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1 – 10 of over 300000

Abstract

Details

Functional Structure and Approximation in Econometrics
Type: Book
ISBN: 978-0-44450-861-4

Article
Publication date: 22 April 2022

Lijun Shang, Qingan Qiu, Cang Wu and Yongjun Du

The study aims to design the limited number of random working cycle as a warranty term and propose two types of warranties, which can help manufacturers to ensure the…

Abstract

Purpose

The study aims to design the limited number of random working cycle as a warranty term and propose two types of warranties, which can help manufacturers to ensure the product reliability during the warranty period. By extending the proposed warranty to the consumer's post-warranty maintenance model, besides the authors investigate two kinds of random maintenance policies to sustain the post-warranty reliability, i.e. random replacement first and random replacement last. By integrating depreciation expense depending on working time, the cost rate is constructed for each random maintenance policy and some special cases are provided by discussing parameters in cost rates. Finally, sensitivities on both the proposed warranty and random maintenance policies are analyzed in numerical experiments.

Design/methodology/approach

The working cycle of products can be monitored by advanced sensors and measuring technologies. By monitoring the working cycle, manufacturers can design warranty policies to ensure product reliability performance and consumers can model the post-warranty maintenance to sustain the post-warranty reliability. In this article, the authors design a limited number of random working cycles as a warranty term and propose two types of warranties, which can help manufacturers to ensure the product reliability performance during the warranty period. By extending a proposed warranty to the consumer's post-warranty maintenance model, the authors investigate two kinds of random replacement policies to sustain the post-warranty reliability, i.e. random replacement first and random replacement last. By integrating a depreciation expense depending on working time, the cost rate is constructed for each random replacement and some special cases are provided by discussing parameters in the cost rate. Finally, sensitivities to both the proposed warranties and random replacements are analyzed in numerical experiments.

Findings

It is shown that the manufacturer can control the warranty cost by limiting number of random working cycle. For the consumer, when the number of random working cycle is designed as a greater warranty limit, the cost rate can be reduced while the post-warranty period can't be lengthened.

Originality/value

The contribution of this article can be highlighted in two key aspects: (1) the authors investigate early warranties to ensure reliability performance of the product which executes successively projects at random working cycles; (2) by integrating random working cycles into the post-warranty period, the authors is the first to investigate random maintenance policy to sustain the post-warranty reliability from the consumer's perspective, which seldom appears in the existing literature.

Details

Journal of Quality in Maintenance Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1355-2511

Keywords

Open Access
Article
Publication date: 19 April 2022

Liwei Ju, Zhe Yin, Qingqing Zhou, Li Liu, Yushu Pan and Zhongfu Tan

This study aims to form a new concept of power-to-gas-based virtual power plant (GVPP) and propose a low-carbon economic scheduling optimization model for GVPP considering…

Abstract

Purpose

This study aims to form a new concept of power-to-gas-based virtual power plant (GVPP) and propose a low-carbon economic scheduling optimization model for GVPP considering carbon emission trading.

Design/methodology/approach

In view of the strong uncertainty of wind power and photovoltaic power generation in GVPP, the information gap decision theory (IGDT) is used to measure the uncertainty tolerance threshold under different expected target deviations of the decision-makers. To verify the feasibility and effectiveness of the proposed model, nine-node energy hub was selected as the simulation system.

Findings

GVPP can coordinate and optimize the output of electricity-to-gas and gas turbines according to the difference in gas and electricity prices in the electricity market and the natural gas market at different times. The IGDT method can be used to describe the impact of wind and solar uncertainty in GVPP. Carbon emission rights trading can increase the operating space of power to gas (P2G) and reduce the operating cost of GVPP.

Research limitations/implications

This study considers the electrical conversion and spatio-temporal calming characteristics of P2G, integrates it with VPP into GVPP and uses the IGDT method to describe the impact of wind and solar uncertainty and then proposes a GVPP near-zero carbon random scheduling optimization model based on IGDT.

