Probabilistic multi-objective optimization of a corrugated-core sandwich structure

Khalkhali, Abolfazl,Sarmadi, Morteza,Khakshournia, Sharif,Jafari, Nariman Techno-Press 2016 Geomechanics & engineering Vol.10 No.6

Corrugated-core sandwich panels are prevalent for many applications in industries. The researches performed with the aim of optimization of such structures in the literature have considered a deterministic approach. However, it is believed that deterministic optimum points may lead to high-risk designs instead of optimum ones. In this paper, an effort has been made to provide a reliable and robust design of corrugated-core sandwich structures through stochastic and probabilistic multi-objective optimization approach. The optimization is performed using a coupling between genetic algorithm (GA), Monte Carlo simulation (MCS) and finite element method (FEM). To this aim, Prob. Design module in ANSYS is employed and using a coupling between optimization codes in MATLAB and ANSYS, a connection has been made between numerical results and optimization process. Results in both cases of deterministic and probabilistic multi-objective optimizations are illustrated and compared together to gain a better understanding of the best sandwich panel design by taking into account reliability and robustness. Comparison of results with a similar deterministic optimization study demonstrated better reliability and robustness of optimum point of this study.

Effects of Antibiotic Consumption on Children 2-8 Years of Age Developing Asthma

Hamid Reza Khalkhali,Sima Oshnouei,Shaker Salarilak,Mohammadhossein Rahimi Rad,Mohammad Karamyar,Javad Khashabi 한국역학회 2014 Epidemiology and Health Vol.36 No.-

OBJECTIVES: Antibiotic exposure in children is a possible contributor to the increasing asthma prevalence in several countries. The present study aimed to investigate the association between antibiotic exposure and the risk of developing childhood asthma at 2-8 years of age. METHODS: A case-control study was undertaken among children aged 2-8 years old between March and September 2010 in the Urmia district in the northwest of Iran. The cases were doctor-diagnosed asthmatic children based on Global Initiative for Asthma criteria (n=207), and the controls were children without respiratory symptoms (n=400) selected by frequency matching by age and gender. Clinical data including antibiotic exposure was collected by a validated and reliable questionnaire, which was completed by interviewing parents/guardians. RESULTS: Antibiotic consumption during the first year of life increased the odds ratio [OR] of asthma symptoms at 2-8 years of age (crude OR, 2.26; 95% confidence interval [CI], 1.53-3.35; p<0.01), and the strength of association was similar after adjusting for a family history of asthma or atopic disorder, preterm delivery, birth order, and delivery method (adjusted OR, 1.91; 95% CI, 1.27-2.88; p=0.03). CONCLUSIONS: Our study suggests that antibiotic consumption in children was associated with an increased risk of childhood asthma, and an additional confirmative study is needed.

Periodic Virtual Hierarchy: A Trust Model for Smart Grid Devices

Arezou Moussavi-Khalkhali,Ram Krishnan,Mo Jamshidi 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.11

Authentication among various devices that form a smart grid is a fundamental issue. Due to the large-scale, distributed, and heterogeneous nature of a smart grid, authenticating devices based on their credentials such as secret keys is often not practical. Alternatively, certificate-based trust relationships can facilitate interactions in such scenarios. Two pivotal trust relationship models, hierarchical and peer-to-peer, have been well-researched in the literature. However, the devices in a smart grid do not benefit exclusively from a single trust relationship model owing to the heterogeneous nature of its control structure. In this paper, we propose a periodic hierarchical trust relationship model suitable for real-time applications in a smart grid and robust to the single point of failure problem, which is common in hierarchies. The proposed model deploys a two-layer security authentication mechanism among different devices within those domains in which there are control hierarchies using short-term and long-term certificates, the latter of which is verified periodically.

