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Article
Publication date: 22 March 2013

Zhiyun Zou, Yao Xiao and Jianzhi Gao

The purpose of this paper is to attempt to realize the optimization of cascading failure process of urban transit network based on Load‐Capacity model, for better evaluating and…

1250

Abstract

Purpose

The purpose of this paper is to attempt to realize the optimization of cascading failure process of urban transit network based on Load‐Capacity model, for better evaluating and improving the operation of transit network.

Design/methodology/approach

Robustness is an essential index of stability performance for urban transit systems. In this paper, firstly, the static robustness of transit networks is analyzed based on the complex networks theory. Aiming at random and intentional attack, a concrete algorithm process is proposed on the basis of Dijstra algorithm. Then, the dynamic robustness of the networks, namely cascading failure, is analyzed, and the algorithm process is presented based on the Load‐Capacity model. Finally, the space‐of‐stations is adopted to build the network topology of Foshan transit network, and then the simulation analyses of static and dynamic robustness are realized.

Findings

Results show that transit network is robust to random attack when considering static robustness, but somewhat vulnerable to intentional attack. For dynamic robustness analysis, a large‐scale cascade of transit network may be triggered when the tolerance parameter α is less than a value, so that the robustness of transit network can be improved through some reasonable measures.

Practice implications

The results of this study provide useful information for urban transit network robustness optimization.

Originality/value

An effective method for analyzing the static and dynamic robustness of transit network is provided in this paper.

Article
Publication date: 25 February 2014

Mingwei Sun, Zenghui Wang and Zengqiang Chen

– This paper aims to present a fast, economical and practical attitude control design approach for flight vehicles operating within wide envelopes.

Abstract

Purpose

This paper aims to present a fast, economical and practical attitude control design approach for flight vehicles operating within wide envelopes.

Design/methodology/approach

Based on a linear disturbance observer, an enhanced proportional-derivative (PD) control scheme is proposed. Utilizing the data from the onboard gyro, the observer can treat the entire response of the system, with the exception of the control term, as a disturbance, and use the estimation of the disturbance to cancel out this response and thereby to effectively simplify the control channel. Using the stability margin tester, the explicit graphical tuning rules are given in a consistent way for the longitudinal dynamics based on the induction method. Mathematical simulations are performed for a highly maneuverable flight vehicle to test the proposed method, which are compared with the traditional PD and H8 control algorithms.

Findings

The proposed strategy for attitude control can be reformulated as a static-dynamic control algorithm and the robust synthesis method can be employed to determine the control parameters according to a specific performance configuration. The remarkable control performance robustness can be achieved as shown in the comparative simulations.

Practical implications

There is a sole parameter, steady gain, needed to be scheduled and it can be estimated with a high accuracy.

Originality/value

This paper applies the linear active disturbance rejection control scheme to flight control scenario. The proposed method can reduce the design and implementation complexity of attitude control for flight vehicles operating within a wide envelope, which originates from diverse time-varying flight dynamics. The new method converts the attitude control problem to a sole parameter gain scheduling problem, and there is no complicated and time-consuming multi-dimension interpolation needed for the control parameters.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86 no. 2
Type: Research Article
ISSN: 0002-2667

Keywords

Book part
Publication date: 1 October 2014

Amr Sadek Hosny

A number of studies have examined the role of typical demand supply factors in explaining inflation. The contribution in this chapter is to investigate the possible role of…

Abstract

A number of studies have examined the role of typical demand supply factors in explaining inflation. The contribution in this chapter is to investigate the possible role of product market imperfections on inflation and inflation persistence, especially among emerging market economies. Using a backward-looking Phillips curve framework in a dynamic panel framework of 105 countries over the 2008–2011 period, our findings suggest that product market competition, as measured by the World Economic Forum’s measure of goods market imperfections do have a significant impact on inflation persistence. On average, higher competition and efficiency in product markets reduces the inflation persistence effect especially in the MENA region and countries at lower stages of development.

