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Article
Publication date: 10 April 2019

Mohammad Amin Jarrahi, Emad Roshandel, Mehdi Allahbakhshi and Mohammad Ahmadi

This paper aims to achieve an optimal design for distribution transformers considering cost and power losses. Particle swarm optimization (PSO) algorithm is used as an…

Abstract

Purpose

This paper aims to achieve an optimal design for distribution transformers considering cost and power losses. Particle swarm optimization (PSO) algorithm is used as an optimization tool for minimizing the objective functions of design procedure which are cost and electrical and iron losses.

Design/methodology/approach

In this paper, distribution transformer losses are considered as operating costs. Also, transformer construction cost which depends on the amount of iron and copper in the structure is assumed as its initial cost. In addition, some other important constraints such as appropriate ranges of transformer efficiency, voltage regulation, temperature rise, no-load current, and winding fill factor are investigated in the design procedure. The PSO algorithm is applied to find optimum amount of needed copper and iron for a typical distribution transformer. Moreover, transformer impedance considered as a constraint to achieve an acceptable voltage regulation in the design process.

Findings

It is shown that the proposed design procedure provides a simple and effective approach to estimate the flux and current densities for minimizing the active part cost and active power losses which means reduction in amount of transformer total owning cost (TOC).

Originality/value

The methodology advances a proposal for reducing distribution transformers costs using PSO algorithm. The approach considers the aforementioned constraints and TOC to minimize the active part cost and maximize the efficiency. It is demonstrated that a designed transformer will not be optimum when the transformer losses over years are not considered in design procedure. Finally, the results prove the effectiveness of the proposed procedure in designing cost-effective distribution transformers from its initial cost until its whole life.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 38 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 13 May 2019

Seyed Abdolkarim Payambarpour, Mohammad Alhuyi Nazari, Mohammad Hossein Ahmadi and Ali J. Chamkha

This study aims to investigate heat and mass transfer in a one-row heat exchanger. The required equations are obtained based on two-dimensional model analysis in a cell of…

Abstract

Purpose

This study aims to investigate heat and mass transfer in a one-row heat exchanger. The required equations are obtained based on two-dimensional model analysis in a cell of the heat exchanger. By using finite difference approach, the obtained equations are solved to determine distribution of temperature and the efficiency of the heat exchanger in the case of partially wet surface. In this research, Lewis Number as unity and water vapor saturation as parabolic are assumed. Obtained results show that increase in thermal conductivity fin leads to decreasing thermal resistance; therefore, temperature changes in radial from center to out of fin are reduced and efficiency of fin increases.

Design/methodology/approach

In this regard, fin material plays a significant role in fin efficiency. Changes in airflow also result in an efficiency increase by temperature and relative humidity, and efficiency is decreased by airflow velocity increase, and these changes are almost linear. Moreover, the fins with more wet surface are more sensitive to changes in fin dimensions and air flow characteristics, and it is a result of conjugate heat transfer mechanism, in which latent heat transfer in the fins with more wet surface has a significant role.

Findings

Thermal property and geometry of the fin under wet conditions play a more important role than the fin under dry conditions. Changes in airflow result in an efficiency increase by temperature and relative humidity, and efficiency is decreased by airflow velocity increase, and these changes are almost linear. Fins with more wet surface are more sensitive to changes in fin dimensions and air flow characteristics.

Originality/value

Effects of the temperature of water supply and mass flow rate were considered in the study. The results had good agreement with actual data.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 10
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 28 August 2019

Abbas Naeimi, Mohammad Hossein Ahmadi, Milad Sadeghzadeh and Alibakhsh Kasaeian

This paper aims to determine the optimum arrangement of a reverse osmosis system in two methods of plug and concentrate recycling.

Abstract

Purpose

This paper aims to determine the optimum arrangement of a reverse osmosis system in two methods of plug and concentrate recycling.

Design/methodology/approach

To compare the optimum conditions of these two methods, a seawater reverse osmosis system was considered to produce fresh water at a rate of 4,000 m3/d for Mahyarkala city, located in north of Iran, for a period of 20 years. Using genetic algorithms and two-objective optimization method, the reverse osmosis system was designed.

Findings

The results showed that exergy efficiency in optimum condition for concentrate recycling and plug methods was 82.6 and 92.4 per cent, respectively. The optimizations results showed that concentrate recycling method, despite a 36 per cent reduction in the initial cost and a 2 per cent increase in maintenance expenses, provides 6 per cent higher recovery and 19.7 per cent less permeate concentration than two-stage plug method.

Originality/value

Optimization parameters include feed water pressure, the rate of water return from the brine for concentrate recycling system, type of SW membrane, feedwater flow rate and numbers of elements in each pressure vessel (PV). These parameters were also compared to each other in terms of recovery (R) and freshwater unit production cost. In addition, the exergy of all elements was analyzed by selecting the optimal mode of each system.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Content available
Article
Publication date: 6 April 2020

Nikta Hatamizadeh, Mohammad Ahmadi, Roshanak Vameghi and Mohammad Ali Hosseini

This paper aims to clear ambiguities regarding the definition of intellectual capital and its components in the evaluation of rehabilitation organizations.

