Winter tornadic storms over the Japan Sea area have been observed during the Shonai Area Railroad Weather Project between 2007 and present. The MRI portable X-band Doppler radar has been installed on the roof of Shonai Airport building in Sakata City during this project. On 25 January 2008, a winter tornado passed very close to the radar near the coast. In this paper, the detailed vertical structures of the high-resolution reflectivity and velocity fields of this tornado during landfall are described. Before landfall, the reflectivity field revealed that the center of the tornado had a weak-echo "eye" partially surrounded by an eyewall. After landfall, the eyewall was transformed to spiral structures spiraling outward from the eye. The diameter of the maximum tangential wind contracted from 582 m to 291 m at the height near 150 m. The radar data indicate that the tornado was tilted downstream and the diameter increased with height. The results in the present study will be reflected the information of radar signatures from a winter tornado, which can contribute to the refinement of future wind gust algorithms concerning operational use.
Thermal barrier coating (TBC) is applied to high temperature conditions in gas turbines, such as rotor blades and combustors, to protect the metal substrate surface against hot gas flow. The surface roughness of TBC is reported to affect the heat transfer coefficient, so surface roughness measurement is necessary for improving the thermal analysis of TBS. In this report, terahertz waves were used to measure the surface roughness of TBC specimens. An analytical one-dimensional model based on time of flight was constructed to confirm that the reflection characteristics of a terahertz wave pulse generated by a photoconductive antenna obey the Debye-Waller factor. The surface roughness of five TBC specimens fabricated by the same process was measured to be 16±2µm, which was in agreement with the microscopic observation result of the surface profile of a TBC specimen fabricated in the same lot. These results showed that terahertz waves are effective for measuring the surface roughness of TBC.
Hardware Trojans (HT) that are implemented at the time of manufacturing ICs are being reported as a new threat that could destroy the IC or degrade its security under specific circumstances, and is becoming a key security challenge that must be addressed. On the other hand, since it is also common to use components manufactured or bought via third parties in portions outside of the substrate on which the IC is mounted or communication lines connecting the IC and the substrate, there is a possibility that HTs may also be set in the peripheral circuits of the IC in the same manner as in the IC. In this paper, we developed an HT that could be implemented in the peripheral circuits and wiring of an IC, investigated the possibility of being able to acquire information processed inside a device by measuring the electromagnetic waves generated and leaked by Intentional Electromagnetic Interference (IEMI) with HT outside the device, and investigated detection methods for cases where such HTs are implemented.
Two dimensional reflection intensity distributions of terahertz wave intensity provide a direct transparent image of corrosion beneath opaque anticorrosion paint layers. However, attention needs to be paid to changes in effective reflectivity due to uneven surfaces. This study demonstrates in-situ estimation of surface roughness and reflective index by frequency analysis of the terahertz wave form reflection echoes. Deconvolution technique is applied to resolve the undulation of the waveform to separate the overlapping of the reflections from the front and back surfaces of the paint. Estimated and measured roughness values are in good agreement, to show roughness and refractive index distribution of a service-used transmission tower cross-arm.
We studied an oversized W-band (75 - 110 GHz) surface wave oscillator driven by a weakly relativistic electron beam. Surface wave is formed on slow wave structure (SWS) with rectangular corrugations and has an upper-cutoff frequency of about 100 GHz. To excite the surface wave, an annular electron beam is generated by a disc type cold cathode with beam energy between about 10 and 80 keV. The oscillator is driven in the backward wave oscillator (BWO) region for beam energy less than 30 keV and in the traveling wave tube (TWT) region for beam energy more than 30 keV. In the BWO region, microwaves are generated due to Cherenkov interaction between electron beam and surface wave in the W-band. In the TWT region, two types of microwaves are generated. One is due to the W-band surface wave as in the case of the BWO region. The other is due to higher order modes above 140 GHz.
Far-IR absorption spectra at frequencies from 0.5 to 21.0 THz were obtained for sheets of ethylene-vinyl acetate copolymer (EVA) containing different contents of vinyl acetate (VA) from 12 to 60% with different thicknesses from 1.0 to 3.0 mm. As a result, EVA exhibits absorption at 2.5, 6.7, 10.5, 11-17, and 17-20 THz. Especially, the 2.5-THz intensity with a good proportionality up to 60% of VA content exhibits comparable accuracy to the IR method and is applicable for estimating the VA content in EVA sheets 2.0 or 3.0 mm thick, for which IR method is difficult to be applied.
Toshiba has developed solid insulated switchgear (SIS) which insulates the main circuit with epoxy composites. The solid insulating system is able not only to use no SF6, which is a kind of global warming gas, but also to supply compact equipment. In SIS, heat generated by the current loss in the conductors is dissipated through the epoxy composite. Therefore, development of high thermal conductive epoxy composites has been desired with respect to large current class SIS such as 2500 A. In this paper, epoxy composite was filled with MgO having high thermal conductivity and SiO2 having low thermal expansion coefficient. The result of temperature rise analysis of 40.5 kV - 2500 A SIS demonstrated that the high thermal conductive epoxy composite reduced rising temperature by approximately 10 K compared to conventional epoxy composite.
By the present, uniform electric field region of the sphere gap is utilized for the high tension proofreading. Generally, the discharge voltage is difficult to get stabilized discharge voltage, when spherical electrode is used. Especially, beginning of use is discharged low-voltage, when there was long-time unused hour of spherical electrode, since there is a position which is easy to discharge the electron. Such discharge is known as an irregular discharge phenomenon. Therefore, pre-discharge, etc. is done near in the use.
In this report, the relationship between applied voltage downtime and ULD was investigated as a factor of irregular discharge phenomenon from the viewpoint of ultraviolet radiation linear discharge (ULD).
The activated carbon particles made of charcoal by using an alkaline activation method were applied to the EDLC electrodes. The EDLC cells were assembled with 34% KOH water electrolyte. The density of energy was approximately 2.7Wh/L in the EDLC cells. The EDLC units (12V-EDLC) were composed of the 12 pieces of charcoal EDLC cell in a series connection. An electric power storage (1kWh class EDLC) was composed from the 30 pieces of 12V-EDLC unit in a parallel connection. The electric power storage quantity of the 1kWh class EDLC was approximately the summation of the composed 12V-EDLCs of power storage on design. The internal resistance of the composed 1kWh class EDLC was only 13mΩ. From the obtained results, there is a possibility of the over 1kWh class EDLC with low internal resistance is also composed of charcoal EDLCs.