Originality/value

This study designed a novel structure of the GVPP integrating P2G, gas storage device into the VPP and proposed a basic near-zero carbon scheduling optimization model for GVPP under the optimization goal of minimizing operating costs. At last, this study constructed a stochastic scheduling optimization model for GVPP.

Details

International Journal of Climate Change Strategies and Management, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1756-8692

Keywords

Article
Publication date: 26 April 2022

Canjun Chen, Lelin Lv, Zhuofu Wang and Ran Qiao

Reasonable risk sharing is the key to the smooth implementation of infrastructure public-private partnership (PPP) projects and the optimization of benefit distribution…

Abstract

Purpose

Reasonable risk sharing is the key to the smooth implementation of infrastructure public-private partnership (PPP) projects and the optimization of benefit distribution among the participants. This study aims to explore the risk redistribution ratio between the government and the private sector under different degree of fairness concern.

Design/methodology/approach

Renegotiation is a mechanism to provide flexibility and make up for incompleteness of PPP contracts. However, the threshold value of risk redistribution ratio and negotiation cost are not explicitly considered in previous studies. In addition, these studies do not consider the influence of the fairness concern psychology on the negotiation process. To address these gaps, based on risk-income equilibrium analysis, this paper established the bargaining optimization model of PPP projects renegotiation considering the fairness concerns of the negotiating parties. Furthermore, this study analyzed the influence of fairness concern degree on negotiation thresholds, negotiation results, and negotiation incomes under three scenarios.

Findings

The results showed that excessive focus on the fairness of incomes may exclude the risk redistribution ratio that is most beneficial to project incomes from the negotiation threshold. Moreover, the increase in the fairness concerns of negotiating parties can reduce the negotiation success period, but the net income may not necessarily be improved.

Originality/value

The main contribution of this paper is to propose a new risk renegotiation methodology based on the risk-income equilibrium analysis, which is helpful to develop risk management strategies in the construction field. The research results can provide government with reference about renegotiation in decision making and provide theoretical support for the practice of PPP renegotiation.

Details

Engineering, Construction and Architectural Management, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0969-9988

Keywords

Open Access
Article
Publication date: 4 April 2022

Mohammed H. Fahmy, Ahmed Ageeb Elokl and Ramy Abdel-Khalek

The aim of this paper is to investigate the relationship between the ring structure of the twisted partial skew generalized power series ring R…

Abstract

Purpose

The aim of this paper is to investigate the relationship between the ring structure of the twisted partial skew generalized power series ring RG,;Θ and the corresponding structure of its zero-divisor graph Γ̅RG,;Θ.

Design/methodology/approach

The authors first introduce the history and motivation of this paper. Secondly, the authors give a brief exposition of twisted partial skew generalized power series ring, in addition to presenting some properties of such structure, for instance, a-rigid ring, a-compatible ring and (G,a)-McCoy ring. Finally, the study’s main results are stated and proved.

Findings

The authors establish the relation between the diameter and girth of the zero-divisor graph of twisted partial skew generalized power series ring RG,;Θ and the zero-divisor graph of the ground ring R. The authors also provide counterexamples to demonstrate that some conditions of the results are not redundant. As well the authors indicate that some conditions of recent results can be omitted.

Originality/value

The results of the twisted partial skew generalized power series ring embrace a wide range of results of classical ring theoretic extensions, including Laurent (skew Laurent) polynomial ring, Laurent (skew Laurent) power series ring and group (skew group) ring and of course their partial skew versions.

