Experimental verification for simulation study of Pt/CNT nanostructured cathode catalyst layer for PEM fuel cells

In this study, parametric study on the cathode catalyst layer in a Proton Exchange Membrane (PEM) fuel cell was conducted. Steady-state, two dimensional (2D) and nonisothermal conditions were proposed as critical hypotheses of work in essence. Multi-component mass diffusion along with convection mechanism in a single cell, conduction changes of proton and electron with experimental data and Knudsen diffusion which has a crucial impact on the simulation task in nanoscale, were considered in our study. Moreover, carbon nanotube (CNT), platinum (Pt) and Nafion loading effects as well as the porosity characteristics in a single-phase flow at different catalyst layer (CL) thicknesses were thoroughly investigated. The results presented herein, revealed that the amount of Pt and CNT has more profound effect than catalyst porosity. Based on the results derived, the model presented could be a promising mean to develop and construct a nanostructured catalyst layer. Meanwhile, our modified agglomerate model predicts the performance of fuel cell systems in different experimental conditions.     

A proposed structural design method considering fluid viscous damper degradations

The purpose of this study is to perform a seismic assessment of the moment resistant steel structures enhanced with viscous dampers where the dampers are degraded due to possible leak of viscous fluid. This paper proposes a design procedure based on corrected response spectrums as a result of seismic assessments based on nonlinear time series analyses on three‐, five‐, and seven‐story steel frame structures denoted as “generic structures.” The proposed design procedure is a seismic displacement‐based design methodology for buildings with viscous dampers as passive energy dissipation systems. Prior literature on these types of structures often overlook the viscous dampers degradation due to the fluid leak. In this paper, in order to study these effects, a target displacement is specified at first and the lateral forces and required stiffness are obtained. The effectiveness of the proposed procedure is verified with the collapse fragility curves of the generic structures according to the ASCE 7‐10 and displacement‐based design methodology. The results show that the structures designed based on proposed procedure demonstrate acceptable performance with degrading dampers.     

Ambulatory system for human motion analysis using a kinematic sensor: monitoring of daily physical activity in the elderly

A new method of physical activity monitoring is presented, which is able to detect body postures (sitting, standing, and lying) and periods of walking in elderly persons using only one kinematic sensor attached to the chest. The wavelet transform, in conjunction with a simple kinematics model, was used to detect different postural transitions (PTs) and walking periods during daily physical activity. To evaluate the system, three studies were performed. The method was first tested on 11 community-dwelling elderly subjects in a gait laboratory where an optical motion system (Vicon) was used as a reference system. In the second study, the system was tested for classifying PTs (i.e., lying-to-sitting, sitting-to-lying, and turning the body in bed) in 24 hospitalized elderly persons. Finally, in a third study monitoring was performed on nine elderly persons for 45-60 min during their daily physical activity. Moreover, the possibility-to-perform long-term monitoring over 12 h has been shown. The first study revealed a close concordance between the ambulatory and reference systems. Overall, subjects performed 349 PTs during this study. Compared with the reference system, the ambulatory system had an overall sensitivity of 99% for detection of the different PTs. Sensitivities and specificities were 93% and 82% in sit-to-stand, and 82% and 94% in stand-to-sit, respectively. In both first and second studies, the ambulatory system also showed a very high accuracy (> 99%) in identifying the 62 transfers or rolling out of bed, as well as 144 different posture changes to the back, ventral, right and left sides. Relatively high sensitivity (> 90%) was obtained for the classification of usual physical activities in the third study in comparison with visual observation. Sensitivities and specificities were, respectively, 90.2% and 93.4% in sitting, 92.2% and 92.1% in "standing + walking," and, finally, 98.4% and 99.7% in lying. Overall detection errors (as percent of range) were 3.9% for "standing + walking," 4.1% for sitting, and 0.3% for lying. Finally, overall symmetric mean average errors were 12% for "standing + walking," 8.2% for sitting, and 1.3% for lying.     

Peer acceptance, self-perceptions, and social skills of learning disabled students prior to identification.

This study addressed how learning disabled students prior to identification (LDPI), low-achieving (LA), average-achieving (AA), and high-achieving (HA) students compare on peer, teacher, and self assessments of social status and social skills in the fall and spring of kindergarten. Two hundred thirty-nine Black, Hispanic, and White students, 78% of a kindergarten population, participated. Controlling for age, sex, and achievement levels, four groups were identified: LDPI, LA, AA, and HA. In fall and spring of kindergarten all students were administered measures of peers' perceptions of social status, teacher's assessment of behavior problems and social skills, and self-perception. MANOVA and a stepwise discriminant function analysis revealed that as early as 8 weeks after entering kindergarten, LDPI students differed significantly from their peers on social variables and attention problems. Results suggest that later social difficulties of LD students are not solely a function of a history of low achievement and low teacher acceptance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-concept and peer acceptance in students with learning disabilities: A four- to five-year prospective study.