Abstract

Purpose

This paper aims to clear ambiguities regarding the definition of intellectual capital and its components in the evaluation of rehabilitation organizations.

Design/methodology/approach

A preliminary definition of intellectual capital and its three domains of human, relational and structural capital and separate lists of proposed components for each domain was developed based on the results of a previous study. Fourteen experts in rehabilitation, health management and management engaged in Delphi rounds to reach agreed-upon definitions. Their ideas on relevance and the measurements of each proposed component in the assessment of intellectual capital in rehabilitation organizations were gathered by a questionnaire.

Findings

Intellectual capital was defined as “The capital that emerges from the interaction of human resources’ ‘ability to think’ and to ‘create ideas’ with ‘a favorable internal and external organizational environment’ (including the managerial, social, structural, and physical environment, as well as communication between the inside and outside of the organization).” This capital is expected to gradually increase with further education, skills training and the gaining of experience by staff and managers. Also, the further development of intra-organizational structures and inter-relations with the market will empower the organization to adapt to continually changing circumstances, leading to competitive value and profit. Finally, a list of 101 proposed components was agreed upon in the evaluation of intellectual capital in rehabilitation organizations.

Originality/value

This paper may lead to the development of measurement tools and ultimately to planning effective programs to increase intellectual capital in rehabilitation organizations.

Details

Journal of Health Research, vol. 34 no. 3
Type: Research Article
ISSN: 2586-940X

Keywords

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Article
Publication date: 19 June 2019

Seyed Hamid Delbari, Amir Nejat, Mohammad H. Ahmadi, Ali Khaleghi and Marjan Goodarzi

This study aims to carry out numerical modeling to predict aerodynamic noise radiation from four different Savonius rotor blade profile.

Abstract

Purpose

This study aims to carry out numerical modeling to predict aerodynamic noise radiation from four different Savonius rotor blade profile.

Design/methodology/approach

Incompressible unsteady reynolds-averaged navier-stokes (URANS) approach using gamma–theta turbulence model is conducted to obtain the time accurate turbulent flow field. The Ffowcs Williams and Hawkings (FW-H) acoustic analogy formulation is used for noise predictions at optimal tip speed ratio (TSR).

Findings

The mean torque and power coefficients are compared with the experimental data and acceptable agreement is observed. The total and Mono+Dipole noise graphs are presented. A discrete tonal component at low frequencies in all graphs is attributed to the blade passing frequency at the given TSR. According to the noise prediction results, Bach type rotor has the lowest level of noise emission. The effect of TSR on the noise level from the Bach rotor is investigated. A direct relation between angular velocity and the noise emission is found.

Practical implications

The savonius rotor is a type of vertical axis wind turbines suited for mounting in the vicinity of residential areas. Also, wind turbines wherein operation are efficient sources of tonal and broadband noises and affect the inhabitable environment adversely. Therefore, the acoustic pollution assessment is essential for the installation of wind turbines in residential areas.

Originality/value

This study aims to investigate the radiated noise level of four common Savonius rotor blade profiles, namely, Bach type, Benesh type, semi-elliptic and conventional. As stated above, numbers of studies exploit the URANS method coupled with the FW-H analogy to predict the aeroacoustics behavior of wind turbines. Therefore, this approach is chosen in this research to deal with the aeroacoustics and aerodynamic calculation of the flow field around the aforementioned Savonius blade profiles. The effect of optimal TSR on the emitted noise and the contribution of thickness, loading and quadrupole sources are of interest in this study.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 January 2000

Mohammad Ahmadi, Marilyn M. Helms and Tammy J. Ross

This paper examines the concept and the implementation of telecommuting and how it will affect the employee, organization and the general business environment. It also…

Abstract

This paper examines the concept and the implementation of telecommuting and how it will affect the employee, organization and the general business environment. It also provides suggestions for employers implementing a telecommuting program. In this new millennium, it is obvious that the workforce and the way of work are changing drastically. Telecommuting, or allowing the employees to perform their jobs away from the central or primary business location, is increasing. While many jobs have some aspects that may lend themselves to telecommuting, white‐collar jobs that require a great amount of independent work are the most suitable for telecommuting. The paper also discusses the importance of selecting the right employees for telecommuting.

Details

Facilities, vol. 18 no. 1/2
Type: Research Article
ISSN: 0263-2772

Keywords

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Article
Publication date: 28 October 2013

Mohammad Ahmadi, Parthasarati Dileepan and Sarla R. Murgai

The purpose of this study is to develop a mathematical model that can be used to forecast the demand for the inter-library loan (ILL) requests. Accurate estimates of…

Abstract

Purpose

The purpose of this study is to develop a mathematical model that can be used to forecast the demand for the inter-library loan (ILL) requests. Accurate estimates of demand are valuable for assisting researchers in their research endeavors.

