提出利用介电损失角测量谷物含水率的方法,设计了一种新型电容传感器和由激励电路、选频放大器、相敏检波电路、低通滤波电路等组成的检测系统。通过对京411小麦的试验,建立了谷物含水率与介电损失角正切值之间的分段线性关系。多次标...提出利用介电损失角测量谷物含水率的方法,设计了一种新型电容传感器和由激励电路、选频放大器、相敏检波电路、低通滤波电路等组成的检测系统。通过对京411小麦的试验,建立了谷物含水率与介电损失角正切值之间的分段线性关系。多次标定试验表明,系统重复性误差小于0.5%。针对烘干机的大滞后、变参效等特点,采用前馈加反馈的智能 PI 控制器控制出粮含水率的在线测量和调节。展开更多
The experiment samples of La 1-xSrxMn 1-yFeyO3（x=0.15, 0.20, 0.23; y=0.10, 0.12, 0.14, 0.16） were prepared by sol-gel process, and the loss tangent and absorption coefficient in the range of 2～18 GHz were measured ...The experiment samples of La 1-xSrxMn 1-yFeyO3（x=0.15, 0.20, 0.23; y=0.10, 0.12, 0.14, 0.16） were prepared by sol-gel process, and the loss tangent and absorption coefficient in the range of 2～18 GHz were measured by HP8722 net analyzing apparatus. It is found that changing the content of Sr or Fe would effect the microwave absorbing. When the thickness of La 1-xSrxMn 1-yFeyO3 is 2 mm and x=0.20, y=0.14, the capability of microwave absorbing is the best one. There are two absorption peaks; the maximum is 34 dB and effective band width with 10 dB and more reaches 6.2 GHz. When the frequency between 2～12.5 GHz dielectric loss is considered as the major loss from the loss angle picture. When the frequency gets to near 12.5 GHz the loss angle tangent increases or decreases suddenly. When the frequency between 12.5～18 GHz magnetic loss is be considered as the major loss. The resistivity of La 0.8Sr 0.2Mn 0.86Fe 0.14O3 at room temperature presents its semiconductor character, which is more beneficial to absorbing microwave.展开更多
Nanocrystalline TiO_(2) was prepared by means of a stearic acid gel method. The product was investigated by differential thermal analysis, thermogravimetric analysis, X-ray powder diffraction and transmission electron...Nanocrystalline TiO_(2) was prepared by means of a stearic acid gel method. The product was investigated by differential thermal analysis, thermogravimetric analysis, X-ray powder diffraction and transmission electronic microscopy(TEM). The results of the dielectric properties tested indicate that the dielectric constant of anatase-form nanocrystalline TiO_(2) is much higher than that of the coarse crystal. The dielectric constant of the nanocrystalline material is not related with the amplitude of an external AC field in a certain range.展开更多
文摘提出利用介电损失角测量谷物含水率的方法,设计了一种新型电容传感器和由激励电路、选频放大器、相敏检波电路、低通滤波电路等组成的检测系统。通过对京411小麦的试验,建立了谷物含水率与介电损失角正切值之间的分段线性关系。多次标定试验表明,系统重复性误差小于0.5%。针对烘干机的大滞后、变参效等特点,采用前馈加反馈的智能 PI 控制器控制出粮含水率的在线测量和调节。
基金Supported by the National Natural Science Foundation of China under Grant Nos 10525419 and 60736041, and the National Basic Research Programme of China under Grant No 2006CB921702.
文摘The experiment samples of La 1-xSrxMn 1-yFeyO3（x=0.15, 0.20, 0.23; y=0.10, 0.12, 0.14, 0.16） were prepared by sol-gel process, and the loss tangent and absorption coefficient in the range of 2～18 GHz were measured by HP8722 net analyzing apparatus. It is found that changing the content of Sr or Fe would effect the microwave absorbing. When the thickness of La 1-xSrxMn 1-yFeyO3 is 2 mm and x=0.20, y=0.14, the capability of microwave absorbing is the best one. There are two absorption peaks; the maximum is 34 dB and effective band width with 10 dB and more reaches 6.2 GHz. When the frequency between 2～12.5 GHz dielectric loss is considered as the major loss from the loss angle picture. When the frequency gets to near 12.5 GHz the loss angle tangent increases or decreases suddenly. When the frequency between 12.5～18 GHz magnetic loss is be considered as the major loss. The resistivity of La 0.8Sr 0.2Mn 0.86Fe 0.14O3 at room temperature presents its semiconductor character, which is more beneficial to absorbing microwave.
基金Supported by the NationalNaturalScience Foundation of China( No.6 0 0 74 0 31) and the Science Foundation of JilinProvince( No.2 0 0 10 319)
文摘Nanocrystalline TiO_(2) was prepared by means of a stearic acid gel method. The product was investigated by differential thermal analysis, thermogravimetric analysis, X-ray powder diffraction and transmission electronic microscopy(TEM). The results of the dielectric properties tested indicate that the dielectric constant of anatase-form nanocrystalline TiO_(2) is much higher than that of the coarse crystal. The dielectric constant of the nanocrystalline material is not related with the amplitude of an external AC field in a certain range.
