Measurement of acoustic field radiated by low frequency power ultrasonic transducer with laser-interferometer

Based on the piezo-optic effect of medium, the refractive index of medium is the function of its density, and so it's also the function of acoustic pressure. Therefore, acoustic pressure in the optical path everywhere can be determined absolutely by laser-interferometric technique and relative distribution of pressure in the middle and far acoustic field, which can be obtained from theory or experiment respectively. Theory and experiment of measurement of pressure in acoustic field with laser-interferometer are introduced. Distribution of pressure radiated by a power ultrasonic transducer is determined by laser interferometric technique. The theoretical and experimental results are in good agreement. The receiving sensitivity of a PVDF (Polyvinylidene fluoride) transducer in free field is also calibrated absolutely due to above results and its sensitivity is -118.5 dB.

Improving Dynamic Stability of Yunnan Provincial and South China Power System by PSS

For solving the dynamic instability problem of Yunnan Provincial Power System (YNPS) and the South China Interconnected Power System (SCIPS), Lubuge Hydropower Station was chosen to install Power System Stabilizer (PSS). This paper introduces the principles and methods of parameter selection for PSS, in addition to field test. The test results show that the PSS installed can significantly improve the system damping.

Design theory and experimental investigation of the low frequency and high power rare earth magnetostrictive flextensional transducer (Ⅰ). Theoretical part

The energy relationships among all the elements, by which the magnetostrictive transducers are manufactured, in Finite Element Method (FEM) are analyzed, then the expres- sions of FEM dynamics equations and performances formulas for magnetostrictive transducers are derived. The vibrating modes of the class VII transducer and its shell vibration are calcu- lated theoretically and the results point out that there is a breathing mode and if the transducer works at this mode, the transducer will vibrate with a greater volume speed and source level.

Design theory and experimental investigation of the low frequency and high power rare earth magnetostrictive flextensional transducer (Ⅱ). Experimental part

Vibrating modes of the manufactured flextensional transducer and its shell are experimentally investigated. The result are consistent with the theoretical calculations. The acoustical performances for the transducer are measured: resonance frequency is 1.16 kHz in the underwater, bandwidth is 680 Hz, mechanical quality factor is 1.71, transmitting current response is 186.1 dB, electromechanical efficiency is 13.1%.

Pulse swallowing frequency divider with low power and compact structure

A pulse swallowing frequency divider with low power and compact structure is presented.One of the DFFs in the divided by 2/3 prescaier is controlled by the modulus control signal,and automatically powered off when it has no contribution to the operation of the prescaier.The DFFs in the program counter and the swallow counter are shared to compose a compact structure,which reduces the power consumption further.The proposed multi-modulus frequency divider was implemented in a standard 65 nm CMOS process with an area of 28×22μm;.The power consumption of the divider is 0.6 mW under 1.2 V supply voltage when operating at 988 MHz.

DISCREPANCY IN SOUND POWER DETERMINATION AT LOW FREQUENCIES

The determination of the sound power of a source is simple in a reverberation chamber , but usually lower valves are obtained at low frequencies than the free - space value . It is shown that the sound power determined in a reverberation chamber depends not only on its free - space power , but also on the positions of the source and the reveiver , as well as the way the measurements are made and averaged . Exact and statistical formulas are derived to account for these factors . The results explain the discrepancy and agree well with earlier experiments . Based on the theory ,parcticable techniques of sound power determination are proposed and correct power formulas presented .

22 nm In0.75Ga0.25As channel-based HEMTs on InP/GaAs substrates for future THz applications

In this work,the performance of Lg = 22 nm In（0.75）Ga（0.25）As channel-based high electron mobility transistor（HEMT） on InP substrate is compared with metamorphic high electron mobility transistor（MHEMT） on GaAs substrate.The devices features heavily doped In（0.6）Ga（0.4）As source/drain（S/D） regions,Si double δ-doping planar sheets on either side of the In（0.75）Ga（0.25） As channel layer to enhance the transconductance,and buried Pt metal gate technology for reducing short channel effects.The TCAD simulation results show that the InP HEMT performance is superior to GaAs MHEMT in terms of fT,f（max） and transconductance（g（mmax））.The 22 nm InP HEMT shows an fT of 733 GHz and an f（max） of 1340 GHz where as in GaAs MHEMT it is 644 GHz and 924 GHz,respectively.InGaAs channel-based HEMTs on InP/GaAs substrates are suitable for future sub-millimeter and millimeter wave applications.