Details

Arab Journal of Mathematical Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1319-5166

Keywords

Article
Publication date: 27 April 2022

Khursheed Muhammad, Tasawar Hayat and Bashir Ahmad

This study aims to explore the combined impacts of velocity and thermal slips on hybrid nanomaterial (GO+Ag+kerosene oil) bounded between two parallel infinite walls…

Abstract

Purpose

This study aims to explore the combined impacts of velocity and thermal slips on hybrid nanomaterial (GO+Ag+kerosene oil) bounded between two parallel infinite walls (plates). Both the walls are separated by a distance. The upper wall is subjected to squeezing with velocity, while the lower wall stretches with velocity. A uniform magnetic field acts normally to the flow. Moreover, heat transmission is analyzed in the presence of Joule heating. Heat transport characteristics are investigated by imposing the Cattaneo–Christov (C–C) heat flux model. The behavior of velocities, skin friction and temperature under sundry variables are examined graphically.

Design/methodology/approach

The obtained partial differential equations (PDEs) related to the considered problem are nondimensionalized by choosing appropriated variables. These nondimensional PDEs are then solved by the numerical technique, finite difference method (FDM). For implementation of this method, the obtained nondimensional PDEs are converted into finite difference equations (FDEs) using forward difference (FD) toolkits.

Findings

Velocity of the hybrid nanomaterial decreases with higher Hartman number and velocity slip parameter, while it increases with increase in Reynolds and squeezing numbers. Temperature of the hybrid nanomaterial increases for large Hartman number, Eckert number and squeezing parameter, while it is reduced by higher thermal slip parameter, thermal relaxation time parameter and nanoparticle volume fractions for graphene oxide (GO) and silver (Ag). Skin friction is controlled through higher Reynolds number, while it intensifies with nanoparticle volume fractions for GO and Ag.

Originality/value

Here, the authors have investigated 2D flow of hybrid nanomaterial bounded between two parallel walls. The lower and upper walls are subjected to stretching and squeezing, respectively. The authors guarantee that all outcomes and numerical technique (FDM) results are original, neither submitted nor published in any journal before.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

Keywords

Open Access
Article
Publication date: 9 March 2022

Mohd Aslam, Mohd Danish Siddiqi and Aliya Naaz Siddiqui

In 1979, P. Wintgen obtained a basic relationship between the extrinsic normal curvature the intrinsic Gauss curvature, and squared mean curvature of any surface in a…

Abstract

Purpose

In 1979, P. Wintgen obtained a basic relationship between the extrinsic normal curvature the intrinsic Gauss curvature, and squared mean curvature of any surface in a Euclidean 4-space with the equality holding if and only if the curvature ellipse is a circle. In 1999, P. J. De Smet, F. Dillen, L. Verstraelen and L. Vrancken gave a conjecture of Wintgen inequality, named as the DDVV-conjecture, for general Riemannian submanifolds in real space forms. Later on, this conjecture was proven to be true by Z. Lu and by Ge and Z. Tang independently. Since then, the study of Wintgen’s inequalities and Wintgen ideal submanifolds has attracted many researchers, and a lot of interesting results have been found during the last 15 years. The main purpose of this paper is to extend this conjecture of Wintgen inequality for bi-slant submanifold in conformal Sasakian space form endowed with a quarter symmetric metric connection.

Design/methodology/approach

The authors used standard technique for obtaining generalized Wintgen inequality for bi-slant submanifold in conformal Sasakian space form endowed with a quarter symmetric metric connection.

Findings

The authors establish the generalized Wintgen inequality for bi-slant submanifold in conformal Sasakian space form endowed with a quarter symmetric metric connection, and also find conditions under which the equality holds. Some particular cases are also stated.

Originality/value

The research may be a challenge for new developments focused on new relationships in terms of various invariants, for different types of submanifolds in that ambient space with several connections.

Details

Arab Journal of Mathematical Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1319-5166

Keywords

Article
Publication date: 24 February 2022

Khaled M.M. Koriem, Nevein N. Fadl, Salwa R. El-Zayat, Eman N. Hosny and Fatma A. Morsy

The purpose of this study was designed to investigate anise oil and geranium oil to amend body weight, serum bile acid and vitamin D, and liver histology in depressed rats.

