The effect of embedding a porous core on the free vibration behavior of laminated composite plates

Babak Safaei 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.5

This paper proposes the use of a porous core between layers of laminated composite plates to examine its effect on the natural frequencies of the resulted porous laminated composite sandwich plate (PLCSP) resting on a two-parameter elastic foundation. Moreover, it has been suggested that the dispersion of porosity has two different functionally graded (FG) patterns which are compared with a uniformly dispersed (UD) profile to find their best vibrational efficiency in the proposed PLCSPs. In FG patterns, two types of dispersions, including symmetric (FG-S) and asymmetric (FG-A) patterns have been considered. To derive the governing Eigen value equation of such structures, the first order shear deformation theory (FSDT) of plates has been employed. Accordingly, a finite element method (FEM) is developed to solve the derived Eigen value equation. Using the mentioned theory and method, the effects of porosity parameters, fiber orientation of laminated composite, geometrical dimensions, boundary conditions and elastic foundation on the natural frequencies of the proposed PLCSPs have been studied. It is observed that embedding porosity in core layer leads to a significant improvement in the natural frequencies of PLCSPs. Moreover, the natural frequencies of PLCSPs with FG porous core are higher than those with UD porous core.

An efficient method for reliable optimum design of trusses

Babak Dizangian,Mohammad Reza Ghasemi 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.5

This paper introduces a new and effective design amplification factor-based approach for reliable optimum design of trusses. This paper may be categorized as in the family of decoupled methods that aiming for a reliable optimum design based on a Design Amplification Factor (DAF). To reduce the computational expenses of reliability analysis, an improved version of Response Surface Method (RSM) was used. Having applied this approach to two planar and one spatial truss problems, it exhibited a satisfactory performance.This paper introduces a new and effective design amplification factor-based approach for reliable optimum design of trusses. This paper may be categorized as in the family of decoupled methods that aiming for a reliable optimum design based on a Design Amplification Factor (DAF). To reduce the computational expenses of reliability analysis, an improved version of Response Surface Method (RSM) was used. Having applied this approach to two planar and one spatial truss problems, it exhibited a satisfactory performance.

In vitro evaluation of the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with composite fillings after cyclic loading

Babak Fallahi Sichani,Somayeh Allahyari,Moha Javad Kharazi Fard,Farideh Geramipanah,Leyla Sadighpour 대한치과보철학회 2014 The Journal of Advanced Prosthodontics Vol.6 No.4

PURPOSE There is insufficient data regarding the durability of porcelain laminate veneers bonded to existing composite fillings. The aim of the present study was to evaluate the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with existing composite fillings. MATERIALS AND METHODS Thirty maxillary central incisors were divided into three groups (for each group, n=10): intact teeth (NP), teeth with class III composite fillings (C3) and teeth with class IV cavities (C4). Porcelain laminate veneers were made using IPS-Empress ceramic and bonded with Panavia F2 resin cement. The microleakage of all of the specimens was tested before and after cyclic loading (1 × 106 cycles, 1.2 Hz). The fracture resistance values (N) were measured using a universal testing machine, and the mode of failure was also examined. The statistical analyses were performed using one-way ANOVA and Tukey post hoc tests (α=.05). RESULTS There was a significant difference in the mean microleakage of group C4 compared with group NT (P=.013). There was no significant difference in the fracture loads among the groups. CONCLUSION The microleakage and failure loads of porcelain laminate veneers bonded to intact teeth and teeth with standard class III composite fillings were not significantly different.

