Inverted Polymer Solar Cells with Sol-Gel Derived Cesium-Doped Zinc Oxide Thin Film as a Buffer Layer

Mehdi Ahmadi,Kavoos Mirabbaszadeh,Saeid Salari,Hamed Fatehy 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.5

An inverted structure of polymer solar cells based on Poly(3-hexylthiophene)(P3HT):[6-6] Phenyl-(6) butyric acid methyl ester (PCBM) with thin films of sol-gel derived Cesium doped ZnO (Cs:ZnO) was developed as an efficient cathode buffer layer. Doped and undoped thin films were deposited using a less studied method, doctor blade, which was compatible with Roll-2-Roll printing method. By comparing the effect of Cs:ZnO thin films with various dopant ratio on the performance of inverted polymer solar cells, 0.5% Cs doped ZnO was found as the most effective doping level among the selected doping ratios. Using 30 nm thickness of 0.5% Csn:ZnO thin film as an electron transport layer led to the average efficiency which was significantly higher than (9%) that of similar devices employing the same thickness of undoped ZnO film. Results showed that the devices fabricated with 1% and 2% cesium doped ZnO yielded lower power conversion efficiency, which could be due to the lower FF. Also, the influence of dopant incorporation on the optical transmittance and electrical conductivity of ZnO films was investigated.

Density-Controlled ZnO Nanorod Arrays in Polymer Solar Cells Based on Poly(3-hexylthiophene) and Indene-C60 Bis-Adduct

Mehdi Ahmadi,Kavoos Mirabbaszadeh,Mostafa Ketabchi 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.6

We investigated the effect of employing ZnO nanorods in an inverted polymer solar cell based on Poly(3-hexylthiophene) and Indene-C60 Bis-Adduct. Hydrothermal method was chosen to growth of vertically aligned ZnO nanorods on 30 nm thick ZnO seed layer. The samples were analyzed by x-ray diffraction (XRD),scanning electron microscopy (SEM), and electrical conductivity measurements. Indene-C60 Bis-Adduct, as new acceptor with higher-lying LUMO energy level than PCBM blended with P3HT. Efficient infiltration of polymer into interspaces between nanorod arrays concluded to improved performance of the device. Photovoltaic characteristic of inverted polymer solar cell with ZnO nanorods were compared with devices employed ZnO thin film. Inverted polymer solar cell based on Poly (3-hexylthiophene) and Indene-C60 Bis-Adduct hybridized with ZnO nanorods exhibited power conversion efficiency of 4.04% that was better than a device with ZnO thin film interlayer (3.80%).

UV-LEDs assisted peroxymonosulfate/Fe2+ for oxidative removal of carmoisine: The effect of chloride ion

Mehdi Ahmadi,Farshid Ghanbari,Alberto Alvarez,Susana Silva Martinez 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.8

The performance of UVA-LEDs assisted peroxymonosulfate (PMS)/Fe2+ system was evaluated on carmoisine (E122) decolorization. Complete color removal was obtained under the conditions of pH=3.0, PMS=1.5mM, Fe2+=1mM and 25 min reaction time. UVA-LEDs were preferable compared to conventional UVA lamp in terms of decolorization. The functions of Co2+, Cu2+, Mn2+ and Fe2+ were compared and their results showed that Co2+ and Fe2+ had the highest efficiencies. Moreover, the presence of chloride ion showed a double role in different concentrations in which promotional effect was observed in 100mM Cl−<, while inhibitory effect occurred in 1-10mM Cl−. However, the high concentration of chloride had no influence on mineralization of E122. The scavenging results demonstrated that the UV irradiation increased the contribution of HO•. In addition, in the presence of chloride ion, HOCl along with sulfate and hydroxyl radicals were the major oxidative agents.

Seismic Fragility Assessment of SMRFs with Drilled Flange Connections using Ground Motion Variability

Mehdi Maleki,Roohollah Ahmady Jazany,Mohammad Soheil Ghobadi 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4

Seismic behavior of Steel Moment Resisting Frames (SMRFs) with Drilled Flange (DF) connections as well as Reduced Beam Section (RBS) and Welded Unreinforced Flange-Bolted web (WUF-B) as a Pre-Northridge connection have been compared analytically considering Far-field earthquake-induced. The backbone curves of RBS and WUF connections are extracted from available studies and the backbone curve of DF connection is presented in this study in order to simulating the buildings models. DF, RBS, WUF connections and Panel Zone (PZ) are numerically modeled based on the proposed models provided by the prior researches and these models are applied to analyze low- and high-rise buildings designed in accordance with the relevant standards. Incremental Dynamic Analysis (IDA) process is utilized to evaluate the effects of DF connection on structural seismic response of SMRFs. Afterwards, the structures’ performance in different response levels is probabilistically assessed by means of IDA and fragility curves. The results show that the seismic demand of SMRFs with DF and RBS connections are so similar, specifically for low-rise buildings. Likewise, SMRFs with DF connection provide up to 43% higher seismic demand in high-rise buildings compared to RBS connection. Eventually, DF connection can be used as an authentic option in SMRFs.