Examined the peer relations and self-concepts of students prior to and following their identification by the school district as learning disabled (LD) in a 4- to 5-yr prospective study. Self-concept ratings (kindergarten–4th grade) and peer acceptance ratings (kindergarten–3rd grade), as well as academic achievement scores, were compared across 3 groups: LD students who were placed in resource special education programs during 2nd grade, low-achieving (LA) students, and average-achieving/high-achieving (AA/HA) students. For peer acceptance, AA/HA students' scores were higher than LA students' scores only. No between-groups differences were obtained during any school year on the self-concept measure. Findings suggest that LD students' self-perceptions are not negatively affected by academic and social difficulties in the early grades or by the identification and labeling process. Though generalization is limited by the small sample size, few studies have examined students with learning disabilities longitudinally or prior to and following their identification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A new approach for design of an efficient FPGA-based reconfigurable convolver for image processing

The Journal of Supercomputing - Two-dimensional convolution plays a fundamental role in different image processing applications. Image convolving with different kernel sizes enriches the overall...     

A hybrid reciprocal model of PCA and K-means with an innovative approach of considering sub-datasets for the improvement of K-means initialization and step-by-step labeling to create clusters with high interpretability

Pattern Analysis and Applications - The K-means algorithm is a popular clustering method, which is sensitive to the initialization of samples and selecting the number of clusters. Its performance...     

Fracture analysis on flexible roll forming process of anisotropic Al6061 using ductile fracture criteria and FLD

In this research, the fracture phenomenon was investigated on flexible roll forming process of channel section using ductile fracture criteria and forming limit diagram (FLD) by considering the effect of anisotropy. For this purpose, a finite element simulation of the process using the ABAQUS software was done. The fracture in this process was evaluated by considering six types of ductile fracture criteria by UMAT subroutine implementation on the FEM software and using FLD criterion. Experimental tests were performed on 27 blanks of Al6061-T6 using flexible roll forming machine made in Shahid Rajaee Teacher Training University (SRTTU). Numerical results were validated by experimental results. In addition, prediction of occurrence and fracture position by ductile fracture criteria and FLD criterion were compared with experimental results; the Argon criterion was chosen as the most appropriate criterion to predict the fracture position and its occurrence. The fracture occurrence was only observed in a 60° bending angle for 1.5- and 2-mm thicknesses, and the fracture position error percentages of the Argon criterion with experiments for these cases were 18.7 and 3.5%, respectively. Also, the effects of parameters such as sheet thickness, bending radius, and bending angle on the fracture phenomenon by using the selected criterion of Argon were studied.     

Low-temperature Magnesiothermic Synthesis of Mesoporous Silicon Carbide from an MCM-48/Polyacrylamide Nanocomposite Precursor

Mesoporous silicon carbide with high specific surface area was successfully synthesized from an MCM-48/ polyacrylamide nanocomposite precursor in the temperature range of 550—600℃（below the melting point of Mg） by means of a magnesiothermic reduction process.The MCM-48/polyacrylamide precursor nanocomposite was prepared by in-situ polymerization of acrylamide monomer in the presence of mesoporous MCM-48 synthesized by sol-gel method.The physicochemical properties and microstructures of the nanocomposite precursor and the low-temperature SiC product were characterized by X-ray diffraction（XRD）, differential scanning calorimetry-thermo gravimetric analysis（DSC-TGA）,transmission electron microscopy （TEM） and N₂ adsorption—desorption.TEM micrographs and Brunauer—Emmett—Teller（BET） gas adsorption studies showed that the SiC powder was nanocrystalline and had a specific surface area of 330 m²/g and a mesoporosity in the range of 2—10 nm.The presence of an exothermic peak in the DSC trace corresponds to the self-combustion process of the SiC magnesiothermic synthesis.The results also show that the carbon in excess to that required to produce SiC plays a role in the reduction of the SiO₂.The mechanism of magnesiothermic synthesis of mesoporous SiC is discussed.     

Synthesis,characterization and catalytic activity studies of Pd-based supported nanoparticle catalyst anchoring on poly(N-vinyl-2-pyrrolidone) modified CMK-3

Pd nanoparticle-poly(N-vinyl-2-pyrrolidone)/CMK-3 (Pd-PVP/CMK-3) composite was prepared by in situ polymerization method which was effectively employed as a novel heterogeneous catalyst for the Suzuki–Miyaura cross-coupling reaction. The physical and chemical properties of Pd nanoparticle-PVP/CMK-3 were investigated using FT-IR, XRD, BET, UV–vis, TEM and TGA techniques. The reaction was carried out between aryl halides and phenylboronic acid in the presence of water at room temperature. The stability of the catalyst was good and could be reused 10 times without much loss of activity in Suzuki–Miyaura reaction.