Effect of calcination and reaction conditions on the catalytic performance of Co–Ni/Al2O3 catalyst for CO hydrogenation

Akbar Zare,Mehdi Shiva,Ahad Zare,Ali Akbar Mirzaei 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.6

The Co–Ni/Al2O3 catalysts prepared using impregnation procedure, were used for the Fischer–Tropsch synthesis. The effect of calcination conditions of the catalyst as well as reactor situation was studied. It was found that the catalyst calcined at 550 8C for 6 h in air atmosphere has shown the best catalytic performance for CO hydrogenation. The best operational conditions were obtained as following:T = 350 8C, P = 1 atm and H2/CO = 2/1.

The Effect of Occupational Noise Exposure on Serum Cortisol Concentration of Night-shift Industrial Workers: A Field Study

Zare, Sajad,Baneshi, Mohammad R.,Hemmatjo, Rasoul,Ahmadi, Saeid,Omidvar, Mohsen,Dehaghi, Behzad F. Occupational Safety and Health Research Institute 2019 Safety and health at work Vol.10 No.1

Background: In both developed and developing countries, noise is regarded as the most common occupational hazard in various industries. The present study aimed to examine the effect of sound pressure level (SPL) on serum cortisol concentration in three different times during the night shift. Methods: This case-control study was conducted among 75 workers of an industrial and mining firm in 2017. The participants were assigned to one of the three groups (one control and two case groups), with an equal number of workers (25 participants) in each group. Following the ISO 9612 standard, dosimetry was adopted to evaluate equivalent SPL using a TES-1345 dosimeter. The influence of SPL on serum cortisol concentration was measured during the night shift. The serum cortisol concentration was measured using a radioimmunoassay (RIA) test in the laboratory. Repeated measure analysis of variance and linear mixed models were used with ${\alpha}=0.05$. Results: The results indicated a downward trend in the serum cortisol concentration of the three groups during the night shift. Both SPL and exposure time significantly affected cortisol concentration (p < 0.0001, p < 0.0001). Conversely, age and body mass index had no significant influence on cortisol concentration (p = 0.360, p = 0.62). Conclusion: Based on the obtained results, increasing SPL will lead to enhancement of serum cortisol concentration. Given that cortisol concentration varies while workers are exposed to different SPLs, this hormone can be used as a biomarker to study the effect of noise-induced stress.

Comparison between Parametric and Semi-parametric Cox Models in Modeling Transition Rates of a Multi-state Model: Application in Patients with Gastric Cancer Undergoing Surgery at the Iran Cancer Institute

Zare, Ali,Mahmoodi, Mahmood,Mohammad, Kazem,Zeraati, Hojjat,Hosseini, Mostafa,Naieni, Kourosh Holakouie Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.11

Background: Research on cancers with a high rate of mortality such as those occurring in the stomach requires using models which can provide a closer examination of disease processes and provide researchers with more accurate data. Various models have been designed based on this issue and the present study aimed at evaluating such models. Materials and Methods: Data from 330 patients with gastric cancer undergoing surgery at Iran Cancer Institute from 1995 to 1999 were analyzed. Cox-Snell Residuals and Akaike Information Criterion were used to compare parametric and semi-parametric Cox models in modeling transition rates among different states of a multi-state model. R 2.15.1 software was used for all data analyses. Results: Analysis of Cox-Snell Residuals and Akaike Information Criterion for all probable transitions among different states revealed that parametric models represented a better fitness. Log-logistic, Gompertz and Log-normal models were good choices for modeling transition rate for relapse hazard (state $1{\rightarrow}state$ 2), death hazard without a relapse (state $1{\rightarrow}state$ 3) and death hazard with a relapse (state $2{\rightarrow}state$ 3), respectively. Conclusions: Although the semi-parametric Cox model is often used by most cancer researchers in modeling transition rates of multistate models, parametric models in similar situations- as they do not need proportional hazards assumption and consider a specific statistical distribution for time to occurrence of next state in case this assumption is not made - are more credible alternatives.

