Crack detection in rectangular plate by electromechanical impedance method: modeling and experiment

Mehdi Rajabi,Mahnaz Shamshirsaz,Mahyar Naraghi 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.4

Electromechanical impedance method as an efficient tool in Structural Health Monitoring (SHM) utilizes the electromechanical impedance of piezoelectric materials which is directly related to the mechanical impedance of the host structure and will be affected by damages. In this paper, electromechanical impedance of piezoelectric patches attached to simply support rectangular plate is determined theoretically and experimentally in order to detect damage. A pairs of piezoelectric wafer active sensor (PWAS) patches are used on top and bottom of an aluminum plate to generate pure bending. The analytical model and experiments are carried out both for undamaged and damaged plates. To validate theoretical models, the electromechanical impedances of PWAS for undamaged and damaged plate using theoretical models are compared with those obtained experimentally. Both theoretical and experimental results demonstrate that by crack generation and intensifying this crack, natural frequency of structure decreases. Finally, in order to evaluate damage severity, damage metrics such as Root Mean Square Deviation (RMSD), Mean Absolute Percentage Deviation (MAPD), and Correlation Coefficient Deviation (CCD) are used based on experimental results. The results show that generation of crack and crack depth increasing can be detectable by CCD.

Ischiorectal Block with Bupivacaine for Post Hemorrhoidectomy Pain

Rajabi, Mehdi,Hosseinpour, Mehrdad,Jalalvand, Faranak,Afshar, Mohammad,Moosavi, Golamabbas,Behdad, Samin The Korean Pain Society 2012 The Korean Journal of Pain Vol.25 No.2

Background: Hemorrhoid is one of the most common surgical diseases occurring in the anorectal region. In this study, we evaluated the effect of ischiorectal fossa block on alleviating post hemorrhoidectomy pain. Methods: In this study, 90 patients suffering from hemorrhoids were evaluated. They were randomly divided into 3 groups. The first group had no block, the second group an ischiorectal block with placebo (normal saline), and the third group a preemptive ischiorectal block with bupivacaine. Postoperative variables such as pain intensity, pethidine consumption, nausea, and vomiting were compared between the groups. Results: The postoperative pain score in group 1 was $8.5{\pm}1.3$ and $8.1{\pm}0.9$ (P=NS) in group 2. The post operative analgesic demand was $3.1{\pm}1.5$ and $3.3{\pm}1.8$ hours in groups 1 and 2, respectively (P=NS). The post operative pain score and analgesic demand were $4.2{\pm}2.1$ and $9.3{\pm}2.7$ hours, respectively, in group 3 (P < 0.0001). Conclusions: Preemptive ischiorectal block reduces the posthemorrhoidectomy pain and opioid demand.

Original Articles : Ischiorectal Block with Bupivacaine for Post Hemorrhoidectomy Pain

( Mehdi Rajabi ),( Mehrdad Hosseinpour ),( Faranak Jalalvand ),( Mohammad Afshar ),( Golamabbas Moosavi ),( Samin Behdad ) 대한통증학회 2012 The Korean Journal of Pain Vol.25 No.2

Background: Hemorrhoid is one of the most common surgical diseases occurring in the anorectal region. In this study, we evaluated the effect of ischiorectal fossa block on alleviating post hemorrhoidectomy pain. Methods: In this study, 90 patients suffering from hemorrhoids were evaluated. They were randomly divided into 3 groups. The first group had no block, the second group and ischiorectal block with placebo (normal saline), and the third group a preemptive ischiorectal block with bupivacaine. Postoperative variables such as pain intensity, pethidine consumption, nausea, and vomiting were compared between the groups. Results: The postoperative pain score in group 1 was 8.5±1.3 and 8.1±0.9 (P=NS) in group 2. The post operative analgesic demand was 3.1±1.5 and 3.3±1.8 hours in groups 1 and 2, respectively (P=NS). The post operative pain score and analgesic demand were 4.2±2.1 and 9.3±2.7 hours, respectively, in group 3 (P<0.0001). Conclusions: Preemptive ischiorectal block reduces the posthemorrhoidectomy pain and opioid demand. (Korean J Pain 2012; 25: 89-93)

Bending analysis of a micro sandwich skew plate using extended Kantorovich method based on Eshelby-Mori-Tanaka approach

Javad Rajabi,Mehdi Mohammadimehr 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.5

In this research, bending analysis of a micro sandwich skew plate with isotropic core and piezoelectric composite face sheets reinforced by carbon nanotube on the elastic foundations are studied. The classical plate theory (CPT) are used to model micro sandwich skew plate and to apply size dependent effects based on modified strain gradient theory. Eshelby-Mori-Tanaka approach is considered for the effective mechanical properties of the nanocomposite face sheets. The governing equations of equilibrium are derived using minimum principle of total potential energy and then solved by extended Kantorovich method (EKM). The effects of width to thickness ratio and length to width of the sandwich plate, core-to-face sheet thickness ratio, the material length scale parameters, volume fraction of CNT, the angle of skew plate, different boundary conditions and types of cores on the deflection of micro sandwich skew plate are investigated. One of the most important results is the reduction of the deflection by increasing the angle of the micro sandwich skew plate and decreasing the deflection by decreasing the thickness of the structural core. The results of this research can be used in modern construction in the form of reinforced slabs or stiffened plates and also used in construction of bridges, the wing of airplane.