Abstract

Purpose

The purpose of this study was designed to investigate anise oil and geranium oil to amend body weight, serum bile acid and vitamin D, and liver histology in depressed rats.

Design/methodology/approach

Eighty male albino rats were divided into normal and depressed rats. Normal rats (40 rats) were divided into four equal groups: control, venlafaxine drug, anise oil and geranium oil groups. Depressed rats (40 rats) were divided into four equal groups: depressed rats, depressed rats + venlafaxine drug, depressed rats + anise oil and depressed rats + geranium oil groups. Body weight, food consumption and water intake were detected. Animal behavior, cerebral cortex and hippocampus neurotransmitters, serum bile acid and vitamin D and liver histology were also investigated in this study.

Findings

Body weight (117 ± 7.6 g), food consumption (5.6 ± 1.4 g/day) and water intake (8.7 ± 1.2 ml/day) were significantly decreased (p < 0.001) in depression compared to body weight (153 ± 7.6 g), food consumption (12.7 ± 1.6 g/day) and water intake (15.3 ± 1.6 ml/day) in control. Animal behavioral tests, e.g. sucrose preference (48.8 ± 1.5) test, distance traveled (70.0 ± 16.3), center square entries (0.20 ± 0.10), center square duration (52.18 ± 11.9), tail suspension (54.70 ± 2.9 s) test and forced swimming (134.4 ± 5.5 s) test were significantly decreased (p < 0.001) in depression compared to sucrose preference (89.2 ± 1.7) test, distance traveled (226 ± 90.1), center square entries (1.4 ± 1.8), center square duration (3.6 ± 2.0), tail suspension (19.3 ± 2.1 s) test and forced swimming (83.7 ± 3.6 s) test in control. Cerebral cortex and hippocampus areas neurotransmitters such as serotonin (7.4 ± 1.7 and 1.2 ± 0.54 pg/g tissue), dopamine (6.3 ± 1.5 and 0.86 ± 0.07 pg/g tissue), norepinephrine (8.1 ± 1.7 and 1.4 ± 0.41 pg/g tissue) and gamma aminobutyric acid (GABA) (1.3 ± 0.41 and 0.08 ± 0.04 µmole/g tissue), serum bile acid (46.8 ± 3.5 µmole/L) and vitamin D (1.3 ± 0.37 ng/ml) were significantly decreased (p?0.001) in depression compared to cerebral cortex and hippocampus areas neurotransmitters such as serotonin (16.8 ± 2.1 and 4.0 ± 1.4 pg/g tissue), dopamine (15.7 ± 2.0 and 1.8 ± 0.49 pg/g tissue) norepinephrine (18.2 ± 2.3 and 3.8 ± 1.3 pg/g tissue) and GABA (2.7 ± 0.62 and 0.16 ± 0.06 µmole/g tissue), serum bile acid (90.5 ± 4.3 µmole/L) and vitamin D (2.7 ± 0.58 ng/ml) in control. Depression induced injury to hepatic tissues. Oral supplementation with anise oil and geranium oil ameliorated body weight, serum bile acid and vitamin D and liver histology in depressed rats.

Originality/value

Depression treatment persists for a long time, so the search for a new herbal treatment is of concern due to available sources, cheap and no side effects of herbal plants. Anise oil and geranium oil improved body weight, food consumption, water intake, animal behavioral tests, cerebral cortex and hippocampus areas neurotransmitters, serum bile acid and vitamin D and liver histology in depression.

Details

Nutrition & Food Science , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0034-6659

Keywords

Article
Publication date: 22 March 2022

Pham Duc Tai, Malcolm Ringland Anderson, Truong Ton Hien Duc, Tung Quang Thai and Xue-Ming Yuan

Information sharing is one of essential collaboration methods for building effective system-level disruption responses and communication for supply chain resilience…

Abstract

Purpose

Information sharing is one of essential collaboration methods for building effective system-level disruption responses and communication for supply chain resilience. However, supply chain members are often reluctant to share the members' business information for fear of losing competitiveness. To facilitate the cooperation among these members, the supply chain members' should be made aware of the value of information. As a result, the purpose of this paper is to quantify the benefit of information sharing and evaluate its magnitude under various factors.