Details

Risk Management Post Financial Crisis: A Period of Monetary Easing
Type: Book
ISBN: 978-1-78441-027-8

Keywords

Article
Publication date: 3 June 2021

Nipan Kumar Das Das and Mrinal Buragohain

The power framework has become a vital part in the day-to-day life and exhibits a rapid development in this current era. Due to the fact of huge power utilization, the power…

Abstract

Purpose

The power framework has become a vital part in the day-to-day life and exhibits a rapid development in this current era. Due to the fact of huge power utilization, the power frameworks fall under several power transmission-related concerns. Precisely, frequency deviation has generated a huge impact during power transmission; this in turn highly reduces the power system stability as well as reliability too.

Design/methodology/approach

To boost the system’s efficacy, this study proposes a neoteric closed loop feedback controller in which a control algorithm named correlative-elemental-curvature algorithm is introduced with a constant threshold.

Findings

With the aim of mitigating frequency deviation, a stability analysis technique called Retrofit Lyapunov’s method is deployed in the controller. This would simultaneously reduce the load disturbances along with tie-line synchronization issues faced with the prior controllers. Optimization is carried out with the aid of duelist optimization algorithm, which tunes the controller parameters thereby mitigating the complexities while designing a loop feedback controller power framework.

Originality/value

The efficacy of the proposed work is assessed with the aid of metrics, such as integral absolute error, accuracy and settling time. Thus, the proposed work enhances the system reliability as well as the stability by mitigating the frequency deviation related issues and guarantees reliable power transmission.

Article
Publication date: 30 November 2023

Anas Iftikhar, Imran Ali and Mark Stevenson

This study aims to analyse whether the presence of supply chain complexity (SCC) influences firms to improve their supply chain (SC) resilience and SC robustness capability. This…

Abstract

Purpose

This study aims to analyse whether the presence of supply chain complexity (SCC) influences firms to improve their supply chain (SC) resilience and SC robustness capability. This study also examines an important paradox: whether investing in both exploitation and exploration practices is conflicting or complementary to enabling SC resilience and robustness in the presence of SCC.

Design/methodology/approach

The authors used a survey-based approach to collect 242 useful responses from SC professionals of Pakistani firms, an important emerging economy context. The data were analysed with covariance-based structural equation modelling to statistically validate the model.

Findings

The analysis reveals several key findings: the presence of SCC has a direct, positive influence on SC resilience and SC robustness; while exploitation practices only partially mediate the nexus between SCC and SC resilience, they fully mediate the relationship between SCC and SC robustness; while exploration practices partially mediate the nexus between SCC and SC resilience, they do not mediate the relationship between SCC and SC robustness and SCC has a significant influence on SC resilience and SC robustness sequentially through exploitation and exploration (i.e. one after the other).

Practical implications

These findings help to reconcile the exploitation versus exploration paradox in cultivating SC resilience and SC robustness in the presence of SCC. The findings assist SC managers in determining how to deploy their limited resources most effectively to enhance SC resilience and SC robustness while facing SCC.

Originality/value

The authors devise and empirically validate a unique framework that demonstrates how the presence of SCC works as a stimulus to build SC resilience and SC robustness.

Details

Supply Chain Management: An International Journal, vol. 29 no. 2
Type: Research Article
ISSN: 1359-8546

Keywords

Article
Publication date: 12 December 2022

Rosa Hendijani and Mahdis Norouzi

In recent years, the COVID-19 pandemic has become one of the most impactful disruptions which has imposed high levels of uncertainty on supply chains around the world. Supply…

Abstract

Purpose

In recent years, the COVID-19 pandemic has become one of the most impactful disruptions which has imposed high levels of uncertainty on supply chains around the world. Supply chain integration (SCI) is highly recommended as an underlying mechanism that can facilitate the development of resilience and robustness as two dynamic capabilities. They can in turn positively influence firm performance and success during the disruptive conditions of COVID-19 era. The study aims to examine whether SCI as an enabler of resilience and robustness can improve firm performance during COVID-19 pandemic.

