management are unique. A combination of criteria- and task-based evaluations is also developed for assessing the PPP risk ontology for the first time.

Details

Construction Innovation , vol. 23 no. 5
Type: Research Article
ISSN: 1471-4175

Keywords

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