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排序方式: 共有286条查询结果,搜索用时 15 毫秒
51.
Tanjore V. Jayaraman Laura BooneJeffrey E. Shield 《Journal of Alloys and Compounds》2011,509(5):1411-1417
A series of Gd100−xMnx (x = 0, 5, 10, 15, and 20 at.%) alloys were prepared by arc-melting. The Curie temperature (TC) associated with the ferromagnetic-paramagnetic transitions, derived from M-T curves, show decrease in TC for as-cast alloys (∼279 K) as compared to as-cast Gd (∼292 K). No appreciable decrease in the |ΔSM|max values ∼4.6 J/kg K (0-2 T) and ∼8.6 J/kg K (0-5 T) were observed upon alloying Gd with Mn up to x ≤ 15 at.%. Refrigerant capacity (q) showed negligible variation ∼195 J/kg (0-2 T) and ∼450 J/kg (0-5 T) with increasing Mn (up to x ≤ 15 at.%) content. Similar values of |ΔSM|max and q coupled with ∼13 K decrease in TC for as-cast Gd100−xMnx (0 ≤ x ≤ 15) alloys as compared to Gd, suggests expansion of working temperature region of Gd upon alloying with Mn up to 15 at.%. Low cost, adjustable TC, favorable magnetocaloric properties make Gd100−xMnx alloys potential candidates as second-order transition based magnetic refrigerants for near room temperature air-conditioning and magnetic refrigeration. 相似文献
52.
C. R. Mariappan K. I. Gnanasekar V. Jayaraman T. Gnanasekaran 《Journal of Electroceramics》2013,30(4):258-265
Electrical properties of the lithium garnets Li5La3Ta2O12 (L5LTO) and Li7La3Ta2O13 (L7LTO) are reported over a wide frequency range from 10 MHz to 0.1 Hz at different temperatures. The structural properties are characterized by powder X-ray diffraction, Scanning electron microscopy with energy dispersive X-ray spectroscopy and Fourier transformation Infrared spectroscopy. By means of the frame work of classical brick layer model (BLM) and of a finite element approach, the ion transport properties of grain and grain boundary for the lithium garnets were analyzed. The specific grain conductivity of 5.0?×?10?6?S/cm at 40 °C is found for both lithium garnets. Specific grain conductivities and grain boundary conductivities are thermally activated, with activation energies found to be in the range of 0.55–0.61 eV. The total conductivity is found to be depending on the ion conduction of grain boundary. The information on the fraction of contact area αcontact between grains <0.25 is obtained by the finite element approach for Li7La3Ta2O13. 相似文献
53.
In friction stir welding (FSW), the material under the rotating action of non-consumable tool has to be stirred properly to get defect free welds in turn it will improve the strength of the welded joints. The welding conditions and parameters are differing based on the mechanical properties of base materials such as tensile strength, ductility and hardness which control the plastic deformation during friction stir welding. The FSW process parameters such as tool rotation speed, welding speed and axial force, etc. play a major role in deciding the weld quality. FSW Joints of cast aluminium alloys A319, A356, and A413 were made by varying the FSW process parameters and the optimum values were obtained. In this investigation, empirical relationships are established and they can be effectively used to predict the optimum FSW process parameters to fabricate defect free joints with high tensile strength from the known base metal properties of cast aluminium alloys. 相似文献
54.
P. Rangaswamy M. R. Daymond M. A. M. Bourke R. Von Dreele K. Bennett N. Jayaraman 《Metallurgical and Materials Transactions A》2000,31(13):889-898
Residual strain and texture variations were measured in two titanium matrix composites reinforced with silicon carbide fibers
(Ti/SiC) of similar composition but fabricated by different processing routes. Each composite comprised a Ti-6242 α/β matrix
alloy containing vol 35 pct continuous SiC fibers. In one, the matrix was produced by a plasma sprayed (PS) route, and in
the other by a wiredrawn (WD) process. The PS and WD composites were reinforced with SCS-6 (SiC) and Trimarc (SiC) fibers,
respectively. The texture in the titanium matrices differed significantly. The titanium matrix for the PS material exhibited
random texture pre and post fabrication of the composite. For the WD material, the starting texture of the monolithic titanium
matrix was ≈17 times random, but after consolidation into composite form, it was ≈6 times random. No significant differences
were noted in the fiber-induced matrix residual strains between the composites prepared by the two procedures. However, the
Trimarc (WD) fibers recorded higher (≈1.3 times) compressive strains than the SCS-6 (PS) fibers. Stresses and stress balance
results are reported. Plane-specific elastic moduli, measured in load tests on the unreinforced matrices, showed little difference.
This article is based on a presentation made in the Symposium “Mechanisms and Mechanics of Composites Fracture” held October
11–15, 1998, at the TMS Fall Meeting in Rosemont, Illinois, under the auspices of the TMS-SMD/ASM-MSCTS Composite Materials
Committee. 相似文献
55.
Most plastic packaging products are discarded after a single use resulting in an abundant supply of waste plastics. Natural fibres are light in weight, abundant and inexpensive. The stiffness and strength of polymers have been shown to improve with the incorporation of natural fibres. Hence, composite materials made of natural fibres and waste plastics would result in the reduction of plastic wastes and the use of fibres from renewable resources. Composite specimens and sheets consisting of fibres from the New Zealand flax plant, phormium tenax or Harakeke as it is known in Maori, and waste plastics have been produced through screwless extrusion followed by injection moulding. The tensile and impact properties of these composites have been determined. The formability of these composites has been assessed through thermoforming. 相似文献
56.
