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21.
Julio C. Albornoz David A. Landínez Téllez Jairo Roa-Rojas Julian A. Munévar Elisa Baggio-Saitovich 《Journal of Superconductivity and Novel Magnetism》2013,26(6):2313-2317
In this work, we report synthesis and characterization of the new La2SrCo2FeO9 triple perovskite material. The samples were produced by the solid-state reaction method. The analyses of the XRD patterns were made by Rietveld refinement through the GSAS code. The results reveal that the material crystallizes in an orthorhombic complex perovskite, space group Immm (#71) with lattice parameters a=5.4314(3) ?, b=5.4583(3) ? and c=7.7018(2) ?. SEM micrographs evidence a strongly diffused granular morphology with mean grain size of 2 μm and the EDX spectra show that the chemical composition of samples are in good agreement with the nominal values of the stoichiometric formula. 57Fe Mössbauer spectroscopy recorded at 300 K reveals two sites in concordance with the X-ray diffraction measurements, and its valence state is +3, as determined from the isomer shift found. At 4.2 K magnetic ordering with canting of the Fe moments is found. Measurements of the magnetization as a function of temperature permitted us to determine the ferromagnetic characteristic of material with an effective magnetic moment of 9.7μ B. 相似文献
22.
Constrained optimization is a major real-world problem. Constrained optimization problems consist of an objective function subjected to both linear and nonlinear constraints. Here a constraint handling procedure based on the fitness priority-based ranking method (FPBRM) is proposed. It is embedded into a harmony search (HS) algorithm that allows it to satisfy constraints. The HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. Here, the original heuristic HS was improved by combining both improved and global-best methods along with the FPBRM. The resulting modified harmony search (MHS) was then compared with the original HS technique and other optimization methods for several test problems. 相似文献
23.
Anees A. Khadom Hongfang Liu Ahmed A. Fadhil Abdul Mun’em A. Karim 《Oxidation of Metals》2016,86(5-6):553-565
The high-temperature corrosion rate of boiler tubes was studied as a function of inhibitor concentration, time, and temperature in the absence and presence of fuel ash. Samples of steel tubes were taken from boilers that operate in Northern Baghdad Station for Electric Power Generation. Fuel ash was collected from the boiler combustion chamber, as well. Normal and nano-MgO were used as a corrosion inhibitor in different mixing ratios. A weight loss technique was used to evaluate the corrosion rates, while scanning electron microscopy was used to study the surface morphology. It was seen that corrosion rates increased with both time and temperature, and decreased with the addition of inhibitors. The maximum inhibitor efficiency was 81 %, obtained via using nano-MgO at mixing weight ratio 2:1, 600 °C, and 10 h. The Presence of fuel ash had harmful effects on the steel surface. 相似文献
24.
Abstract: The chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods (supercritical carbon dioxide [SC‐CO2], mechanical press, and solvent extraction) were studied. The SC‐CO2 extraction at 420 bar and 50 °C and hexane extraction showed significantly higher oil yield than mechanical press extraction (P < 0.05). The fatty acid compositions in the oils were virtually identical regardless of the extraction methods. The contents of tocopherol, sterol, policosanol, and phosphorus in the perilla oils greatly varied with the extraction methods. The SC‐CO2‐extracted perilla oils contained significantly higher contents of tocopherols, sterols, and policosanols than the mechanical press‐extracted and hexane‐extracted oils (P < 0.05). The SC‐CO2‐extracted oil showed the greatly lower oxidative stability than press‐extracted and hexane‐extracted oils during the storage in the oven under dark at 60 °C. However, the photooxidative stabilities of the oils were not considerably different with extraction methods. 相似文献
25.
26.
Kim Youngki Kwon Kiyoun Mun Duhwan 《Journal of Mechanical Science and Technology》2021,35(7):3131-3143
Journal of Mechanical Science and Technology - Three-dimensional (3D) printing technology is an excellent tool for implementing multi item, small scale production or for manufacturing objects of... 相似文献
27.
28.
