COMPARATIVE ANALYSIS OF TURBULENCE MODELS FOR AUTOMOTIVE AERODYNAMIC SIMULATION AND DESIGN

Dastan Igali,Olzhas Mukhmetov,Yong Zhao,Sai Cheong Fok,Soo Lee Teh 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.6

The reduction of energy consumption and environmental impacts of road vehicles is always a major design objective. Many investigations suggest that reducing aerodynamic drags such as pressure drag and skin friction drag is a more efficient method than engine modification in achieving the design objective. Turbulent flow around a bluff body is notoriously difficult to simulate accurately due to the complexity of the flow conditions around the body, such as complex flow separation and laminar to turbulent flow transition. This paper investigates the flow over a benchmark model called the Ahmed body with a slant angle of 25o, which is considered a challenging problem for RANS approach with two-equation turbulence models (Menter, 1994; Serre et al., 2013). Three popular turbulence models, such as the k-ε, k-ω and SST models are evaluated by benchmarking their predictions against experimental data and those of the latest LES solvers. The main purpose of the study is to compare the performances of these models in simulating such a category of flows. In addition, the accuracy and factors that determine the success of such simulation are discussed. Our findings, for the first time, show that with a skillfully generated mesh and proper discretization schemes, the RANS approach with the above two-equation turbulence models are capable of capturing the salient features of the highly complex flow over the Ahmed body with a slant angle of 25o. The performances are as good as the LES solvers as reported in Serre et al. (2013), if not better for time-averaged flow simulations. The SST model produces the best results among the three models studied. This study could assist designers in the automotive industry in the applications of these cost-effective tools to improve their design productivity. Future study will focus on the performances of the models in simulating time-dependent flows over the Ahmed body.

Psychoeducation Intervention to Improve Adjustment to Cancer among Turkish Stage I-II Breast Cancer Patients: A Randomized Controlled Trial

Dastan, Nihal Bostanci,Buzlu, Sevim Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.10

Psycho-educational interventions are not a substitute for analgesics, but they may serve as adjuvant therapy. Nurses can provide psychoeducational programmes to cancer patients to assist them in optimizing behavior that strengthen adjustment. The aim here was to determine the effects of psychoeducation on levels of adjustment to cancer in stage I-II breast cancer patients who met the study criteria (experimental group: 38 women, control group:38 women). The psychoeducational program consisted of eight 90 minute weekly sessions and data were collected using a questionnaire and the Mental Adjustment to Cancer Scale three times: before, six weeks and six months after the intervention. Data analysis was performed using descriptive statistical methods as well as the Chi square test, the Mann Whitney U test, repeated measures analysis of variance, the matched pairs t test and the Post Hoc Bonferroni test. The results at 6 weeks and 6 months after the program revealed that the experimental group had higher levels of "fighting spirit", lower levels of "helplessness/hopelessness, anxious preoccupation and fatalism" but there was no significant change in levels of "avoidance/denial" compared to the control group with regard to adjustment to cancer. In this study, psychoeducation was shown to cause positive changes in levels of adjustment to cancer in breast cancer patients

Korean Expatriates Adjustments and Job Satisfaction in Malaysia: Analysis of Corporate Cultural Asymmetry

Omkar Dastane,Woo Yong Willis Lee 한국유통과학회 2016 The Journal of Industrial Distribution & Business( Vol.7 No.4

Purpose - The purpose of this study is to discover how Korean expatriates that are currently employed in Korean subsidiaries operational in Malaysia possibly suffer from career dissatisfaction due to differences between Korean Corporate Culture (KCC) and Malaysian Corporate Culture (MCC). The integration of KCC into MCC is discussed. Research design, data, and methodology – The analysis herein is via a qualitative research. Forty-six interviewees voluntarily participated in in-depth interviews. Document analysis and qualitative interviews were utilized to develop participant profiles and to generate the framework. Interview data were transcribed and subsequently analysed to facilitate the development of themes and ultimately led to emerging patterns. The framework discusses the following Confucian pillars pronounced in KCC: Control Systems, Power Structures, Organisational Structures, Authority and Harmony and Stories and Myths. Those pillars are analysed and the results of the interviews are discussed in detail. Results – Korean expatriates on assignment in Malaysia endure struggles in all five selected Confucian pillars as they are not symmetrical with Korean Corporate Culture common at head companies in Korea. Conclusion - As a consequence, there is substantial disharmony which needs to be rectified if Korean companies are to continue their ‘miraculous’ economic movement into the country.