Design/methodology/approach

A theoretical model is developed to elaborate the relationship between SCI dimensions, resilience and robustness and firm’s operational and financial performance during the COVID-19 pandemic. A survey method is then used to empirically examine the model using a sample of 94 companies in the food industry in the province of Tehran, Iran, during the COVID-19 pandemic. This study makes several contributions. It provides a novel theoretical model on the relationship between SCI, resilience and robustness and firm performance and tests this model in a less-studied yet critical context (i.e. Iranian food industry) and during a disruptive era (i.e. COVID-19 pandemic).

Findings

The results support the positive effect of three SCI dimensions of internal, product and process integration on operational and financial performance during corona virus pandemic. Furthermore, internal and process integration have positive effects on resilience. Internal, product and process integration have positive effects on robustness. In addition, resilience mediates the effects of internal and product integration on both operational and financial performance, whereas robustness mediates the effect of internal and product integration on financial performance.

Research limitations/implications

This study was conducted in the Province of Tehran. To test and generalize the results, it is recommended to conduct this study in other places and countries.

Originality/value

These results highlight the importance of SCI dimensions as vital enablers of resilience and robustness and their consequent impact on firm’s performance during the COVID-19 pandemic.

Details

Journal of Global Operations and Strategic Sourcing, vol. 16 no. 2
Type: Research Article
ISSN: 2398-5364

Keywords

Article
Publication date: 2 June 2023

Qamar Ul Islam, Haidi Ibrahim, Pan Kok Chin, Kevin Lim and Mohd Zaid Abdullah

Many popular simultaneous localization and mapping (SLAM) techniques have low accuracy, especially when localizing environments containing dynamically moving objects since their…

Abstract

Purpose

Many popular simultaneous localization and mapping (SLAM) techniques have low accuracy, especially when localizing environments containing dynamically moving objects since their presence can potentially cause inaccurate data associations. To address this issue, the proposed FADM-SLAM system aims to improve the accuracy of SLAM techniques in environments containing dynamically moving objects. It uses a pipeline of feature-based approaches accompanied by sparse optical flow and multi-view geometry as constraints to achieve this goal.

Design/methodology/approach

FADM-SLAM, which works with monocular, stereo and RGB-D sensors, combines an instance segmentation network incorporating an intelligent motion detection strategy (iM) with an optical flow technique to improve location accuracy. The proposed AS-SLAM system comprises four principal modules, which are the optical flow mask and iM, the ego motion estimation, dynamic point detection and the feature-based extraction framework.

Findings

Experiment results using the publicly available RGBD-Bonn data set indicate that FADM-SLAM outperforms established visual SLAM systems in highly dynamic conditions.

Originality/value

In summary, the first module generates the indication of dynamic objects by using the optical flow and iM with geometric-wise segmentation, which is then used by the second module to compute the starting point of a posture. The third module, meanwhile, first searches for the dynamic feature points in the environment, and second, eliminates them from further processing. An algorithm based on epipolar constraints is implemented to do this. In this way, only the static feature points are retained, which are then fed to the fourth module for extracting important features.

Details

Robotic Intelligence and Automation, vol. 43 no. 3
Type: Research Article
ISSN: 2754-6969

Keywords

Article
Publication date: 27 January 2023

Yawen Li, Guangming Song, Shuang Hao, Juzheng Mao and Aiguo Song

The prerequisite for most traditional visual simultaneous localization and mapping (V-SLAM) algorithms is that most objects in the environment should be static or in low-speed…

Abstract

Purpose

The prerequisite for most traditional visual simultaneous localization and mapping (V-SLAM) algorithms is that most objects in the environment should be static or in low-speed locomotion. These algorithms rely on geometric information of the environment and restrict the application scenarios with dynamic objects. Semantic segmentation can be used to extract deep features from images to identify dynamic objects in the real world. Therefore, V-SLAM fused with semantic information can reduce the influence from dynamic objects and achieve higher accuracy. This paper aims to present a new semantic stereo V-SLAM method toward outdoor dynamic environments for more accurate pose estimation.