As it evolves, the World Wide Web (the Web) increasingly reveals the potential to enhance new aspects of our daily lives. While some take full advantage of the Web's diverse and cutting edge offerings, others choose to limit the extent of their utilization to a small subset of the Web's available functions. Recognizing this variation, a growing body of research investigates the drivers of usage behavior on the Web. Individual differences, namely broad personality and IT-specific traits, are highlighted within this stream as important predictors of Web use. Although substantial progress has been made, an important issue still facing trait research in this area is the absence of a theory-grounded basis for inter-relating broad personality and IT-specific traits. As a result, the accumulation of extant trait research is characterized by a disjointed assortment of trait constructs lacking clear theoretical linkages with one another. Additionally, while numerous studies have investigated isolated Web usage behaviors, an important outcome that remains under-investigated is the extent of an individual's utilization of the Web overall. Addressing these issues, the current study leverages the hierarchical view of traits to develop a theory-grounded, integrative model of broad personality and IT-specific traits. After developing the hierarchical model, the integrated network of traits is positioned as a direct antecedent of Web utilization and empirically tested via a two-stage field survey of 230 Web users. The results corroborate most of the hypotheses, providing support for the hierarchical view and extending the knowledge base on Web-user behavior. Overall, this study unifies disjointed personality and IT-specific trait constructs and offers theoretical guidance for future studies, introducing a much-needed ground for cumulative tradition within this stream. 相似文献
29.
Chang Woo Shin Hyungkyoon Kim Mun Kyum Kim Wonsik Lim Suk Won Cha 《Journal of Mechanical Science and Technology》2014,28(5):1615-1621
Subjective evaluations by experienced test drivers are primarily used to assess the driveability of vehicles in automotive companies. However, these evaluations are limited in terms of repeatability, incur costs, and require much time. Therefore, this study introduces a method of quantitatively evaluating the driveability of heavy-duty vehicles to circumvent these limitations. A vehicle experiment is conducted to measure data from an electronic control unit and an accelerometer to assess the driveability of heavy-duty vehicles. The evaluation indices for driveability are selected from previous studies on the objective and subjective methods of evaluating driveability according to various driving conditions. The indices include engine start, idle, acceleration, deceleration, constant speed, and start-up driving conditions. This research presents a quantitative evaluation method using the calculated values of each index and the correlated weighting factors of indices obtained from the regression analysis of the subjective evaluations. The driveability of heavy-duty vehicles is quantitatively evaluated under various driving conditions based on the proposed method. Results of the quantitative evaluation are similar to those of the subjective evaluations, and the proposed method is determined applicable in evaluating the driveability of heavy-duty vehicles. 相似文献
30.
Ki-Young Shin Yong Hoon Rim Youn Soo Kim Hyo Shin Kim Jae Woong Han Chang Hyun Choi Kyung Suk Lee Joung Hwan Mun 《Journal of Mechanical Science and Technology》2010,24(9):1901-1909
Gait analysis using 3D motion capture systems provides joint kinematic and kinetic analysis results such as joint relative
angles and moments that can be use used to evaluate the degrees of pathological gait patterns. However, the complex data produced
using these 3D motion capture systems can only analyzed by experts, because the gait analysis is highly coupled to the kinematics
of each joint. Therefore, several Several previous studies using gait analysis have relied on the data compression technique
to represent gait deviation from the average normal profiles as a single value. Even though it is important to evaluate gait
pathologies at the joint level, all these previous studies have just used a single value to evaluate the pathological gait
pattern. Using just one variable for evaluation of a gait is limited in terms of determining which joint movement patterns
are getting better during rehabilitation. Therefore, in this study, a method suitable for evaluating gait deviation during
a gait was developed to provide three indices for the hip, knee and ankle joints. In addition, to validate the proposed method
in clinical cases, experimental tests were conducted on thirty thirty-six normal walkers and six patients with cerebral palsy.
Furthermore, to validate the proposed method in regards to rehabilitation, experimental tests were conducted on three classified
walking groups with imposed ankle equinus constraints. The JNI for the hip joint, knee joint and ankle were 8.78 (±3.70),
2.92 (±3.25) and 8.79 (±4.38), respectively, in the normal walking group. However, these values were significantly different
for the pathological walking group with cerebral palsy. The JNI of the hip joint, knee joint and ankle joint were 203.73 (±171.59),
81.23 (±52.13) and 248.39 (±149.99), respectively, for this group. There were also differences between any two of the three
classified groups with imposed ankle equinus constraints. In particular, the JNI of the ankle joint was statistically different
at the p<0.01 level, and this parameter clearly increased as the degree of the imposed ankle equinus was increased. These
results demonstrate that the proposed JNI can be used as a scalar factor to evaluate the angular deviation of each joint in
normal and patient groups. In addition, this approach can be adapted to evaluate rehabilitation and pre/post surgery. 相似文献