Design/methodology/approach

Data were gathered at the University of Tennessee at Chattanooga for a period of 48 months from July 2008 to the end of June of 2012. Using these data, a centered moving average with seasonal variation model was formulated for forecasting the demand for the inter-library loan. These forecasts were then compared with the actual values to determine the accuracy of prediction.

Findings

Centered moving average with seasonal variation model proved to be a good predictor of the demand for the inter-library loans. The model proved to be a very good forecasting tool as the actual values seem to follow the forecasts very closely.

Originality/value

It is very important to be able to forecast the demand for the inter-library loans. Researchers constantly demand material for their research and librarians try to fulfill their demands. If the demand can be forecast with some degree of accuracy, the process can be expedited.

Details

The Bottom Line, vol. 26 no. 3
Type: Research Article
ISSN: 0888-045X

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Article
Publication date: 23 November 2012

Mohammad Ahmadi, Parthasarati Dileepan and Sarla R. Murgai

The purpose of this paper is to examine the advantages of developing a simulation model of the activities of a university library, in order to balance the available…

Abstract

Purpose

The purpose of this paper is to examine the advantages of developing a simulation model of the activities of a university library, in order to balance the available resources with demand for services. Meeting the demand is an essential part of managing a modern library. Inadequate levels of resources will result in excessive waiting times for the patrons.

Design/methodology/approach

A simulation modeling approach is undertaken and the library activities of the University of Tennessee at Chattanooga (UTC) are simulated. Simulation modeling is an invaluable tool to understand the resource usage patterns and making intelligent budgeting choices. In the epoch of severe budget cuts, available financial resources must be carefully allocated where there is a critical need. Such a simulation modeling of the critical operations of an academic library of a campus upward of 11,000 students is presented in this study.

Findings

A simulation model of the arrivals, flow, and usage patterns of library resources by the patrons described in this research, determined that there were four critical resources: the number of reference librarians, the number of checkout assistants, the number of computers, and the number of electronic gadgets. This study illustrates the need for careful analysis of arrival of patrons, resource levels, and resource usage with the objective of developing a resource level decision strategy that will result in an optimal level of resource usage by patrons.

Practical implications

With the application of simulation models, it is possible to determine the needs for the limited resources at the library and coordinate the availability of the resources with the needs.

Originality/value

Research in the use of simulation models for the determination of the resource levels that are best suited for an anticipated level of patron arrivals in the libraries is limited at best. This research adds value by providing information to fill this dearth of literature. The results of the simulation provided in this study can be used to develop budget priorities and to validate those priorities.

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Article
Publication date: 1 March 1989

Mohammad Ahmadi, Thomas A. Gavin and Edson G. Hammer

Factor analysis reveals the job satisfaction profiles for internalauditors and industrial accountants have some marked differences. Thesedifferences in the context of…

Abstract

Factor analysis reveals the job satisfaction profiles for internal auditors and industrial accountants have some marked differences. These differences in the context of roles and working environments are discussed and suggestions are made as to how this type of information can be used constructively by management.

Details

Managerial Auditing Journal, vol. 4 no. 3
Type: Research Article
ISSN: 0268-6902

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Article
Publication date: 22 August 2008

Mohammad Ahmadi, Parthasarati Dileepan, Sarla R. Murgai and Wendy Roth

The purpose of this study is to develop a mathematical model that can be used to forecast the number of individuals who enter the library as well as the number of patrons…

Abstract

Purpose

The purpose of this study is to develop a mathematical model that can be used to forecast the number of individuals who enter the library as well as the number of patrons that seek assistance at the reference desk of the library. An accurate estimate of demand at the reference desk is valuable for effective staffing decisions.

Design/methodology/approach

An exponential smoothing model (Winter's model) was developed for forecasting. Data were gathered at the University of Tennessee at Chattanooga for an entire year. Using these data, an exponential smoothing model was formulated for forecasting the number of patrons seeking assistance. Since the data showed no trend but the presence of two seasonality factors, one for the week‐of‐the‐semester effect and one for the day‐of‐the‐week effect, the Winter's method appeared to be best suited. The Winter's method develops a formula from the data and allows the formula to be continuously fine‐tuned as new observations come in day after day.

Findings

The modified Winter's exponential smoothing model proved to be a good predictor of the number of patrons seeking assistance. In spite of large natural random variability present in the data, the actual values seem to follow the forecasts very closely.

Originality/value

It is vital to be able to forecast the number of clients at the reference desk that seek assistance per day. The modified exponential smoothing model is a valuable tool for such forecasting.

Details

The Bottom Line, vol. 21 no. 2
Type: Research Article
ISSN: 0888-045X

Keywords

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