Design/methodology/approach

First, the Deeplabv3+ semantic segmentation model is adopted to recognize semantic information about dynamic objects in the outdoor scenes. Second, an approach that combines prior knowledge to determine the dynamic hierarchy of moveable objects is proposed, which depends on the pixel movement between frames. Finally, a semantic stereo V-SLAM based on ORB-SLAM2 to calculate accurate trajectory in dynamic environments is presented, which selects corresponding feature points on static regions and eliminates useless feature points on dynamic regions.

Findings

The proposed method is successfully verified on the public data set KITTI and ZED2 self-collected data set in the real world. The proposed V-SLAM system can extract the semantic information and track feature points steadily in dynamic environments. Absolute pose error and relative pose error are used to evaluate the feasibility of the proposed method. Experimental results show significant improvements in root mean square error and standard deviation error on both the KITTI data set and an unmanned aerial vehicle. That indicates this method can be effectively applied to outdoor environments.

Originality/value

The main contribution of this study is that a new semantic stereo V-SLAM method is proposed with greater robustness and stability, which reduces the impact of moving objects in dynamic scenes.

Details

Industrial Robot: the international journal of robotics research and application, vol. 50 no. 3
Type: Research Article
ISSN: 0143-991X

Keywords

Article
Publication date: 11 July 2022

Emmanuel Sawyerr and Christian Harrison

The purpose of this explorative research is to analyse the resilience of the United Kingdom's (UK) healthcare supply chains from a customer’s perspective in the light of the…

1661

Abstract

Purpose

The purpose of this explorative research is to analyse the resilience of the United Kingdom's (UK) healthcare supply chains from a customer’s perspective in the light of the coronavirus pandemic.

Design/methodology/approach

Using the capabilities of preparedness, robustness, recovery and adaptability as the foundational percept for supply chain resilience, 22 healthcare professionals in 17 of the UK's National Health Scheme (NHS) Trusts were interviewed to explore their personal and organisational approaches adopted relative to the provision of eye protection, gloves, gowns, aprons, masks and respirators. The Dynamic Capabilities View is mapped to the resilience capabilities and used to analyse the data from a transformational supply chain research perspective.

Findings

The supply chains were largely unprepared, which was not particularly surprising even though the availability of gloves was significantly better compared to the other personal protective equipment (PPE). Techniques adopted to ensure robustness and recovery revealed the use of unsanctioned methods such as extended use of PPE beyond recommended use, redefinition of guidelines, protocols and procedures by infection control and the use of expired PPE – all of which compromised customer well-being.

Research limitations/implications

As the paper views resilience through the lens of customers, it does not provide the perspectives of the supply chain practitioners as to the reasons for the findings and the challenges within these supply chains.

Practical implications

The compromise of the well-being of healthcare workers due to the vulnerabilities of healthcare supply chains is highlighted to managers and prescriptions for post-disruption adaptability are made.

Originality/value

This paper introduces transformative research to supply chain resilience research by uniquely looking at resilience from the customers' well-being perspective.

Details

International Journal of Physical Distribution & Logistics Management, vol. 53 no. 3
Type: Research Article
ISSN: 0960-0035

Keywords

Article
Publication date: 18 September 2019

A.V. Thomas and Biswajit Mahanty

This study aims to examine the interrelationship between resilience, robustness and bullwhip effect using an inventory- and order-based production control system being subjected…

Abstract

Purpose

This study aims to examine the interrelationship between resilience, robustness and bullwhip effect using an inventory- and order-based production control system being subjected to operational disruption in the customer demand process.

Design/methodology/approach

Control engineering techniques and simulation are employed for the supply chain dynamics study.

Findings

The results show that resilience and robustness are two conflicting performance characteristics and therefore, a tradeoff can be established between them. It is also observed that improvement in resilience and reduction of bullwhip effect can be achieved simultaneously through a proper selection of control parameters.

Originality/value

The work establishes a relationship between the resilient behavior of a supply chain and bullwhip effect.

Details

Kybernetes, vol. 49 no. 3
Type: Research Article
ISSN: 0368-492X

Keywords

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