Development and Validation of a Safety Climate Scale for Manufacturing Industry

Ghahramani, Abolfazl,Khalkhali, Hamid R. Occupational Safety and Health Research Institute 2015 Safety and health at work Vol.6 No.2

Background: This paper describes the development of a scale for measuring safety climate. Methods: This study was conducted in six manufacturing companies in Iran. The scale developed through conducting a literature review about the safety climate and constructing a question pool. The number of items was reduced to 71 after performing a screening process. Results: The result of content validity analysis showed that 59 items had excellent item content validity index (${\geq}0.78$) and content validity ratio (> 0.38). The exploratory factor analysis resulted in eight safety climate dimensions. The reliability value for the final 45-item scale was 0.96. The result of confirmatory factor analysis showed that the safety climate model is satisfactory. Conclusion: This study produced a valid and reliable scale for measuring safety climate in manufacturing companies.

Development and Validation of a Safety Climate Scale for Manufacturing Industry

Abolfazl Ghahramani,Hamid R. Khalkhali 한국산업안전보건공단 산업안전보건연구원 2015 Safety and health at work Vol.6 No.2

Background: This paper describes the development of a scale for measuring safety climate. Methods: This study was conducted in six manufacturing companies in Iran. The scale developed through conducting a literature review about the safety climate and constructing a question pool. The number of items was reduced to 71 after performing a screening process. Results: The result of content validity analysis showed that 59 items had excellent item content validity index (? 0.78) and content validity ratio (> 0.38). The exploratory factor analysis resulted in eight safety climate dimensions. The reliability value for the final 45-item scale was 0.96. The result of confirmatory factor analysis showed that the safety climate model is satisfactory. Conclusion: This study produced a valid and reliable scale for measuring safety climate in manufacturing companies.

Optimal design of the floor panel for an automotive platform under uncertainty of the vehicle length

Lahijani, Abdolah Tavakoli,Shojaeefard, M.H.,Khalkhali, Abolfazl Techno-Press 2018 Geomechanics & engineering Vol.14 No.1

Length of a vehicle is an important variation to generate different variants of an automotive platform. This parameter is usually adjusted by embedding dimensional flexibility into different components of the Body in White (BIW) including the floor pan. Due to future uncertainties, it is not necessarily possible to define certain values of wheelbase for the future products of a platform. This work is performed to add flexibility into the design process of a length-variable floor pan. By means of this analysis, the cost and time consuming process of optimization is not necessary to be performed for designing the different variants of a product family. Stiffness and mass of the floor pan are two important functional requirements of this component which directly affect the occupant comfort, dynamic characteristics, fuel economy and environmental protection of the vehicle. A combination of Genetic algorithm, GMDH-type of artificial neural networks and TOPSIS methods is used to optimally design the floor pan associated with arbitrary length of the variant in the defined system range. The correlation between the optimal results shows that for a constant mass of the floor pan, the first natural frequency decreases by increasing the length of this component.

Comparative Analysis of the Perception of Family Functioning by Heads of Families with and without Cancer Members During Illness

Sahebihagh, Mohamad Hasan,Amani, Leila,Salimi, Saleh,Feizi, Aram,Khalkhali, Hamid Reza,Atri, Shirin Barzanjeh Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.9

Background: Cancer is a major health problem due to the aging population with increasing deaths. Family functioning is affected by cancer diagnosis and treatment. The aim of this study was to comparative analysis of the perception of family functioning by heads of families with and without cancer members during illness, focusing on changes or probable changes. Materials and Methods: This comparative study was conducted on two groups (families with a member of the cancer and controls without a family member with cancer). The families were of patients referred to the clinics and hospitals of Imam Khomeini, Taleghani and Omid of Urmia city, the number of samples being 148 for cases and 176for the control group. To collect the data, valid and reliable family functioning (FAD) was applied, a 60-item questionnaire with seven dimensions, with heads of families. To analyze the data SPSS- 23 Software was used for descriptive and analytical statistics. Significance level was defined p <0.05. Results: Among the seven items : problem solving, communication, roles, emotional response, emotional involvement, behavior control and overall functioning, only differences for average scores of problem-solving were statistically significant. Discussion: Contrary to common perception of severe damage for family functioning in families with cancer members, results of this study indicate that functioning in terms of family caregivers is more or less similar to that of the families with other diseases. Only in problem-solving item do these families experience more difficulty. Conclusion: According to the research findings, in nursing from families with cancer patient, it is recommended to focus more on the problem-solving item of the families.