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1.
高灵敏度的光纤光栅压强传感器   总被引:14,自引:0,他引:14  
基于光纤布拉格光栅传感模型 ,提出了一种等强度梁与波纹管相结合的高灵敏度的光纤布拉格光栅压强传感器 ,推导了光纤布拉格光栅反射波中心波长相对偏移量与压强之间的解析关系式 ,从理论和实验上给出了压强灵敏度系数。该传感器的理论和实验压强灵敏度系数分别是 1.4 76× 10 -2 MPa-1、1.35× 10 -2 MPa-1,是裸光纤光栅的 74 5 5倍和 6 80 8倍 ,理论值与实验值吻合得很好。同时指出通过调节等强度梁和波纹管的参量 ,可以将该传感器的压强灵敏度系数做得很高 ,直至破坏了光纤布拉格光栅。  相似文献
2.
新型高准确度光纤光栅压力传感系统   总被引:12,自引:11,他引:1       下载免费PDF全文
胡志新  朱军  张陵 《光子学报》2006,35(5):709-711
提出一种使用光纤双布喇格光栅测定压力的测量方法.在外界压力作用下,传感光纤布喇格光栅反射波长的漂移,被转变成在交变力策动下,发生弯曲的等强度悬臂梁调制扫描光栅反射光脉冲间隔的变化.实验结果表明,光纤布喇格光栅反射波长漂移的测量范围为0~3 nm,波长测量的不确定度为1 pm;压力传感器的量程为0~6 MPa时,压力的测量不确定度为0.005 Mpa.  相似文献
3.
Maghemite nanoparticles covalently coated with polyethylene glycol are investigated with respect to different loss processes in magnetic AC-fields. Transmission electron microscopy reveals a narrow size distribution which may be well approximated by a normal distribution (mean diameter 15.3 nm and distribution width 4.9 nm). Aqueous ferrofluids were characterised by DC-magnetometry, by measuring susceptibility spectra for a frequency range 20 Hz to 1 MHz and by calorimetric measurements of specific loss power (SLP) at 330 and 410 kHz for field amplitudes up to 11.7 kA/m. Extremely high values of SLP in the order of 600 W/g result for 400 kHz and 11 kA/m. In addition to liquid ferrofluids measurements were performed with suspensions in gel in order to elucidate the role of Brownian relaxation. The measured susceptibility spectra may be well reproduced by a model using a superposition of Néel and Brown loss processes under consideration of the observed narrow normal size distribution. In this way the observed very high specific heating power may be well understood. Results are discussed with respect to further optimisation of SLP for medical as well as technical RF-heating applications.  相似文献
4.
彭保进  张敏  廖延彪  赖淑蓉  匡武  贺晓霞 《光子学报》2005,34(10):1501-1505
报导了用光纤布喇格光栅(FBG)传感器测量军工用的一新型材料的新方法.实验结果表明,此方法可在恶劣环境下可靠检测热膨胀系数,FBG在低至-50℃和高至+150℃大范围下仍能正常工作.文中给出了相应理论及实验结果.  相似文献
5.
高温超导体中的交流损耗   总被引:3,自引:1,他引:2  
考虑到陶瓷高温超导体的颗粒物性 ,详细研究了 Bean- london模型及 Anderson- kim模型在分析高温超导体交流损耗方面的缺陷 ,提出了一种新的计算方法。用这种方法预期的损耗规律与文献报道的实验结果一致。另外 ,分析了超导体尺寸、晶间临界电流、晶粒尺寸和晶内临界电流对高温超导体交流损耗的影响  相似文献
6.
This work investigated the magnetic losses of heat treated iron-based soft magnetic composites with a thin MgO insulating layer produced by sol-gel method. The samples were characterized by energy dispersive X-ray spectroscopy, X-ray analysis and Fourier transform infrared spectroscopy. The results show that the surface of the powders contains a thin layer of MgO insulation. The loss results indicate that the hysteresis part for both the core loss and total loss factor was approximately the same for the MgO-insulated compacts and conventional SOMALOYTM samples with phosphate insulation after annealing at 600 °C. But the MgO-insulated compacts exhibited significantly lower eddy current contribution of both core loss and total loss factor with respect to SOMALOYTM samples after annealing. Also the contribution of eddy current in the iron particles for MgO insulated compacts (kp=0.91) was noticeably higher than this contribution for SOMALOYTM samples (kp=0.18) after annealing due to the higher electrical resistivity of the MgO-insulated compacts.  相似文献
7.
Enhancement of AC-losses of magnetic nanoparticles for heating applications   总被引:2,自引:0,他引:2  
Aqueous ferrofluids of maghemite nanoparticles coated with carboxydextran were investigated with respect to their specific loss power (SLP) in dependence on frequency and field amplitude of magnetic AC-fields. In order to elucidate the effect of the size distribution on SLP fluid fractions with different mean particle core size were prepared by a magnetic separation procedure from the original ferrofluid. Structural characterisation by means of TEM and XRD as well as reconstruction of core size distributions from magnetisation curves reveals that the narrow size distributions of the fractions cover a range of mean core sizes from about 8 up to 20 nm. Spectra of the complex susceptibility were measured for a frequency range of 20 Hz to 1 MHz. From the imaginary part of the susceptibility the specific loss power is calculated in dependence on frequency. The results are compared with calorimetrical measurements performed in dependence on field amplitude up to 11 kA/m at 410 kHz. A very high specific loss power in the order of 400 W per gram maghemite was found at 410 kHz and 11 kA/m for the fluid fraction having the largest mean core diameter. A deviation from linear response behaviour is found for this sample showing a power law field dependence of the specific loss power SLPH2.5. In addition to liquid suspensions measurements were performed with particles immobilised in mannitol or gel in order to elucidate the role of Brownian relaxation. The experimentally found dependence of SLP on the mean particle core diameter may be understood in the frame of the Debye dispersion model. Results are discussed with respect to applications of ferrofluids in RF-magnetic hyperthermia.  相似文献
8.
Numerical modelings of superconducting wires for AC loss calculations   总被引:2,自引:0,他引:2  
Superconducting properties of superconducting wires as well as the influence of their composite structure and twisting should be taken into account for their numerical modeling for AC loss calculations. Furthermore, complicated electromagnetic conditions in electrical apparatuses under which superconducting wires are used influence their AC loss properties; superconducting wires carry their transport current and are exposed to the external magnetic field whose direction and magnitude vary spatially. A series of numerical models of superconducting tapes based on the finite element method has been developed. In each model, some of the above-mentioned factors that could influence the AC loss properties are taken into account. The models are formulated with the current vector potential and the scalar magnetic potential (TΩ method). Superconducting property is given by the EJ characteristic represented by a power law. The current distributions in non-twisted and twisted superconducting tapes carrying their transport current and/or exposed to the external magnetic field are calculated with these models to estimate their AC loss. The current distribution in a short piece of superconducting tape exposed to AC magnetic field is also calculated.  相似文献
9.
高温超导带材的交流损耗   总被引:2,自引:0,他引:2  
介绍了交流损耗的物理机制及其与外场强度、频率等物理量间的关系 ;给出了单芯及多芯超导体中的交流损耗的实验结果及理论描述 ;指出了交流损耗研究中尚存在的某些问题。  相似文献
10.
大型超导电缆交流损耗的计算   总被引:2,自引:0,他引:2  
给出了超导电缆交流损耗的表达式。使用这些表达式 ,并基于 HT- 7U极向场线圈系统在等离子体建立时的电流波形 ,计算了 AC损耗在 PF导体上的能量沉积。最后讨论了电缆参数对AC损耗的影响  相似文献
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