Hydro-thermo-mechanical biaxial buckling analysis of sandwich micro-plate with isotropic/orthotropic cores and piezoelectric/polymeric nanocomposite face sheets based on FSDT on elastic foundations

Javad Rajabi,Mehdi Mohammadimehr 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.4

In the present work, the buckling analysis of micro sandwich plate with an isotropic/orthotropic cores and piezoelectric/polymeric nanocomposite face sheets is studied. In this research, two cases for core of micro sandwich plate is considered that involve five isotropic Devineycell materials (H30, H45, H60, H100 and H200) and an orthotropic material also two cases for facesheets of micro sandwich plate is illustrated that include piezoelectric layers reinforced by carbon and boron-nitride nanotubes and polymeric matrix reinforced by carbon nanotubes under temperature-dependent and hydro material properties on the elastic foundations. The first order shear deformation theory (FSDT) is adopted to model micro sandwich plate and to apply size dependent effects from modified strain gradient theory. The governing equations are derived using the minimum total potential energy principle and then solved by analytical method. Also, the effects of different parameters such as size dependent, side ratio, volume fraction, various material properties for cores and facesheets and temperature and humidity changes on the dimensionless critical buckling load are investigated. It is shown from the results that the dimensionless critical buckling load for boron nitride nanotube is lower than that of for carbon nanotube. It is illustrated that the dimensionless critical buckling load for Devineycell H200 is highest and lowest for H30. Also, the obtained results for micro sandwich plate with piezoelectric facesheets reinforced by carbon nanotubes (case b) is higher than other states (cases a and c).The results of this research can be used in aircraft, automotive, shipbuilding industries and biomedicine.

The role of risk perception, risk communication, and demographic factors in COVID-19 preventive behaviors: an online survey in Iran

Mansour Rezaei,Nader Rajabi Gilan,Ali Almasi,Mehdi Khezeli,Fatemeh Jamshidi Nazar,Zahra Jorjoran Shushtari,Yahya Salimi,Farid Najafi,Neda Sarabi,Shahram Saeidi,Saeid Saeidi 질병관리본부 2022 Osong Public Health and Research Persptectives Vol.13 No.4

Objectives: This study investigated preventive behaviors toward coronavirus disease 2019 (COVID-19) and related factors in a Kurdish Iranian sample.Methods: This online survey was conducted among the population aged 18 and above in Kermanshah Province, in western Iran, in April 2020. Samples were invited and recruited through social media. Data were collected using a questionnaire consisting of 4 sections (questions on demographic variables, risk perception, risk communication, and COVID-19 preventive behaviors) and analyzed using Stata ver. 8.Results: The Pearson correlation test showed that risk communication was significantly correlated with COVID-19 preventive behaviors (r=0.320, p<0.01). In the final model, where the explanatory power increased with the entry of the risk communication variable, the variables explained a total of 14% of variance in COVID-19 preventive behaviors. Sex (β=−0.482), risk perception (β=0.047), and risk communication (β=0.662) were significant determinants.Conclusion: Risk communication and risk perception related to COVID-19, as well as being a woman, were determinants of COVID-19 preventive behaviors.

Synthesis of new phosphate derivative of benzothiazole and its inhibiting effect on two series of human neuroblastoma cell growth

Mahshid Nikpour Nezhati,Gholam Hossein Riazi,Homayon Ahmad Panahi,Elham Moniri,Nasir Ahmad Rajabi,Mohammad Mehdi Sadughi,Natasha Rahmani Zaker,Robab Ardekani,Reihaneh Kooshkestani 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.3

The sodium salt of di ((1-hydroxy-2-benzothiazolium-1-yl) ethyliden-1,1-H-bisphosphonic acid) orthophosphate was synthesized and its toxicity and viability effects screened on two different human neuroblastoma cell lines. This novel derivative of benzothiazole provides a new compound in connection with research and therapeutic application for tumor cell growth inhibition. Benzothiazole was alkylated in reaction with bromoacetic acid and then converted to its H-bisphosphonic acid derivative in presence of H3PO3/POCl3. The procedure led to formation of two molecules of corresponding H-bisphosphonic acid which attached together via a phosphate bridge. The investigated compound exhibits activities (IC50 value) ranging from 14-23 μM (corresponding to human neuroblastoma SK-BE (2)and SK-NM-C cells).