Novel aspects of elastic flapping wing: Analytical solution for inertial forcing

Zare, Hadi,Pourtakdoust, Seid H.,Bighashdel, Ariyan Techno-Press 2018 Advances in aircraft and spacecraft science Vol.5 No.3

The structural dynamics (SD) behavior of Elastic Flapping Wings (EFWs) is investigated analytically as a novel approach in EFWs analysis. In this regard an analytical SD solution of EFW undergoing a prescribed rigid body motion is initially derived, where the governing equations are expressed in modal space. The inertial forces are also analytically computed utilizing the actuator induced acceleration effects on the wing structure, while due to importance of analytical solution the linearity assumption is also considered. The formulated initial-value problem is solved analytically to study the EFW structural responses, where the effect of structure-actuator frequency ratio, structure-flapping frequency ratio as well as the structure damping ratio on the EFW pick amplitude is analyzed. A case study is also simulated in which the wing is modeled as an elastic beam with shell elements undergoing a prescribed sinusoidal motion. The corresponding EFW transient and steady response in on-off servo behavior is investigated. This study provides a conceptual understanding for the overall EFW SD behavior in the presence of inertial forces plus the servo dynamics effects. In addition to the substantial analytical results, the study paves a new mathematical way to better understanding the complex role of SD in dynamic EFWs behavior. Specifically, similar mathematical formulations can be carried out to investigate the effect of aerodynamics and/or gravity.

Efficiency of stress transfer between polymer matrix and nanoplatelets in clay/polymer nanocomposites

Zare, Yasser,Fasihi, Mohammad,Rhee, Kyong Yop Elsevier 2017 Applied clay science Vol.143 No.-

<P><B>Abstract</B></P> <P>The Hui-Shia model, which considers the complete stress transfer between polymer matrix and particles (perfect interfacial adhesion), overpredicts the Young's modulus of clay/polymer nanocomposites (CPN). In this work, the effective aspect ratio and volume fraction of nanoclay are expressed assuming the imperfect load transfer, the minimum length of platelets required for efficient stress transfer (<I>L</I> <SUB> <I>c</I> </SUB>) and the interfacial shear strength (<I>τ</I>). Additionally, “<I>I</I>” parameter as the level of stress transfer in CPN is defined and determined using the effective parameters. The large nanoclay platelets with low “<I>L</I> <SUB> <I>c</I> </SUB>” give a high level of “<I>I</I>”. Also, high “<I>L</I> <SUB> <I>c</I> </SUB>” and slight “<I>τ</I>” observe the poor levels of effective parameters and Young's modulus of CPN. The “<I>I</I>” values are calculated for some samples which indicate the different levels of stress transfer in CPN. It is possible to analyze the levels of interfacial properties and stress transfer in CPN using the developed model.</P> <P><B>Highlight</B></P> <P> <UL> <LI> The Hui-Shia model is developed for Young's modulus of clay/polymer nanocomposites. </LI> <LI> The effective aspect ratio and volume fraction of nanoclay are expressed. </LI> <LI> The critical length of platelets and interfacial shear strength are assumed. </LI> <LI> “<I>I</I>” parameter is defined as the level of stress transfer and determined. </LI> </UL> </P>

A simple model for constant storage modulus of poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes nanocomposites at low frequencies assuming the properties of interphase regions and networks

Zare, Yasser,Rhim, Sungsoo,Garmabi, Hamid,Rhee, Kyong Yop Elsevier 2018 Journal of the mechanical behavior of biomedical m Vol.80 No.-

<P><B>Abstract</B></P> <P>The networks of nanoparticles in nanocomposites cause solid-like behavior demonstrating a constant storage modulus at low frequencies. This study examines the storage modulus of poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes (CNT) nanocomposites. The experimental data of the storage modulus in the plateau regions are obtained by a frequency sweep test. In addition, a simple model is developed to predict the constant storage modulus assuming the properties of the interphase regions and the CNT networks. The model calculations are compared with the experimental results, and the parametric analyses are applied to validate the predictability of the developed model. The calculations properly agree with the experimental data at all polymer and CNT concentrations. Moreover, all parameters acceptably modulate the constant storage modulus. The percentage of the networked CNT, the modulus of networks, and the thickness and modulus of the interphase regions directly govern the storage modulus of nanocomposites. The outputs reveal the important roles of the interphase properties in the storage modulus.</P>

Roles of filler dimensions, interphase thickness, waviness, network fraction, and tunneling distance in tunneling conductivity of polymer CNT nanocomposites

Zare, Yasser,Garmabi, Hamid,Rhee, Kyong Yop Elsevier 2018 Materials chemistry and physics Vol.206 No.-

