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121.
Adel Al Rai Elena Stojanovska Yasin Akgul Mohammad Mansoob Khan Ali Kilic Safak Yilmaz 《应用聚合物科学杂志》2021,138(7):49835
Highly porous free-standing co-poly(vinylidene fluoride)/modacrylic/SiO2 nanofibrous membrane was developed using electrically-assisted solution blow spinning method. The performance and the potential of the membrane as a lithium-ion battery separator were investigated. The addition of modacrylic enhanced the solution spinnability that resulted in defect-free membranes. Moreover, the presence of modacrylic enhanced the dimensional and thermal stabilities, while the addition of hydrophilic SiO2 nanoparticle enhanced both mechanical property and ionic conductivity. Combustion test results illustrated that the presence of modacrylic provide flame retarding property over a set of different polymeric-based membranes. Electrochemical performance results showed that the developed membrane can increase the battery capacity compared with the commercial separator. 相似文献
122.
Enhancement of thermal stability-insulation performance of hyper porous materials is the premier issue to design of novel porous thermal protection systems. Boron-containing monolithic novolac xerogels (BCNXs) were synthesized using sol–gel networking of novolac resin with hexamethylenetetramine (HMTA) and boric acid at the solvent saturated vapor atmosphere (SSVA). The aim was to elucidate the effect of higher crosslinking density and thermal stable boron containing chemical bonds on the microstructure, thermal conductivity, and thermal oxidation stability of novolac xerogels. The results of FESEM and BET analysis showed that the microstructural characteristics of xerogels are significantly depend on the HMTA and boric acid concentration. The thermogravimetric results were analyzed using characteristic kinetic temperature (CKT)-characteristic kinetic temperature range (CKTR) approximations. The effect of micromorphology of xerogels on the thermal conductivity was investigated. The effective thermal conductivity of samples were in the range of 0.031–0.048 W/m K. 相似文献
123.
The compulsion to use bioplastics has increased significantly today. One of the important aspects of plastics is their recyclability. Therefore, the important question of this research is that although bio-based compounds containing starch are sensitive to thermal-mechanical recycling processes, are such products thermally recyclable? To answer the question, polypropylene (PP)/thermoplastic starch (TPS) compound granules were extruded up to five times, and in the other part, single-extruded granules were blended at different ratios with virgin granules by extrusion. In order to characterize these samples, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, rotational disc rheometry, tensile properties, and appearance evaluation were used. The results showed that it is possible to recycle PP/TPS granules up to four times repetition of the extrusion operation and the fifth repetition also showed slight changes. There was also a blend of single-extruded granules with virgin material up to a 50:50% composition without significant variation. 相似文献
124.
Majid Alizadeh Moghadam Reza Mohammadi Ehsan Sadeghi Mohammad Amin Mohammadifar Mohammad Nejatian Maryam Fallah Milad Rouhi 《应用聚合物科学杂志》2021,138(28):50672
The effects of gum tragacanth obtained from two species of Astragalus Gossypinus (GT-G) and A. Parrowianus (GT-P) at two levels of 10% and 30% combined with cellulose nanofibers (CNF; 5%) on the physico-mechanical and structural properties of polyvinyl alcohol (PVA) nanocomposite film were investigated in this study. The water solubility and water vapor permeability of the films decreased with increasing the content of both gums, especially in the film containing 30% GT-P. The highest values of the tensile strength (39.3 MPa) and elongation at break (445%) belonged to the treatment containing 10% GT-P (90/10P/0). The FTIR and DSC analyses confirmed good interactions between GT and PVA in the 90/10P/0 treatment. SEM images indicated the dense structure of this film as the optimum treatment. Although the presence of CNF in the films containing GT-G improved some properties, especially the Young modulus, it impaired all the functional properties of nanocomposite GT-P film. 相似文献
125.
Receptance coupling for end mills 总被引:3,自引:0,他引:3
Simon S. Park Yusuf Altintas Mohammad Movahhedy 《International Journal of Machine Tools and Manufacture》2003,43(9):622
Identification of chatter free cutting conditions, the chatter stability lobes, requires a measurement of the frequency response function (FRF) of each tool mounted on the spindle. This paper presents a method of assembling known dynamics of the spindle–tool holder with an analytically modeled end mill using the receptance coupling technique. The classical receptance technique is enhanced by proposing a method of identifying the end mill–spindle/tool holder joint dynamics, which include both translational and rotational degrees of freedom. The method requires measurement of FRFs with impact tests applied on the spindle–tool holder assembly and blank calibration cylinders attached to the spindle. The spindle and tool holder characteristics are completely identified from the two experiments, and used for the mathematical prediction of FRF for end mills with arbitrary dimensions. The proposed method is experimentally proven and verified in cutting tests. 相似文献
126.
