Local Hardening Evaluation of Carbon Steels by Using Frequency Sweeping Excitation and Spectrogram Method

We use steel materials for a car, an industrial machine, a building and so on. The steel materials are used for the main parts of the machine. The steel materials have good mechanical characteristics, however, higher mechanical characteristics by special treatment are often demanded. In this case, some evaluation methods are also required to monitor and control the mechanical characteristics of steel materials. Normally, mechanical destructive testing is used for the evaluation of them, however, all products on line cannot be evaluated because destructing samples are needed by mechanical testing. Therefore, non-destructive evaluation by electromagnetic method is focused on in this paper. We have developed a non-destructive evaluation for hardening steel named as a frequency sweep excitation and spectrogram (FSES) method [1]. This proposed method can evaluate mechanical characteristics non-destructively by using several frequency components of magnetic flux depending on hardening conditions [1]. Figure 1 shows the measured magnetic coercive force Hc and maximum magnetic field strength Hmax. The sample were hardened by induction heating with the current of 80[A]. As shown in Figure 1, in the 8 - 12 [mm] and 16 - 22 [mm] sections, the spectrogram of the maximum magnetic field strength Hmax was changed locally in comparison of the one of the magnetic coercive force Hc. It has been made clear that the magnetic coercive force Hc could evaluate the hardening strength qualitatively and quantitatively [1]. Moreover, it is obvious that the local material changes can be evaluated by the maximum magnetic field strength Hmax as shown in Figure 1

Electron emission from conduction band of diamond with negative electron affinity

Experimental evidence explaining the extremely low-threshold electron emission from diamond reported in 1996 has been obtained for the first time. Direct observation using combined ultraviolet photoelectron spectroscopy/field emission spectroscopy (UPS/FES) proved that the origin of field-induced electron emission from heavily nitrogen (N)-doped chemical vapour deposited (CVD) diamond was at conduction band minimum (CBM) utilising negative electron affinity (NEA). The significance of the result is that not only does it prove the utilisation of NEA as the dominant factor for the extremely low-threshold electron emission from heavily N-doped CVD diamond, but also strongly implies that such low-threshold emission is possible from other types of diamond, and even other materials having NEA surface. The low-threshold voltage, along with the stable intensity and remarkably narrow energy width, suggests that this type of electron emission can be applied to develop a next generation vacuum nano-electronic devices with long lifetime and high energy resolution.Comment: 17 pages, 4 figures, Phys. Rev. B in pres

Dissipative hydrodynamic equation of a ferromagnetic Bose-Einstein condensate: Analogy to magnetization dynamics in conducting ferromagnets

The hydrodynamic equation of a spinor Bose-Einstein condensate (BEC) gives a simple description of spin dynamics in the condensate. We introduce the hydrodynamic equation of a ferromagnetic BEC with dissipation originating from the energy dissipation of the condensate. The dissipative hydrodynamic equation has the same form as an extended Landau-Lifshitz-Gilbert (LLG) equation, which describes the magnetization dynamics of ferromagnets interacting with spin-polarized currents. Employing the dissipative hydrodynamic equation, we demonstrate the magnetic domain pattern dynamics of a ferromagnetic BEC in the presence and absence of a current of particles, and discuss the effects of the current on domain pattern formation. We also discuss the characteristic lengths of domain patterns that have domain walls with and without finite magnetization.Comment: 19 pages, 5 figure