A new interleaved high step up converter with low voltage stress on the main switches

Babak Tohidi,Majid Delshad,Hadi Saghafi 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.4

In this paper, a new interleaved high step-up converter with low voltage stress on the switches is proposed. In the proposed converter, soft switching is provided for all switches by just one auxiliary switch, which decreases the conduction loss of auxiliary circuit. Also, the auxiliary circuit is expanded on the converter with more input branches. In the converter all main switches operate under zero voltage switching condition and auxiliary switch operate under zero current switching condition. Because of the interleaved structure, the reliability of converter increases and input current ripples decreases. The clamp capacitor in the converter not only absorb the voltage spikes across the switch due to leakage inductance, but also improve voltage gain. The proposed converter is fully analyzed and to verify the theoretical analysis, a 100 W prototype was implemented. Also, to show the effectiveness of auxiliary circuit on conduction EMI, EMI of the proposed converter comprised with hard switching counterpart.

Evaluation of Bone Mineral Status in Adolescent Idiopathic Scoliosis

Babak Pourabbas Tahvildari,Mohammad-Ali Erfani,Hormoz Nouraei,Mohammad Sadeghian 대한정형외과학회 2014 Clinics in Orthopedic Surgery Vol.6 No.2

Background: Several reports have suggested low bone mineral density (BMD) in patients with adolescent idiopathic scoliosis (AIS). We determined bone mineral status in patients with AIS to evaluate the effect of brace treatment on BMD. Methods: BMD was measured in 46 patients (mean age, 17.8 ± 4.9 years) with AIS (17 with brace and 29 without brace) by dual-energy X-ray absorptiometry scan and compared the results to an age-matched (mean age, 16.6 ± 3.9 years) control group (n = 54). Results: The AIS group had significantly lower bone mass at the lumbar spine (Z-score, –1.500 vs. –0.832) and hip (Z-score, –1.221 vs. –0.754) except at the femoral neck. No difference in BMD was found between patients with AIS who used a brace and those who did not. Conclusions: The results confirmed that BMD was low in AIS patients and it was not affected by brace treatment

Development and Psychometric Properties of an Extended Theory of Planned Behavior Questionnaire for Childbearing Intentions and Behaviors in Iran

Babak Moeini,Amir Erfani,Majid Barati,Amin Doosti-Irani,Hatam Hosseini,Mokhtar Soheylizad 대한가정의학회 2023 Korean Journal of Family Medicine Vol.44 No.2

Background: Childbearing is the most important determinant of population fluctuations, and its study is more im-portant than other population phenomena. Owing to the lack of a valid questionnaire based on the extended theo-ry of planned behavior, this mixed-method study was conducted to determine the validity and reliability of a ques-tionnaire designed to examine related belief-based factors on the intention to bear children in Iranian society.Methods: This study was conducted in two phases in Hamadan city, western Iran, in 2021. Phase 1 consisted of an extensive literature review and a qualitative study using a directed content analysis approach to generate an item pool. Psychometrics were measured in phase 2, including content, face, and construct validity. Reliability was as-sessed based on internal consistency and stability. The collected data were analyzed using IBM SPSS and AMOS ver. 24.0.Results: Mean content validity ratio and content validity index were 0.7 and 0.85, respectively. Exploratory factor analysis of the 32 items identified an eight-factor solution. These factors jointly accounted for 79.1% of the observed variance in the outcome variables. Confirmatory factor analysis indicated a good fit for the data. The internal con-sistency based on Cronbach’s α was 0.85 (0.71–0.93). In addition, stability was confirmed using the test-retest method and intraclass correlation coefficient (0.74–0.94).Conclusion: The designed questionnaire is a valid and reliable instrument for evaluating related belief-based fac-tors on the intention and behavior of childbearing among married men and women in Iran.

