Search results

1 – 10 of 54
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 2 October 2017

Reza Ebrahimi, Mostafa Ghayour and Heshmatallah Mohammad Khanlo

This paper aims to present bifurcation analysis of a magnetically supported coaxial rotor model in auxiliary bearings, which includes gyroscopic moments of disks and geometric…

108

Abstract

Purpose

This paper aims to present bifurcation analysis of a magnetically supported coaxial rotor model in auxiliary bearings, which includes gyroscopic moments of disks and geometric coupling of the magnetic actuators.

Design/methodology/approach

Ten nonlinear equations of motion were solved using the Runge–Kutta method. The vibration responses were analyzed using dynamic trajectories, power spectra, Poincaré maps, bifurcation diagrams and the maximum Lyapunov exponent. The analysis was carried out for different system parameters, namely, the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position.

Findings

It was shown that dynamics of the system could be significantly affected by varying these parameters, so that the system responses displayed a rich variety of nonlinear dynamical phenomena, including quasi-periodicity, chaos and jump. Next, some threshold values were provided with regard to the design of appropriate parameters for this system. Therefore, the proposed work can provide an effective means of gaining insights into the nonlinear dynamics of coaxial rotor–active magnetic bearing systems with auxiliary bearings in the future.

Originality/value

This paper considered the influences of the inner shaft stiffness, inter-rotor bearing stiffness, auxiliary bearing stiffness and disk position on the bifurcation behavior of a magnetically supported coaxial rotor system in auxiliary bearings.

Details

Engineering Computations, vol. 34 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Access Restricted. View access options
Article
Publication date: 14 October 2019

Alireza Fallahi, Fatemeh Fallahi, Hassan Sarhadi, S.F. Ghaderi and Reza Ebrahimi

This study evaluates the efficiency and productivity change of 39 electricity distribution companies in Iran over the period 2005-2014. For purposes of electricity management and…

317

Abstract

Purpose

This study evaluates the efficiency and productivity change of 39 electricity distribution companies in Iran over the period 2005-2014. For purposes of electricity management and utilization of scarce resources, Iran’s 33 provinces have been classified into five regions by the Ministry of the Interior. Analyzing the efficiency of distribution companies across these regions yields significant understanding of these resources and helps policymakers to generate more informed decisions.

Design/methodology/approach

The proposed method of this study develops nonparametric data envelopment analysis (DEA) with the consideration of geographic classification, size and type of company. At the first stage, a DEA model is used to estimate the relative technical efficiency and productivity change of these companies. At the second stage, distributions of efficiency improvements are examined based on geographic classification, size and type of the company type. A stability test is also conducted to verify the proposed model’s robustness.

Findings

The results demonstrate that the average technical efficiency of the companies increased during the years 2006-2009, but decreased during 2010-2014. The productivity measurement reveals that low efficiency change was the largest contributor to the small increase in productivity change rather than technology change. In addition, testing the hypothesis that the large and small companies have statistically the same efficiency scores revealed no statistical difference among them. Moreover, another test did not detect a difference among companies at the urban and provincial levels.

Practical implications

By applying this approach, policymakers and practitioners in the power industry at the country and corporate level can effectively compare the efficiency and productivity changes among electricity distribution companies, and therefore generate more informed decisions.

Originality/value

The paper’s novel concept applies DEA to Iran’s electricity distribution companies and analyzes them by examining geographic classification, size and the type of the companies. In addition, a stability test is conducted and productivity changes are estimated.

Details

International Journal of Energy Sector Management, vol. 15 no. 4
Type: Research Article
ISSN: 1750-6220

Keywords

Access Restricted. View access options
Article
Publication date: 18 May 2010

Miralam Mahdi, Mehrzad Shams and Reza Ebrahimi

The purpose of this paper is to study numerically the effects of heat transfer on the strength of shock waves emitted upon spherical bubble collapse.

330

Abstract

Purpose

The purpose of this paper is to study numerically the effects of heat transfer on the strength of shock waves emitted upon spherical bubble collapse.

Design/methodology/approach

The motion of bubble under ultrasound is predicted by solutions of the Navier‐Stokes equations for the gas inside a spherical bubble. The Gilmore model and the method of characteristics are used to model the shock wave emitted at the end of the bubble collapse.