<P><B>Abstract</B></P> <P>We present a simple model to express the tunneling conductivity of polymer CNT nanocomposites as a function of the filler dimensions, filler conductivity, interphase thickness, waviness, fraction of networked CNTs, and tunneling distance. This model expresses the percolation threshold and the fraction of networked CNTs in terms of filler dimensions, waviness, and interphase thickness. The model was tested using experimental results from the literature. The predictions show good agreement with the experimental results in all samples, demonstrating the model's robustness for estimating tunneling conductivity. Moreover, the tunneling distance decreases as the filler concentration increases in all samples. The model parameters have a reasonable effect on the tunneling conductivity. The waviness and tunneling distance inversely affect the tunneling conductivity. Further, the waviness weakens the effective length of the nanotubes, and large tunneling distances cannot effectively transfer electrons between two adjacent nanotubes. The interphase thickness directly controls the tunneling conductivity, because a thick interphase reduces the percolation threshold. Poor percolation also creates large and dense conductive networks in nanocomposites, which is desirable for conductivity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simple model for tunneling conductivity of polymer-CNT nanocomposites is suggested. </LI> <LI> Interphase thickness, fraction of networked CNTs, and tunneling distance are assumed. </LI> <LI> The model expresses the percolation threshold and the fraction of networked CNTs. </LI> <LI> The model is tested using experimental results from the literature and parametric analyses. </LI> <LI> The predictions show good agreement with the experimental results in all samples. </LI> </UL> </P>

A two-step technique for tensile strength of montmorillonite/polymer nanocomposites assuming filler morphology and interphase properties

Zare, Yasser,Rhee, Kyong Yop Elsevier 2017 Applied clay science Vol.150 No.-

<P><B>Abstract</B></P> <P>This paper presents a two-step methodology for prediction of tensile strength in montmorillonite/polymer nanocomposites (MPN) assuming the effects of montmorillonite morphology (intercalation/exfoliation) and interphase properties. The suggested technique is evaluated by the experimental data of tensile strength in some samples. A good agreement is shown between experimental measurements and predictions, which can determine the intercalation/exfoliation level and interphase properties. A high aspect ratio of Mt platelets increases the interfacial interaction and mechanical involvement between polymer chains and nanoparticles causing high strengthening effect. Moreover, high concentration of well-exfoliated Mt as well as thick and strong interphase produces desirable tensile strength in MPN.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A two-step methodology for tensile strength of Mt/polymer nanocomposites is presented. </LI> <LI> The Mt morphology and interphase properties are assumed by a simple model. </LI> <LI> The suggested methodology shows good agreement with the experimental data. </LI> <LI> The high concentration of well-exfoliated platelets causes a high strength. </LI> <LI> The tensile stregth of MPN directly relates to the thickness and strength of interphase. </LI> </UL> </P>

Simplification and development of McLachlan model for electrical conductivity of polymer carbon nanotubes nanocomposites assuming the networking of interphase regions

Zare, Yasser,Rhee, Kyong Yop Elsevier 2019 Composites Part B, Engineering Vol.156 No.-

<P><B>Abstract</B></P> <P>This paper simplifies and develops the conventional model suggested by McLachlan for electrical conductivity of polymer CNT nanocomposites. The original model expresses the conductivity as a function of filler concentration, filler conductivity, filler percolation threshold and an exponent. However, this model is developed by considering the roles of interfacial tension between polymer matrix and nanoparticles, tunneling distance between adjacent nanotubes, interphase regions around nanoparticles and waviness of CNT. The experimental results of conductivity for some samples and the analysis of the effects of various parameters on the conductivity evaluate the developed model. The predictions demonstrate fine agreement with the experimental results and the parameters show acceptable roles in the conductivity of nanocomposites. A large tunneling distance significantly decreases the conductivity to zero. Likewise, the higher and slighter surface energies of the polymer matrix and filler, respectively cause an improved conductivity. A thin interphase produces very low conductivity, while a thick interphase and a low waviness improve the conductivity.</P>

Expansion of Kolarik model for tensile strength of polymer particulate nanocomposites as a function of matrix, nanoparticles and interphase properties

Zare, Yasser,Rhee, Kyong Yop Academic Press 2017 Journal of Colloid and Interface Science Vol. No.

<P><B>Abstract</B></P> <P>Kolarik proposed a model for tensile strength of polymer particulate composites based on the cubic orthogonal skeleton or three perpendicular plates (3PP) system. In this paper, Kolarik model is expanded for tensile strength of polymer nanocomposites containing spherical nanoparticles assuming the interphase properties. This model expresses the strength as a function of interphase properties. This development is performed using some models such as Pukanszky and Nicolais-Narkis. The expanded model is applied to calculate the thickness and strength of interphase by the experimental results. Furthermore, the strength of polymer nanocomposites is evaluated at different levels of material and interphase properties. The experimental data show good agreement with the predictions of the developed model.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>