This paper investigates the nexus between economic growth and oil price in small Pacific Island countries (PICs). Except Papua New Guinea, none of the 14 PICs has fossil any fuel resources. Consequently, the other 13 PICs are totally dependent on oil imports for their economic activities. Since PICs have limited foreign exchange earning capacities, as they have a very narrow range of exports and are highly dependent on foreign aid, high oil prices in recent months have seriously tested their economic resilience. This paper applies the ARDL bounds testing methodology to four selected PICs, Samoa, Solomon Islands, Tonga and Vanuatu, which have consistent and reliable time series of data, with a view to assess the impact of oil price on economic growth. The findings are that oil price, gross domestic product and international reserve are cointegrated in all the four PICs. Further, both in the long and short runs, we observe that there is a uni-directional relationship as causality linkage runs only from oil price and international reserves to economic growth. The paper makes some policy recommendations. 相似文献
57.
Hierarchical 3D Cobalt‐Doped Fe3O4 Nanospheres@NG Hybrid as an Advanced Anode Material for High‐Performance Asymmetric Supercapacitors 下载免费PDF全文
Meng Guo Jayaraman Balamurugan Xuyang Li Nam Hoon Kim Joong Hee Lee 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(33)
Hierarchical nanostructure, high electrical conductivity, extraordinary specific surface area, and unique porous architecture are essential properties in energy storage and conversion studies. A new type of hierarchical 3D cobalt encapsulated Fe3O4 nanosphere is successfully developed on N‐graphene sheet (Co?Fe3O4 NS@NG) hybrid with unique nanostructure by simple, scalable, and efficient solvothermal technique. When applied as an electrode material for supercapacitors, hierarchical Co?Fe3O4 NS@NG hybrid shows an ultrahigh specific capacitance (775 F g?1 at a current density of 1 A g?1) with exceptional rate capability (475 F g?1 at current density of 50 A g?1), and admirable cycling performance (97.1% capacitance retention after 10 000 cycles). Furthermore, the fabricated Co?Fe3O4 NS@NG//CoMnO3@NG asymmetric supercapacitor (ASC) device exhibits a high energy density of 89.1 Wh kg?1 at power density of 0.901 kW kg?1, and outstanding cycling performance (89.3% capacitance retention after 10 000 cycles). Such eminent electrochemical properties of the Co?Fe3O4 NS@NG are due to the high electrical conductivity, ultrahigh surface area, and unique porous architecture. This research first proposes hierarchical Co?Fe3O4 NS@NG hybrid as an ultrafast charge?discharge anode material for the ASC device, that holds great potential for the development of high‐performance energy storage devices. 相似文献
58.
Meenakshi Jayaraman 《International Journal of Electronics》2020,107(2):310-330
ABSTRACTThis work introduces a new passive filter structure for a pulse width modulated inverter used in standalone applications. The proposed structure consists of an additional capacitor connected across the resistance-capacitance branch of the traditional LCR filter and an additional resistor connected across the trap filter capacitor in the traditional (LC)trap-LCR filter configuration which helps to reduce damping power loss and increase harmonic attenuation while maintaining the same overall filter size of conventional filters. A comprehensive parameter design procedure of the proposed filter is introduced which considers inverter switching frequency and choice of damping components. Further, particle swarm optimisation algorithm is newly employed in this work to minimise resonant peaking on the premise of allowable values of overall filter inductance, capacitance and resistance. Simulation and experimental results are presented to analyse the performance of the proposed filter and a comparison is established with other passive filter topologies. A five-level inverter with the proposed filter is implemented using a SPARTAN- 6 XC6SLX25 processor on an experimental set-up. The experimental results show an attractive performance of the proposed filter in providing improved inverter output waveforms, significant harmonic reduction in the high-frequency band, reduced resonant peaking, lesser harmonic distortion and lower damping power loss. 相似文献
59.
Krishnamoorthy Jayaraman David Velayutham Ramanujam Kanakam Srinivasan Sankaranarayanan Chidambaram 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(6):626-631
An industrial solution of ethylenediamine hydrochloride which contains about 18% chloride and 12% amine was electrodialysed in a five‐compartment cell to obtain pure ethylenediamine. Different parameters such as alkali concentration and current density were studied to optimise conditions of maximum current efficiency for amine recovery and chloride removal from the feed solution. The Suitabilities of different ion‐exchange membranes for electrodialysis were compared. Variation in current efficiency for amine recovery with increases in the concentration of amine during electrodialysis was also studied. Current efficiency for amine recovery and chloride removal is about 78% and 91% respectively under optimum conditions. The amount of electrical energy consumed is 12.1 kWh kg?1 for ethylenediamine recovery and 8.6 kWh kg?1 for chloride removal. The concentration of pure amine obtained after the electrodialysis was around 20%. The results are encouraging for industrial applications whereby ethylenediamines free from chlorides can be isolated. Copyright © 2003 Society of Chemical Industry 相似文献
60.