Findings

The theory permits one to predict correctly the bubble radius‐time curve and the characteristics of shock wave in sulphuric acid solution. These simulations indicated that the heat transfer inside the bubble and the liquid layer plays a major role in the bubble behaviour and the strength of the shock waves. Also, the developed numerical scheme is checked for different gas bubble like air, Argon and Xenon. It is observed that the gas thermal conductivity plays an important role in the shock wave strength. A good agreement is observed by comparison of the results with the experimental data.

Originality/value

The effect of heat transfer on the emitted shock wave strength has not been studied previously. In this paper, a numerical scheme is developed to consider heat transfer on the shock. Also, this simulation is checked for different gas conductivities.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 20 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Available. Open Access. Open Access
Article
Publication date: 5 April 2018

Reza Ghazavi and Haidar Ebrahimi

Groundwater is an important source of water supply in arid and semi-arid areas. The purpose of this study is to predict the impact of climate change on groundwater recharge in an…

4711

Abstract

Purpose

Groundwater is an important source of water supply in arid and semi-arid areas. The purpose of this study is to predict the impact of climate change on groundwater recharge in an arid environment in Ilam Province, west of Iran.

Design/methodology/approach

A three-dimensional transient groundwater flow model (modular finite difference groundwater FLOW model: MODFLOW) was used to simulate the impacts of three climate scenarios (i.e. an average of a long-term rainfall, predicted rainfall in 2015-2030 and three years moving average rainfall) on groundwater recharge and groundwater levels. Various climate scenarios in Long Ashton Research Station Weather Generator were applied to predict weather data.

Findings

HadCM3 climatic model and A2 emission scenario were selected as the best methods for weather data generation. Based on the results of these models, annual precipitation will decrease by 3 per cent during 2015-2030. For three emission scenarios, i.e. an average of a long-term rainfall, predicted rainfall in 2015-2030 and three years moving average rainfall, precipitation in 2030 is estimated to be 265, 257 and 247 mm, respectively. For the studied aquifer, predicted recharge will decrease compared to recharge calculated based on the average of long-term rainfall.

Originality/value

The decline of groundwater level in the study area was 11.45 m during the past 24 years or 0.48 m/year. Annual groundwater depletion should increase to 0.75 m in the coming 16 years via climate change. Climate change adaptation policies in the basin should include changing the crop type, as well as water productivity and irrigation efficiency enhancement at the farm and regional scales.

Details

International Journal of Climate Change Strategies and Management, vol. 11 no. 1
Type: Research Article
ISSN: 1756-8692

Keywords

Access Restricted. View access options
Article
Publication date: 25 September 2019

Ahmad Naderi, Leila Nasrolahi Vosta, Abolghasem Ebrahimi and Mohammad Reza Jalilvand

The exploration of performance determinants in social enterprises has gained increasing relevance among researchers and practitioners, particularly in rural tourism. The purpose…

1836

Abstract

Purpose

The exploration of performance determinants in social enterprises has gained increasing relevance among researchers and practitioners, particularly in rural tourism. The purpose of this paper is to analyze the contributions of transformational leadership and social entrepreneurship to the performance of social enterprises in the context of rural tourism. Further, the mediating roles of social capital, creativity and social value were investigated.

Design/methodology/approach

Data were gathered through a survey of 168 employees of social enterprises operating in the rural tourism setting. Eight surveyors were sent out to conduct the survey. Data were analyzed by structural equation modeling (SEM) using AMOS 18.0.

Findings

The results of the SEM suggested that transformational leadership is positively associated with social value, social capital and performance of social enterprise. In addition, social entrepreneurship had a significant influence on social value, social capital and performance of social enterprise. Creativity and social value predicts the performance of social enterprise. Further, social capital was found to have a positive relationship with creativity. Finally, the mediating roles of social capital, creativity and social value were also confirmed. The findings thus highlight the power of the social value creation and social capital in the social enterprises operating in the rural destinations.