A Descriptive Study of Occupational Health Services in Self-employed Enterprises (Nanoscale Enterprises), Shiraz, Iran

Mehdi Jahangiri,Akbar Rostamabadi,Parvaneh Yekzamani,Bahare Mahmood Abadi,Fariborz Behbood,Seyyedeh Fatemeh Ahmadi,Zahra Momeni 한국산업안전보건공단 산업안전보건연구원 2016 Safety and health at work Vol.7 No.4

Background: This study was conducted with aim of providing an overview of the current status of occupational health services and identifying the most common harmful agents at workplaces of Iranian self-employed enterprises (Nano-Scale Enterprises). Methods: A cross-sectional study was performed among a random sample including 1,758 employees engaging in self-employed enterprises with 5 and less employees. Results: Coverage of occupational health surveillance was very poor, annual health examinations were been conducted only for 64 (3.64%) of males and 31 (1.76%) of females, and occupational health trainings were not included of the services at all. Personal Protective Equipment were available in 462 (26.3%) of the enterprises. only in 0.4% of the enterprises working processes were been equipped by a local exhaust ventilation system. Difficult postures were the most common (81.5%) adverse working conditions. Conclusion: This study revealed a poor level of the implementation of occupational health services in Iranian self-employed enterprises. Based on the findings, providing basic training on the occupational health, more enforcing in conduction of health examinations and providing PPE, and taking appropriate strategies aimed at eliminating or minimizing work environment harmful agents are the major factor that should be considered to improve the level of occupational health services among the studied enterprises.

Production of Ultrafine-Grained Titanium with Suitable Properties for Dental Implant Applications by RS-ECAP Process

Mehdi Abbasi,Farshid Ahmadi,Mahmoud Farzin 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4

The only problem of pure titanium for dental implant applications is its low strength and failure under different loadings. Various studies have shown that the utilization of severe plastic deformation processes such as Equal Channel AngularPressing (ECAP), through reducing the grain size of titanium, can improve not only its mechanical properties but also itscorrosion resistance and biocompatibility. In this study, a reduced-scale ECAP process on pure titanium was performed toinvestigate the effects of scale reduction. An ECAP die was made with an internal diameter of d = 3 mm, and the tests wereperformed at 250 °C for several number of passes. It was found out that after 10 passes of reduced-scale ECAP, the grainsize of CP Ti had strongly been reduced from 25 to 122 nm. This sharp reduction in grain size resulted in an increase inmicro-hardness from 205.5 to 321.3 Hv. Moreover, Nano-hardness test results showed that after 10 passes, the hardness oftitanium increased from 2461 to 3812 MPa, and simultaneously elastic modulus decreased from 108.1 to 94.8 GPa. Suchreduction of elastic modulus of titanium for dental implant applications decreased stress-shielding and jaw bone damages. According to the results of this research, after RS-ECAP process the strength of titanium is greatly increased and its elasticmodulus is reduced, which are desirable features for dental implant applications. Since dental implants are small in size, thereduced ECAP process (d = 3–5 mm) can produce titanium implants with improved properties.

Seismic Behavior of Steel Braced Frames Equipped with Metal Foam

Mehdi Ebadi Jamkhaneh,Mohammadreza Rezaei,Masoud Ahmadi 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4

One of the methods for improving the seismic behavior of structures was to use inactive control devices. Recently, in civil engineering applications, a relatively new material named metal foam has been utilized progressively due to its high energy dissipation capability and remarkable axial strain. In this study, several non-linear time-history analyses were conducted for investigating the seismic behavior of steel frames equipped with the composite brace using a three-dimensional (3D) fi nite element (FE) method. Crushable foam (CF) and elastic-perfectly plastic models were considered for metal foam and steel members. FE results revealed that the maximum drift ratio decreased by 35% and 72% under near-fi eld and far-fi eld records in the steel frames equipped with composite brace compared to the conventional steel brace frames. Employing the composite brace led to prevent global buckling of the brace and consequently decrease in load-bearing capacity. Furthermore, composite brace caused the reduction of bending moment demand in the fi rst-story column by 18%.