A comparative analysis of sheeting die geometries using numerical simulations

Igali, Dastan,Wei, Dongming,Zhang, Dichuan,Perveen, Asma Techno-Press 2020 Advances in computational design Vol.5 No.2

The flow behavior of polymer melts within a slit die is an important consideration when designing a die geometry. The quality of the extruded polymer product can be determined through an evaluation of the flow homogeneity, wall shear rate and pressure drop across the central height of the die. However, mathematical formulations cannot fully determine the behavior of the flow due to the complex nature of fluid dynamics and the nonlinear physical properties of the polymer melts. This paper examines two slit die geometries in terms of outlet velocity uniformity, shear rate uniformity at the walls and pressure drop by using the licensed computational fluid dynamics package, Ansys POLYFLOW, based on the finite element method. The Carreau-Yasuda viscosity model was used for the rheological properties of the polypropylene. Comparative analysis of the simulation results will conclude that the modified die design performs better in all three aspects providing uniform exit velocity, uniform wall shear rates, and lower pressure drop.

Combined Antimicrobial Activity of Extracts from Quercus infectoria Galls and Scrophularia striata Aerial Parts for an Anticariogenic Herbal Mouthwash

Falakdin Pooya,Dastan Dara,Pourmoslemi Shabnam 대한약침학회 2023 Journal of pharmacopuncture Vol.26 No.1

Objectives: Dental caries is one of the most prevalent human diseases worldwide. The disease initiates with bacterial adherence to the tooth surface followed by the formation of dental plaques. Mutans streptococci and Candida albicans are principal oral microorganisms involved in the initiation and development of dental caries. Phytochemicals have been shown to possess promising antimicrobial properties against a wide range of microorganisms and can be used for the prevention and treatment of dental caries. Herein, we reviewed literature on plants that are traditionally used for their antimicrobial properties or possess promising anticariogenic activity. We selected aerial parts of Scrophularia striata (S. striata) and galls of Quercus infectoria (Q. infectoria) and investigated their antimicrobial activity against cariogenic microorganisms. Methods: Water soluble fractions were obtained from hydroalcoholic extracts of S. striata and Q. infectoria and their antimicrobial activity against Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus), and Candida albicans (C. albicans) was evaluated separately and in combination. The extracts were then used for preparing an herbal mouthwash whose stability and tannic acid content were evaluated over 60 days. Results: Q. infectoria gall extract possesses efficient antimicrobial activity that was synergistically enhanced in the presence of S. striata extract. Mouthwash prepared using these extracts showed desirable organoleptic characteristics, antimicrobial activity, and stability. Conclusion: Extracts of S. striata and Q. infectoria galls can be used together for preparing dental products with effective anticariogenic properties. Our study highlights the importance of extensive pharmacological investigations when using herbal products alone or in combination with other chemical substances.

The Impact of Technology Adoption on Organizational Productivity

Monika LAKHWANI,Omkar DASTANE,Nurhizam Safie Mohd SATAR,Zainudin JOHARI 한국유통과학회 2020 The Journal of Industrial Distribution & Business( Vol.11 No.4

Purpose: This research investigates the impact of technology adoption on organisation productivity. The framework has three independent variables viz. technological change, information technology (IT) infrastructure, and IT knowledge management and one dependent variable as organisational productivity. Research design, data and methodology: An explanatory research design with a quantitative research method was employed, and data was collected using a self-administered questionnaire using online as well as an offline survey. The sample consisted of 300 IT managers and senior-level executives (production as well as service team) in leading IT companies in Malaysia selected using snowball sampling. Normality and reliability assessment was performed in the first stage utilising SPSS 22, and Confirmatory Factory Analysis (CFA) was performed with maximum likelihood estimation to assess the internal consistency, convergent validity, and discriminant validity. Finally, Structural Equation Model (SEM) and path analysis are conducted using AMOS 22. Results: The research findings demonstrated that technological change and IT infrastructure positively and significantly impact the organisation's productivity while IT knowledge management has significant but negative impact on organizational productivity of IT companies in Malaysia. Conclusion: The research concludes that all three factors plays important role in deciding organizational producvity. Recommendations, implications, limitations and future research avenues are discussed.