Social implications

The findings assert that social entrepreneurship and transformational leadership are key sources of social value creation, social capital and creativity in rural tourism context indicating the need for additional efforts on this kind of entrepreneurial activity. The findings can motivate policymakers to promote social entrepreneurship in rural tourism destinations as a means of stimulating bottom-up social capital and social value creation.

Originality/value

This study is among the first to examine the hypothesized relationships focusing on tourism social enterprises.

Details

International Journal of Sociology and Social Policy, vol. 39 no. 9/10
Type: Research Article
ISSN: 0144-333X

Keywords

Access Restricted. View access options
Article
Publication date: 1 March 2003

Mahommad Rafiqul Islam

This article examines the application of "resource dependency theory" to transnational corporations (TNCs) operating in host countries like Bangladesh to explain the relationship…

256

Abstract

This article examines the application of "resource dependency theory" to transnational corporations (TNCs) operating in host countries like Bangladesh to explain the relationship between the TNCs and Bangladesh. Data indicate that while the TNCs' participation in a third world host country is encouraged primarily for promoting its economic development, TNCs are mainly attracted by market size, purchasing capacities (determined mainly by GNP) of the population, and stable political condition of the country. Although examination of the application of resource dependency theory provides some insights into understanding the complicated relationship between TNCs and Bangladesh, several other factors, not explained by resource dependency theory, help explain the behavior of TNCs in a host country

Details

International Journal of Organization Theory & Behavior, vol. 6 no. 3
Type: Research Article
ISSN: 1093-4537

Access Restricted. View access options
Article
Publication date: 30 December 2024

Mohammad Gharipour, Ehsan Masoud, Jamal Esmaeilzadeh Vafaei and Fateme Jahani Sadatmahalle

The advancement of medical care during the late 19th century and the rising importance of public health led to the creation of a healthcare infrastructure in Iran in the early…

17

Abstract

Purpose

The advancement of medical care during the late 19th century and the rising importance of public health led to the creation of a healthcare infrastructure in Iran in the early decades of the 20th century. The study focuses on the formation of this infrastructure through the study of historical materials as well as the study of case studies built in the Gilan region in the north of Iran.

Design/methodology/approach

This paper begins with a review of medical, sociological and historical resources, then turns to field studies and interviews as methods to focus on the medical transformations in the Gilan region.

Findings

This study offers four key findings: First of all, most studies tend to focus more on traditional medicine in Iran than on the initiation and spread of modern medicine. Secondly, foreign physicians and missionaries played an influential role in shaping the culture of Iranian hospital care. Thirdly, the interactions with and influences coming from Iran’s northern neighbors in Gilan transformed the province into an educated, freedom-seeking society. And finally, in its early stages, hospital construction in Iran followed local architectural traditions.

Originality/value

In the case of Gilan, the core structures of urban hospitals were similar in their pavilion typology to those that had been common in Gilan for centuries.

Details

Archnet-IJAR: International Journal of Architectural Research, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2631-6862

Keywords

Access Restricted. View access options
Article
Publication date: 25 February 2014

Zahra Fallah Ebrahimi, Chin Wei Chong and Reza Hosseini Rad

The aim of this paper is to evaluate the impact of total quality management (TQM) practices on role stressors in Iranian manufacturing SMEs in order to determine the relationship…

2277

Abstract

Purpose

The aim of this paper is to evaluate the impact of total quality management (TQM) practices on role stressors in Iranian manufacturing SMEs in order to determine the relationship between the multidimensionality of TQM practices and role ambiguity, role conflict and role overload.

Design/methodology/approach

Questionnaires are administrated to 410 employees of 100 different manufacturing SMEs in Iran.

Findings

The results support important negative association among some of TQM practices (such as employee involvement, information analysis, process management, supplier management, strategic planning and customer focus) and role conflict, role ambiguity, role overload. By utilizing multiple regression analysis, information analysis, supplier management, employee involvement, process management, customer focus, strategic planning are found to have significant and negative relationship with role stressors. Leadership and human resource focus are found to have significant and positive relationship with role stressors.

Practical implications

This model is perfect for practical usage by SME managers to estimate the perceptions of role stressors of employees in TQM oriented firms. The findings recommend that manufacturing should look into ways of improving the major roles of TQM practices in order to decrease the negative role stressors of employees.