Three-dimensional (3-D) route-planning support offers a promising solution to overcome problems with wayfinding in complex indoor environments. An experiment was conducted to test the effect of 3-D route-planning support in a realistic setting, a large hospital building, during normal operation. Forty participants performed navigation tasks either with (n?=?20) or without (n?=?20) 3-D route-planning support. Support resulted in faster navigation, more use of artwork specifically installed to aid wayfinding, fewer navigation errors, less disorientation and less anxiety. In addition, participants used different strategies for wayfinding: without navigation support they used signs and route colour, but with navigation support they used not only the artwork, but also the existing furniture and other landmarks. The acceptance of 3-D route-planning support was high. Overall, the results support the value of 3-D route-planning support. 相似文献
127.
128.
Evolutionary population dynamics and grey wolf optimizer 总被引:1,自引:0,他引:1
129.
Mohammad Sadoghi Kenneth A. Ross Mustafa Canim Bishwaranjan Bhattacharjee 《The VLDB Journal The International Journal on Very Large Data Bases》2016,25(5):651-672
Multiversion databases store both current and historical data. Rows are typically annotated with timestamps representing the period when the row is/was valid. We develop novel techniques to reduce index maintenance in multiversion databases, so that indexes can be used effectively for analytical queries over current data without being a heavy burden on transaction throughput. To achieve this end, we re-design persistent index data structures in the storage hierarchy to employ an extra level of indirection. The indirection level is stored on solid-state disks that can support very fast random I/Os, so that traversing the extra level of indirection incurs a relatively small overhead. The extra level of indirection dramatically reduces the number of magnetic disk I/Os that are needed for index updates and localizes maintenance to indexes on updated attributes. Additionally, we batch insertions within the indirection layer in order to reduce physical disk I/Os for indexing new records. In this work, we further exploit SSDs by introducing novel DeltaBlock techniques for storing the recent changes to data on SSDs. Using our DeltaBlock, we propose an efficient method to periodically flush the recently changed data from SSDs to HDDs such that, on the one hand, we keep track of every change (or delta) for every record, and, on the other hand, we avoid redundantly storing the unchanged portion of updated records. By reducing the index maintenance overhead on transactions, we enable operational data stores to create more indexes to support queries. We have developed a prototype of our indirection proposal by extending the widely used generalized search tree open-source project, which is also employed in PostgreSQL. Our working implementation demonstrates that we can significantly reduce index maintenance and/or query processing cost by a factor of 3. For the insertion of new records, our novel batching technique can save up to 90 % of the insertion time. For updates, our prototype demonstrates that we can significantly reduce the database size by up to 80 % even with a modest space allocated for DeltaBlocks on SSDs. 相似文献
130.
Mohd Ayyub Khan Athar Ali Moinuddin Ekram Khan Mohammad Ghanbari 《Multimedia Tools and Applications》2016,75(23):15729-15762
In this paper, a reliable video communication system using adaptive Hierarchical QAM (HQAM) is designed to provide optimized unequal error protection (UEP) to embedded video bitstreams. Based on the relative importance of bits, video bitstream is partitioned into two priorities, namely High Priority (HP) and Low Priority (LP) substreams. Then, the optimal value of modulation (or hierarchical) parameter (α) of HQAM, which controls the relative error protection of these substreams, is selected from a pre-designed look-up table. The proposed system adapts itself by adapting the optimal α according to the varying channel condition, without changing the modulation level. This is in contrast to conventional WiMAX and LTE systems, in which dynamic switching among multiple modulations is used to adapt the varying channel conditions. This paper proposes HQAM with adaptive α as an alternative to the multiple modulation schemes. Moreover, for fixed average transmission power, receiver demodulates symbols without the knowledge of α. In order to further improve the video quality and to reduce the effects of erroneously received LP bits, the proposed system uses another level of adaptation, in which received LP bits are adaptively considered or discarded, before decoding the video, depending on the channel conditions (or optimized α). Simulation results show that proposed system can achieve significant improvement in the video quality compared to QAM based EEP scheme and non-adaptive HQAM. 相似文献