Yudhisther Kumar

A novel method to determine the acoustic impedance of membrane material

Abstract A new method is proposed for the determination of acoustic impedance of a material present in the form of a membrane. It has been successfully tried on two different types of polymer membranes, viz. PMMA membrane of thickness 0.20 mm and PET membrane of thickness 0.02 mm. Significantly, the method does not require the knowledge of either ultrasonic velocity or thickness or density of the membrane. It is based on the measurement of magnitudes at two different frequencies in the frequency spectra of double through-transmission signals with and without the membrane.

Menthone Aryl Acid Hydrazones: A New Class of Anticonvulsants

A series of ten compounds (Compounds J(1)-J(10)) of (±) 3-menthone aryl acid hydrazone was synthesized and characterized by thin layer chromatography and spectral analysis. Synthesized compounds were evaluated for anticonvulsant activity after intraperitoneal (i.p) administration to mice by maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) induced seizure method and minimal clonic seizure test. Minimal motor impairment was also determined for these compounds. Results obtained showed that four compounds out of ten afforded significant protection in the minimal clonic seizure screen at 6 Hz. Compound J(6), 4-Chloro-N-(2-isopropyl-5-methylcyclohexylidene) benzohydrazide was found to be the most active compound with MES ED(50) of 16.1 mg/kg and protective index (pI) of greater than 20, indicating that (±) 3-menthone aryl acid hydrazone possesses better and safer anticonvulsant properties than other reported menthone derivatives viz. menthone Schiff bases, menthone semicarbazides and thiosemicarbazides.

Primary measurement of total ultrasonic power with improved accuracy in rf voltage measurement

Out of the various existing ultrasonic power measurement techniques, the radiation force balance method using microbalance is most widely used in low power (below 1 W) regime. The major source of uncertainty associated with this technique is the error in ac voltage measurement applied to the transducer for the generation of ultrasonic waves. The sources that deteriorate the ac voltage measurement accuracy include cable length and impedance mismatch. We introduce a new differential peak to peak measurement approach to reduce the ac voltage measurement error. The method holds the average peak amplitude of each polarity. Ultralow offset difference amplifier is used to measure peak to peak voltage. The method is insensitive to the variations in the dc offset of the source. The functionality of this method has been tested and compared with the conventional rf voltage measurement method. The output of this proposed technique is dc, which can be measured with an error of less than 0.1%.

Measurement of total ultrasonic power using thermal expansion and change in buoyancy of an absorbing target.

The Radiation Force Balance (RFB) technique is well established and most widely used for the measurement of total ultrasonic power radiated by ultrasonic transducer. The technique is used as a primary standard for calibration of ultrasonic transducers with relatively fair uncertainty in the low power (below 1 W) regime. In this technique, uncertainty comparatively increases in the range of few watts wherein the effects such as thermal heating of the target, cavitations, and acoustic streaming dominate. In addition, error in the measurement of ultrasonic power is also caused due to movement of absorber at relatively high radiated force which occurs at high power level. In this article a new technique is proposed which does not measure the balance output during transducer energized state as done in RFB. It utilizes the change in buoyancy of the absorbing target due to local thermal heating. The linear thermal expansion of the target changes the apparent mass in water due to buoyancy change. This forms the basis for the measurement of ultrasonic power particularly in watts range. The proposed method comparatively reduces uncertainty caused by various ultrasonic effects that occur at high power such as overshoot due to momentum of target at higher radiated force. The functionality of the technique has been tested and compared with the existing internationally recommended RFB technique.

ON THE MEASUREMENT OF LONGITUDINAL AND SHEAR ULTRASONIC VELOCITIES

Ultrasonic longitudinal and shear wave velocities can be evaluated in cylindrical specimens using line contact with transducers. The present communication discusses various important aspects involved in the method regarding time of arrival, phase and height of the echoes.

Physical Properties Of Eu3Ba2Mn2Cu2O12

The physical properties of the manganocuprate compound, Eu3Ba2Mn2Cu2O12 (Eu‐3222) are investigated using X‐ray diffraction, resistivity, magnetization and dielectric measurements. The structure of the Eu‐3222 compound is made by the intermixing of Eu‐123 (oxygen deficient triple perovskite block) and Eu‐214 (K2NiF4 type single rock‐salt like block). Electrical resistivity data show insulating behavior down to the measurable temperature and exhibits a conduction mechanism which can be explained on the basis of 3D variable range hopping model. Magnetization data shows a antiferromagnetic behavior at 5 K, however without any clear signature of magnetic ordering in the temperature range 5–300 K. Dielectric (Capacitance), measured as a function of temperature at various frequencies exhibits frequency dependence, indicating glassy relaxation of dipole moments.