An Iterative Approach to Determine the Complexity of Local Models for Robust Identification of Nonlinear Systems

Salman Ahmadi,Mehdi Karrari 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.1

In this paper, a new multi-model approach is proposed for identification of nonlinear systems. In similar identification methods, the operating space is partitioned and a local model is suggested for each partition. In such approaches, since the same linear structure is often used for all local models; huge number of local linear models is usually required to reasonably model an operating region with severely nonlinear dynamics. Therefore the size of the global model may exponentially increase; and as a result model robustness may decrease. In the proposed approach the best model structure is selected for the particular nonlinear study system in an iterative approach. At each iteration, a choice is made to increase number of local models and/or increase the local model complexity. Furthermore, it determines the complexity of local models based on increasing the model accuracy and ensuring the model robustness. In order to optimize the model approximation capability and model robustness, a model term selection approach based on a forward orthogonal least squares algorithm and a criterion that minimizes the sum of the variance of the parameter estimates is applied. Simulation results show that the proposed method results in an excellent validation performance with fewer parameters.

Chitosan Scaffold Containing Periostin Enhances Sternum Bone Healing and Decreases Serum Level of TNF-α and IL-6 after Sternotomy in Rat

Salehiamin Mehdi,Toolee Heidar,Azami Mahmoud,Tafti Seyed Hossein Ahmadi,Mojaverrostami Sina,Halimi Shahnaz,Barakzai Shogoofa,Sobhani Aligholi,Abbasi Yasaman 한국조직공학과 재생의학회 2022 조직공학과 재생의학 Vol.19 No.4

BACKGROUND: In the aftermath of bone injuries, such as cranium and sternum, bone wax (BW) is used to control bleeding from the bone surfaces during surgery. Made up of artificial substances, however, it is associated with many complications such as inflammation, increased risk for infection, and bone repair delay. We, therefore, in this study set out to design and evaluate a novel BW without the above-mentioned side-effects reported for other therapies. METHODS: The pastes (new BW(s)) were prepared in the laboratory and examined by MTT, MIC, MBC, and degradability tests. Then, 60 adult male Wistar rats, divided into six equal groups including chitosan (CT), CT-octacalcium phosphate (OCP), CT-periostin (Post), CT-OCP-Post, Control (Ctrl), and BW, underwent sternotomy surgery. Once the surgeries were completed, the bone repair was assessed radiologically and thereafter clinically in vivo and in vitro using CT-scan, H&E, ELISA, and qRT-PCR. RESULTS: All pastes displayed antibacterial properties and the CT-Post group had the highest cell viability compared to the control group. In contrast to the BW, CT-Post group demonstrated weight changes in the degradability test. In the CT-Post group, more number of osteocyte cells, high trabeculae percentage, and the least fibrous connective tissue were observed compared to other groups. Additionally, in comparison to the CT and Ctrl groups, higher alkaline phosphatase activity, as well as decreased level of serumtumor necrosis factor-a, interleukin-6, andOCNin the CT-Post group was evident. Finally, Runx2, OPG, and RANKL genes’ expression was significantly higher in the CT-Post group than in other groups. CONCLUSION: Our results provide insights into the desirability of pastes in terms of cellular viability, degradability, antibacterial properties, and surgical site restoration compared to the BW group. Besides, Periostin could enhance the osteogenic properties of bone tissue defect site.

A Descriptive Study of Occupational Health Services in Self-employed Enterprises (Nanoscale Enterprises), Shiraz, Iran

Jahangiri, Mehdi,Rostamabadi, Akbar,Yekzamani, Parvaneh,Abadi, Bahare Mahmood,Behbood, Fariborz,Ahmadi, Seyyedeh Fatemeh,Momeni, Zahra Occupational Safety and Health Research Institute 2016 Safety and health at work Vol.7 No.4

Background: This study was conducted with aim of providing an overview of the current status of occupational health services and identifying the most common harmful agents at workplaces of Iranian self-employed enterprises (Nano-Scale Enterprises). Methods: A cross-sectional study was performed among a random sample including 1,758 employees engaging in self-employed enterprises with 5 and less employees. Results: Coverage of occupational health surveillance was very poor, annual health examinations were been conducted only for 64 (3.64%) of males and 31 (1.76%) of females, and occupational health trainings were not included of the services at all. Personal Protective Equipment were available in 462 (26.3%) of the enterprises. only in 0.4% of the enterprises working processes were been equipped by a local exhaust ventilation system. Difficult postures were the most common (81.5%) adverse working conditions. Conclusion: This study revealed a poor level of the implementation of occupational health services in Iranian self-employed enterprises. Based on the findings, providing basic training on the occupational health, more enforcing in conduction of health examinations and providing PPE, and taking appropriate strategies aimed at eliminating or minimizing work environment harmful agents are the major factor that should be considered to improve the level of occupational health services among the studied enterprises.