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排序方式: 共有141条查询结果,搜索用时 15 毫秒
1.
M. Liess R. Hua K. Elsenaar 《The International Journal of Advanced Manufacturing Technology》2002,20(1):58-62
Cables to moving parts on a linear actuator in production machines, such as pick-and-place machines, are a source of unreliability
owing to the possible breaking of a cable. They further reduce the positioning precision of the actuator owing to additional
forces. Slotted waveguide systems for rail vehicles based on 2.4 GHz transmission frequency are well known, but transmitters/receivers
and waveguides are bulky. The paper reports on the reduction in size of the equipment, adapted to 5.8 GHz using a commercial
off-the-shelf RadioLan communication module. Further, the efficient termination of the wave-guide and a new way to reduce
standing-wave effects is also discussed. 相似文献
2.
The moisture contents of coals are often too high and need to be reduced before further processing. In this study, the application of microwave radiation as an alternative energy source for the drying of a sub-bituminous coal was investigated. Firstly, the permittivities of the coal were evaluated as a function of temperature and frequency. Secondly, the drying kinetics were studied in a 2.45 GHz microwave system and the effects of incident microwave power, sample mass and initial moisture contents were determined. The results demonstrated that microwave drying had several advantages over conventional drying such as increased drying rates and lower final moisture contents. In some tests, magnetite was added as a susceptor to increase the drying rates. Thirdly, the drying data were fitted to ten exponential decay models, and although reasonable agreement was observed with all the models, the best fit was obtained with the Midilli–Kucuk model. Finally, the effective diffusion coefficients of moisture and also the activation energy of the diffusion process were estimated and used to further elucidate the mechanism of microwave drying. 相似文献
3.
Chemikalienfreie Bekämpfung von Holzschädlingen durch dielektrische Erwärmung mit Radiowellen und Mikrowellen 下载免费PDF全文
Christian Hoyer Christian Pfütze Dr. Rudy Plarre Dr. Ulf Trommler Steffen Steinbach Kerstin Klutzny Dr. Frank Holzer Carsten Rabe Björn Höhlig Prof. Frank‐Dieter Kopinke Prof. Detlef Schmidt Dr. Ulf Roland 《化学,工程师,技术》2014,86(8):1187-1197
Thermal pest control requires long treatment times due to the low thermal conductivity of wood and may lead to the formation of cracks. Here, the thermal treatment with radio waves as well as microwaves has been studied. The direct dielectric heating has the advantage of a good homogeneity. The obtained temperature profiles for radio waves were more homogeneous compared to microwaves. Detailed studies showed that elimination of pests was not related to the application of the electromagnetic field itself, but due to the temperature increase. 相似文献
4.
Zaishan Wei Guihua Zeng Zhirong Xie Jianliang Sun 《Canadian Metallurgical Quarterly》2010,136(12):1403-1408
FeCoCu/zeolite 5A was used as a catalyst for microwave catalytic desulfurization and denitrification and for microwave catalytic reduction of SO2 and NOx with ammonium bicarbonate (NH4HCO3) as a reducing agent. Microwave catalytic desulfurization and denitrification efficiency attained 99.5 and 86.1%, respectively. The reaction efficiencies of microwave catalytic reduction of SO2 and NOx could be up to 95.8 and 95.1% separately; the optimal microwave power and empty bed residence time on microwave catalytic reduction of SO2 and NOx simultaneously are 280 W and 0.358 s, respectively. Microwave accentuates catalytic reduction treatment, and microwave addition can increase the SO2 and NOx removal efficiency. The microwave catalytic SO2 and NOx removal follows the Langmuir-Hinshelwood model. 相似文献
5.
6.