Analysis and Implementation of a New Single Switch, High Voltage Gain DC-DC Converter with a Wide CCM Operation Range and Reduced Components Voltage Stress

Babak Honarjoo,Seyed M. Madani,Mehdi Niroomand,Ehsan Adib 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper presents a single switch, high step-up, non-isolated dc-dc converter suitable for renewable energy applications. The proposed converter is composed of a coupled inductor, a passive clamp circuit, a switched capacitor and voltage lift circuits. The passive clamp recovers the leakage inductance energy of the coupled inductor and limits the voltage spike on the switch. The configuration of the passive clamp and switched capacitor circuit increases the voltage gain. A wide continuous conduction mode (CCM) operation range, a low turn ratio for the coupled inductor, low voltage stress on the switch, switch turn on under almost zero current switching (ZCS), low voltage stress on the diodes, leakage inductance energy recovery, high efficiency and a high voltage gain without a large duty cycle are the benefits of this converter. The steady state operation of the converter in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is discussed and analyzed. A 200W prototype converter with a 28V input and a 380V output voltage is implemented and tested to verify the theoretical analysis.

How to Write a Strong Case Study: Tips for Winning a Case Competition

Babak Somekh,Yifan Zhang,Li-Chen Lim,Maria Elena (Maya) Baltazar Herrera Academy of Asian Business (AAB) 2017 Academy of Asian Business Review Vol.3 No.2

This paper presents personal experiences of faculty advisers in case writing, particularly to those who would like to participate in World Asian Case Competition. Four faculty advisers offered insightful guidelines and ideas to craft a high quality Asian business case study. First, this paper presented some emerging issues in case writing. Second, it discussed the challenges of Chinese business case writing. Third, a few tips are provided to help readers to write a case and to win case competitions. Finally, it addressed one of the challenging topics on how to showcase responsible businesses focusing on emerging issues and implications for case writing.

Amylin as a Future Obesity Treatment

Babak Dehestani,Nicholas RS Stratford,Carel W. le Roux 대한비만학회 2021 The Korean journal of obesity Vol.30 No.4

Obesity is defined as abnormal or excessive fat accumulation that contributes to detrimental health impacts. One-third of the population suffers from obesity, and it is important to consider obesity as a chronic disease requiring chronic treatment. Amylin is co-secreted with insulin from β pancreatic cells upon nutrient delivery to the small intestine as a satiety signal, acts upon sub-cortical homeostatic and hedonic brain regions, slows gastric emptying, and suppresses post-prandial glucagon responses to meals. Therefore, new pharmacological amylin analogues can be used as potential anti-obesity medications in individuals who are overweight or obese. In this narrative review, we analyse the efficacy, potency, and safety of amylin analogues. The synthetic amylin analogue pramlintide is an approved treatment for diabetes mellitus which promotes better glycaemic control and small but significant weight loss. AM833 (cagrilintide), an investigational novel long-acting acylated amylin analogue, acts as a non-selective amylin receptor. This calcitonin G protein-coupled receptor agonist can serve as an attractive novel treatment for obesity, resulting in reduction of food intake and significant weight loss in a dose-dependent manner.

Optimization of structural and mechanical engineering problems using the enriched ViS-BLAST method

Babak Dizangian,Mohammad Reza Ghasemi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.5

In this paper, an enhanced Violation-based Sensitivity analysis and Border-Line Adaptive Sliding Technique (ViS-BLAST) will be utilized for optimization of some well-known structural and mechanical engineering problems. ViS-BLAST has already been introduced by the authors for solving truss optimization problems. For those problems, this method showed a satisfactory enactment both in speed and efficiency. The Enriched ViS-BLAST or EVB is introduced to be vastly applicable to any solvable constrained optimization problem without any specific initialization. It uses one-directional step-wise searching technique and mostly limits exploration to the vicinity of FNF border and does not explore the entire design space. It first enters the feasible region very quickly and keeps the feasibility of solutions. For doing this important, EVB groups variables for specifying the desired searching directions in order to moving toward best solutions out or inside feasible domains. EVB was employed for solving seven numerical engineering design problems. Results show that for problems with tiny or even complex feasible regions with a larger number of highly non-linear constraints, EVB has a better performance compared to some records in the literature. This dominance was evaluated in terms of the feasibility of solutions, the quality of optimum objective values found and the total number of function evaluations performed.