High-energy radiation-resistant vulcanizates. II. EPDM

In this article, Part II of the series, we report a detail study on stabilization of EPDM vulcanizates in γ-radiation environment. The special additives (antirads), namely pyrene (Py), brominated acenaphthene (BrAc), poly(acenaphthene sulfide) (PAcSu) and poly(pyrene sulfide) (PPySu) were used for the stabilization studies. The efficiency of these antirads for EPDM had been monitored by the means of electrical resistivity, wide-angle X-ray diffraction, and mechanical properties. The stabilization of EPDM to withstand 200 Mrads of γ radiation in air environment is achieved. © 1994 John Wiley & Sons, Inc.     

An electrochemical study on deformed galvanneal steel sheets

Corrosion behavior of deformed galvanneal steel sheets has been evaluated as a function of their degree of deformation under four different strain paths namely, biaxial, uniaxial (drawing), plane strain and tensile mode. A correlation between the degree of deformation and the loss in the extent of corrosion protection offered by these coatings in 3.5 wt.% NaCl solution has been established by carrying out electrochemical studies such as potentiodynamic polarization and electrochemical impedance spectroscopy. An almost linear relation has been found to exist between the effective strain applied to the specimen and damage caused to the coating. While uniaxial, plane strain and tensile modes of deformation have been found to affect the coating corrosion resistance almost to the same extent, the biaxial deformation has been found to cause a greater damage to the coating.     

Flux Tracking Methods for Direct Field Orientation

Numerous techniques have been reported in the literature to accomplish the task of locating the rotor flux axis for the purpose of direct field orientation. This paper first summarizes the existing sensorless techniques using high-frequency test signal injection to determine the flux spatial location in an induction machine. A novel approach employing balanced and unbalanced excitation is then investigated to track the flux. It is first demonstrated that the rotating flux vector in the machine causes saturation-induced saliency in the phases under normal operating conditions. By employing high-frequency test signals, this saliency is monitored and then used to track the flux in the machine under test. The feasibility of the proposed approach is verified with experimental results.     

Effects of device design on InP-based HBT thermalresistance

The thermal resistance of InP-based single and double heterojunction bipolar transistors has been measured. The double heterojunction bipolar transistor (DHBT) device employs an InP collector to improve thermal conductivity and reduce the base-emitter junction temperature rise. DHBTs were grown with heavily doped InGaAs or InP sub-collectors for low resistance contacts. As expected, the all-InP collector (sub-collector and collector) had the lowest thermal resistance while the all-InGaAs collector (sub-collector and collector) had the highest thermal resistance. For a device with emitter size of 1 × 3 μm², the room temperature thermal resistance of the all-InP collector DHBT was 3.9°C/mW. The DHBT with an InGaAs sub-collector had a thermal resistance of 5.6°C/mW, while the SHBT had a thermal resistance of 12.3°C/mW. Also compared were effects of device layout parameters on thermal resistance and the effect of the topside metal thickness. Devices with the largest perimeter-to-area ratio had the lowest thermal resistance when normalized to emitter area. HBTs with conservative alignment tolerances (L1) had similar thermal resistance to those with aggressive alignment tolerances (L2). The reduced parasitic capacitance of the L2-style SHBT improved the device f _T from 150 to 183 GHz at 6.0-mA collector current. Alternately, the reduced parasitics allowed the SHBT to operate at 150 GHz f_T at 2.9 mA, reducing the junction temperature rise by more than half. Doubling the topside metal thickness improved the thermal resistance by 31% at room temperature     

Concentric Ring Structured Reconfigurable Antenna using MEMS Switches for Wireless Communication Applications

Wireless Personal Communications - This paper proposes a reconfigurable circular microstrip antenna to serve the wireless communication applications that make use frequency bands such as ISM...