Thermo-mechanical sensitivity calibration of nanotorsional magnetometers

We report on the fabrication of sensitive nanotorsional resonators, which can be utilized as magnetometers for investigating the magnetization dynamics in small magnetic elements. The thermo-mechanical noise is calibrated with the resonator displacement in order to determine the ultimate mechanical torque sensitivity of the magnetometer.Comment: 56th Annual Conference on Magnetism and Magnetic Material

Study on segmented-rotor switched reluctance motors with different rotor pole numbers for bsg system of hybrid electric vehicles

© 1967-2012 IEEE. This paper investigates the design principles and performance optimization for segmented-rotor switched reluctance motors (SRSRMs) with different rotor pole numbers for belt-driven starter generators of hybrid electric vehicles. For the design principles, several constraints are derived for the numbers of stator and rotor poles, the dimensions, and the number of winding turns. Two SRSRMs with 16/10 and 16/14 stator/rotor poles are presented according to these principles. For the performance optimization, the two motors are optimized individually for maximizing the torque. To evaluate the effect of different segmented-rotor numbers, the overall performances of the two SRSRMs are investigated and compared. It is found that the 16/14 SRSRM has higher flux linkage and static torque. The 16/14 SRSRM exhibits higher torque and lower torque ripple at low speed operation, whereas at high speed, the 16/10 SRSRM performs better in terms of torque and power densities. Compared with the 16/14 SRSRM, the 16/10 SRSRM has higher final steady speed under the same startup condition. The 16/10 SRSRM can achieve higher steady speed under starter mode and provide higher generated power under braking mode. Moreover, the 16/10 SRSRM exhibits higher efficiency in the most feasible speed range, especially in high speed range, and it has wider high-efficiency area. Finally, a 16/10 SRSRM is prototyped and tested to validate the simulation results

Measured Constraints on Cloud Top Entrainment to Reduce Uncertainty of Nonprecipitating Stratocumulus Shortwave Radiative Forcing in the Southern Ocean

Stratocumulus cloud top entrainment has a significant effect on cloud properties, but there are few observations quantifying its impact. Using explicit 0-D parcel model simulations, initialized with below-cloud in situ measurements, and validated with in situ measurements of cloud properties, the shortwave cloud radiative forcing (SWCF) was reduced by up to 100 W m−2 by cloud top entrainment in the Southern Ocean. The impact of entrainment-corrected SWCF is between 2 and 20 times that of changes in the aerosol particle concentration or updraft at cloud base. The variability in entrainment-corrected SWCF accounts for up to 50 W m−2 uncertainty in estimating cloud forcing. Measurements necessary for estimating the impact of entrainment on cloud properties can be constrained from existing airborne platforms and provide a first-order approximation for cloud radiative properties of nonprecipitating stratocumulus clouds. These measurement-derived estimates of entrainment can be used to validate and improve parameterizations of entrainment in Global Climate Models

Study on strengthening mechanism of Ti/Cu electron beam welding

Welding-brazing method is widely used for dissimilar metals welding. However, it is becoming increasingly difficult to further improve the connection strength by controlling the formation of the transition layer. In this study, an innovative welding method referred to as adjacent welding was addressed, which greatly improved the tensile strength of Ti/Cu dissimilar joint. The strength of new joint could reach up to 89% that of copper base metal, compared to the use of a traditional welding-brazing method which strength coefficient is within the limit of 70%. In order to determine the strengthening mechanism of adjacent welding, optical microscopy, SEM, EDS and XRD were applied for the analysis of microstructure and phase structure. Furthermore, tensile strength was also tested. The results show that due to the process of remelting and reverse solidification of intermetallic compounds (IMCs) layer, a less complex and thinner IMCs layer was formed and TiCu (553 HV) with high embrittlement existing in the front of titanium substrate was changed into Ti2Cu (442 HV). Performances of joints were optimized by these changes. An interpretation module was presented for the mechanism