WeiJia Luo LingXia Li Shihui Yu Qianyu Guo Bowen Zhang Zheng Sun 《Ceramics International》2018,44(11):12414-12419
Low-loss (Zn1-xNix)ZrNbTaO8 (0.02?≤?x?≤?0.10) ceramics possessing single wolframite structure are initiatively synthesized by solid-state route. Based on the results of Rietveld refinement, complex chemical bond theory is used to establish the correlation between structural characteristics and microwave performance in this ceramic system. A small amount of Ni2+ (x?=?0.06) in A-site with the fixed substitution of Ta5+ in B-site can effectually raise the Q?×?f value of ZnZrNb2O8 ceramic, embodying a dense microstructure and high lattice energy. The dielectric constant and τf are mainly affected by bond ionicity and the average octahedral distortion. The (Zn0.94Ni0.06)ZrNbTaO8 ceramic sample sintered at 1150?°C for 3?h exhibits an outstanding combination of microwave dielectric properties: εr =?27.88, Q?×?f?=?128,951?GHz, τf =?–39.9?ppm/°C. Thus, it is considered to be a candidate material for the communication device applications at high frequency. 相似文献
7.
Microwave radiation is a novel energy source to drive chemical reactions. In conventional reactors, however, the heat created either escapes through uninsulated reactor walls, or the microwave radiation is attenuated by insulated walls. Here, microwave selective heating of Pd catalyst particles supported on activated carbon particulates was examined in a fixed‐bed reactor using a novel vacuum‐filled Dewar‐like double‐walled continuous‐flow reactor. This reactor was developed toward energy savings in performing such organic reactions as the transformation of the hydride methyl cyclohexane to toluene. 相似文献
8.
A series of supported catalysts has been obtained by grafting of chemically generated palladium nanoparticles onto basic, Cs+ ion-exchanged molecular sieves (Al)MCM-41 and onto the non-basic, parent material MCM-41. Catalytic activity of the catalysts has been investigated in the Heck reaction between bromobenzene and butyl acrylate under microwave irradiation. The activity of the bifunctional catalysts (Pd@Cs+-(Al)MCM-41) and the activity of Pd@MCM-41 combined with sodium acetate as an external base were considerably higher under microwave irradiation than activities observed for the same catalytic systems under the conventional heating. The Pd@MCM-41/NaOAc system showed higher conversions than the bifunctional catalysts presumably due to a different nature and accessible amount of the base. On the other hand, microwave irradiation seems to increase the rate of aggregation of the metallic particles and thus also catalyst deactivation as compared with the usual heating. 相似文献
9.
Peroxidase and polyphenol oxidase thermal inactivation by microwaves in green coconut water simulated solutions 总被引:2,自引:0,他引:2
Enzymes from coconut water such as peroxidase (POD) and polyphenol oxidase (PPO) when in contact with oxygen begin reactions causing nutritional and color losses. Solutions simulating the chemical constituents of coconut water were submitted to a batch process in a microwave oven. PPO and POD inactivation data could be characterized by: PPO/water D93 °C=16.5 s (z=35.5 °C); PPO/sugars D91 °C=18 s (z=33°C); POD/water D91.5 °C=44 s (z=24 °C) and POD/sugars D92 °C=20.5 s (z=19.5 °C). The contact between salts and enzymes promoted a drastic reduction of the initial activity. After the incidence of microwave energy at temperatures above 90 °C, enzymes activity was not detected. These results can indicate an adequate choice of temperature conditions to inactivate coconut water enzymes. The knowledge of how green coconut water constituents influence POD and PPO activity will supply useful information about microwave processing of coconut water. 相似文献
10.
Dielectric spectroscopy studies have been performed on fresh and osmotically dehydrated Granny Smith apples. The osmotic treatment consisted on immerse the samples into 65% (w/w) sucrose aqueous solution at 30 °C during different exposure times lasted from 3 h to 16 days. Some physical-chemical parameters were measured in fresh, treated and reposed (24 h at 30 °C) samples. Dielectric spectra were measured in the frequency range from 500 MHz to 20 GHz by an Agilent 85070E Open-ended Coaxial Probe connected to an Agilent E8362B Vector Network Analyzer in the fresh, treated and reposed samples. It has been demonstrated that the dielectric properties are a good tool to control the surface water activity by using the loss factor at relaxation frequency. This relation of dielectric properties with the water activity allows controlling the shrinkage level and determines the moment when the driving forces change from diffusional to mechanical behaviors. This value corresponds to 12.25 ± 0.16 and represents a practical control value to decide if the final dehydrated samples shrink or swell. Moreover, the quantity of adsorbed water was estimated by the subtraction between the overall moisture and the water content in liquid phase estimated by using dielectric loss factor at relaxation frequency. 相似文献