Key Factors Affecting Intention to Order Online Food Delivery (OFD)

SAN, Sing Su,DASTANE, Omkar Korea Distribution Science Association 2021 The Journal of Industrial Distribution & Business( Vol.12 No.2

Purpose: This study investigated the impact of key factors such as service quality, perceived benefit and brand familiarity on a consumer's intention to order online food delivery (OFD). In addition, mediating effect of electronic word of mouth (e-WOM) between relationships among selected key variables and OFD purchase intention is also assessed. Research design, data and methodology: This explanatory, quantitative study employed convenience sampling and collected data through online structured questionnaire from 304 respondents who are users of OFD apps based in greater Klang valley region of Malaysia. The data was then subjected to normality and reliability assessment followed by confirmatory factor analysis, validity assessment and structural equation modelling using IBM SPSS AMOS 24.0. Results: Findings revealed that service quality, perceived benefits and brand familiarity affects purchase intention positively and significantly. Perceived benefits demonstrated highest impact on purchase intention followed by brand familiarity and service quality. Findings also suggest that e-WOM fully mediates relationship between brand familiarity and purchase intention, however, the same was not observed for remaining two variables. Conclusions: The study has enriched OFD literature by investigating impact of selected key factors on purchase intention in the context of OFD. Implications, limitations and future research avenues are then discussed.

A critical review on intrinsic conducting polymers and their applications

Navid Nasajpour-Esfahani,Davoud Dastan,As’ad Alizadeh,Pouria Shirvanisamani,Mohammadreza Rozati,Eden Ricciardi,Bo Lewis,Ashish Aphale,Davood Toghraie 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.125 No.-

In the last two decades, conductive polymer (CPs) materials have replaced metals and semiconductors ina variety of commercial applications, including energy storage and conversion, biomedical devices suchas drug delivery and bioactuators, and electronic devices such as sensors, due to their superior electricaland electrochemical properties. Therefore, researchers have paid a great deal of attention to CPs in orderto investigate new fundamental structures synthesized via diverse methods. In addition, the invention ofnanomaterials has instigated the improvement of different properties of CPs, such as electrical, chemical,flexible structure, and tunable conductivity features. This paper aims to review the electrical and electrochemicalconductivity mechanism of CPs and overview the common CPs with excellent electrical properties. Moreover, the current research discusses different synthesis methods used to prepare CPs. Furthermore, the effect of various carbon nanofillers on the electrical properties of CPs and the variousfactors affecting the electrical conductivity of CPs are examined in depth. In conclusion, the most recentapplications and prospective aspects of CPs are investigated to demonstrate their remarkable potentialfeatures among metals and semiconductors.

Building a Sustainable Competitive Advantage for Multi-Level Marketing (MLM) Firms: An Empirical Investigation of Contributing Factors

Lee Siew Keong,Omkar Dastane 한국유통과학회 2019 유통과학연구 Vol.17 No.3

Purpose - The purpose of this research is to investigate the factors contributing to sustainable competitive advantage for multi-level marketing (MLM) firms in Malaysia. The selected variables in this study are company image, product innovation, leadership, distributor rewards system and distributor training system. Research design, data, and methodology - Quantitative research method is employed with collected sample size of 398 respondents using judgmental sampling technique. Normality and reliability test were performed in the first stage utilizing SPSS 22 and Confirmatory Factory Analysis (CFA) and variance analysis were obtained in the subsequent stage, following up with the overall fit of the measurement model, Structural Equation Model (SEM) using AMOS 22 with maximum likelihood estimation to assess the internal consistency, convergent validity and discriminant validity. Results - The research findings show that company image, leadership, distributor rewards system and distributor training system were supported and are factors affecting the sustainable competitive advantage of MLM companies in Malaysia. However, in this study, product innovation was not supported but this result does not depict that it is trivial and inconsequential in maintain sustainable advantage. Conclusion - Companies can build sustainable competitive advantage by focusing on these contributing factors. Several other comments and implications were brought to light and discussed in the paper.

The Impact of Word of Mouth on Customer Perceived Value for the Malaysian Restaurant Industry

Adebusoye Shedrack Oluwafemi,Omkar Dastane 한국유통과학회 2016 Asian Journal of Business Environment (AJBE) Vol.6 No.3

Purpose - The purpose of this research is to determine the impact of word of mouth on customer perceived value for restaurants in Malaysia. The objectives of this research include determining how word of mouth (WoM) factors - frequency of word of mouth messages, reputation of word of mouth messenger, richness of word of mouth message, dispersion of word of mouth conversations and manner of word of mouth delivery impact customer perceived value in Malaysian restaurant industry. Research Design, Data, and Methodology – The research follows causal / explanatory research method based on quantitative data. A sample of 150 restaurant customers in Kuala Lumpur, Malaysia was selected using convenience sampling technique. Likert scale questionnaire is used to collect data and data is analysed using regression analysis through SPSS 22. Results – The statistical analysis revealed that independent variable ‘manner of delivery’ significantly and positively impacts c ustomer perceived value for restaurants in Malaysia. Conclusions – To build strong positive customer perception, Malaysian restaurants can enhance word of mouth campaigns’ ‘manner of delivery’ by making them passionate, exciting and with high emotional appeal.