Design/methodology/approach

In this paper, information sharing is measured in a two-stage supply chain containing a manufacturer and a retailer. A demand function is constructed as a linear combination of a first-order autoregressive [AR(1)] process, the retail and reference prices. The values of information sharing are quantified for four scenarios: (1) no information sharing, (2) full information sharing, (3) limited information sharing and (4) partial information sharing. Based on the four scenarios, the conditions for valuable information sharing are determined. In addition, the impact of several demand parameters on the usefulness of information sharing is analyzed.

Findings

When the demand function is a pure AR(1) process (i.e. there is no impact from the retail and reference prices), information sharing is always valuable regardless of the autoregressive coefficient. Under the influence of the retail price and consumer behavior via the reference price, information sharing is not always beneficial. The boundaries for useful information sharing are analytically constructed. In addition to full information sharing, this study also quantifies the value of information under a partial sharing scheme. The results indicate that the information is more valuable as long as the information is inducible.

Originality/value

This study highlights several specific conditions for a beneficial information sharing agreement in consideration of consumer behaviors. These conditions enable supply chain members to design a sustainable partnership.

Details

Industrial Management & Data Systems, vol. 122 no. 4
Type: Research Article
ISSN: 0263-5577

Keywords

Article
Publication date: 7 March 2022

Anukaran Khanna, Neelaksh Singh and Bijoy K. Mukherjee

Unmanned aerial vehicles (UAVs) have wide applications in surveillance and reconnaissance without risking human life. Due to unbalanced payload distribution or in-flight…

Abstract

Purpose

Unmanned aerial vehicles (UAVs) have wide applications in surveillance and reconnaissance without risking human life. Due to unbalanced payload distribution or in-flight deployment, UAVs may undergo lateral center of gravity (c.g.) variations resulting in an asymmetric dynamic having significant longitudinal and lateral/directional coupling and hence more pronounced nonlinearity. Therefore, automatic control of UAVs becomes extremely difficult when it is forced to perform maneuvers under such imbalance in lateral mass distribution. The purpose of this paper is to design adaptive nonlinear control so that the UAV can perform some useful lateral/directional maneuver under lateral c.g. uncertainty.

Design/methodology/approach

First the nominal lateral/directional dynamics of a fixed-wing UAV is framed into strict feedback form and then the block backstepping approach is used to design the controller to execute horizontal turn and aileron roll maneuvers under no lateral c.g. variation. Thereafter, an adaptive block backstepping controller is designed to adapt to uncertainty in lateral c.g. position considering an approximate model of the asymmetric dynamics. The proposed adaptive scheme is validated against the same two maneuvers as considered for the nominal case.

Findings

First it is shown that the lateral/directional dynamics of a UAV can be converted to a block strict feedback form for executing some lateral/directional maneuvers. However, it was observed that the maneuver performance suffers significant performance degradation under lateral c.g. variations. To mitigate this issue, a simple and computationally inexpensive adaptive block backstepping scheme is proposed and validated. The adaptation law is further proved to be able to asymptotically estimate the actual c.g. location of the UAV.

Practical implications

The proposed control scheme allows the UAV to automatically adapt to lateral c.g. variations so that the intended maneuvers are performed without any noticeable loss in maneuver performance.

Originality/value

There are very few works available in the literature that address nonlinear control designs for executing specific lateral/directional maneuvers and, moreover, they consider symmetric UAVs or aircraft only. This paper addresses the practical problem of autonomous maneuvering for UAVs with unbalanced lateral mass distribution leading to shift of c.g. out of its plane of symmetry.

Details

Aircraft Engineering and Aerospace Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1748-8842

Keywords

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