Originality/value

TQM practices emerge to be related to role stressors (role ambiguity, role conflict and role overload), attending to an obvious noticeable gap in the previous studies of TQM and the psychological welfare of employees.

Details

International Journal of Quality & Reliability Management, vol. 31 no. 2
Type: Research Article
ISSN: 0265-671X

Keywords

Access Restricted. View access options
Article
Publication date: 8 September 2020

Artur Strzelecki and Mariia Rizun

This paper aims to consider the question of changes brought to consumers’ trust and security issues by the implementation of the General Data Protection Regulation (GDPR) in…

1603

Abstract

Purpose

This paper aims to consider the question of changes brought to consumers’ trust and security issues by the implementation of the General Data Protection Regulation (GDPR) in electronic commerce.

Design/methodology/approach

Online shopping policies in Poland and Ukraine are compared from the perspective of four factors as follows: application of terms of service and privacy policy, usage of online payment systems, presence in price comparison engines and grade of secure sockets layer security certificates. Comparison is conducted within the framework of three research questions (complemented by eight hypotheses) set to reveal whether: policies of personal data protection and server security for online stores in both countries are the same; all online stores in both countries obey the existing e-commerce rules; e-commerce policies in the two countries differ significantly. The sample for analysis contains 40 Polish and 40 Ukrainian online stores, representing four industries, namely, electronics, entertainment, fashion and goods for children.

Findings

The research allowed to reveal major differences in the privacy policy of the two countries, caused, mainly, by the absence of GDPR in Ukraine. It also disclosed much stronger cooperation of online stores and price comparison engines in Poland compared to Ukraine. At the same time, research results allow to state that server security in both countries is on the same rather high level and that online stores use transparent and safe methods of online payment.

Research limitations/implications

This research opens a way to other, expanded observations which will include more countries and larger scopes of data. Its main limitation is that GDPR influence is only studied in two countries, not in all countries where it is implemented.

Originality/value

This research contributes from security and trust perspectives by analyzing the situation in two countries as follows: the EU member (Poland) and a non-EU country (Ukraine). The value of exploring the situation of Ukrainian e-commerce consists of understanding how online stores function without implementing the GDPR. Observation of shopbots application allows drawing an important conclusion of the necessity for online stores to cooperate with such services. It was also revealed that consumers’ trust in both countries depends a lot on the payment methods applied by an online store and on the ease of use of these methods.

Details

Digital Policy, Regulation and Governance, vol. 22 no. 4
Type: Research Article
ISSN: 2398-5038

Keywords

Access Restricted. View access options
Article
Publication date: 21 April 2023

Meenal Arora, Jaya Gupta and Amit Mittal

This study aims to provide insight into consumer behavior regarding the use of food delivery apps when making purchases. To investigate the primary elements affecting users'…

458

Abstract

Purpose

This study aims to provide insight into consumer behavior regarding the use of food delivery apps when making purchases. To investigate the primary elements affecting users' intentions to use meal delivery applications, this study suggests an extension to the technology acceptance model through some contextual variable such as “various food choices (VFC),” “trust (TRR),” “perception of COVID-19-related risks (PCR)” and “convenience (CONV)” during the pandemic.

Design/methodology/approach

A cross-sectional data of 407 was collected in the Indian context. This research adopts the covariance-based structural modeling approach to test the hypotheses along with hierarchical regression to predict the efficiency of constructs.

Findings

Considering the outcomes, “perceived usefulness (PU)” was positively influenced by “perceived ease of use (PEOU),” “VFC” and “CONV.” In addition, the attitude (ATT) was positively impacted by “PU,” “TRR” and “PEOU.” Nevertheless, “PCR” negatively influenced ATT. In additional, this research illustrates the positive impact of ATT and PU on behavioral intention to use.

Originality/value

By confirming the technology acceptance model's capacity for explanation in relation to food delivery apps, this study adds to the body of knowledge. The primary focus of this study is on determining the direct impact of the identified determinants on the adoption of food delivery applications within the context of a pandemic situation in developing countries.

Details

Global Knowledge, Memory and Communication, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2514-9342

Keywords

1 – 10 of 54
Per page
102050