12,694 research outputs found
Trans-impedance amplifier of source follower topology using an active device for bandwidth extension in optical communication systems
No full textThis paper presents a trans-impedance amplifier (TLA) of a source follower topology for bandwidth extension. An analytical model for designing a TIA with a source follower stage has been derived. Based on this approach, we have designed two TIAs, which are a conventional common source TIA (CS-TIA) and a proposed source follower TIA (SF-TIA) for bandwidth extension. They were implemented for a 2.5-Gbps optical receiver using commercial 0.5 mum metal semiconductor field-effect transistor (MESFET) technologies. The trans-impedance gain (TIG) of the two fabricated amplifiers is the same, at 59 dBOmega. The measured bandwidth of the CS-TIA is 2.35 GHz, and that of the proposed SF-TIA is 4.05 GHz, enhanced by 1.7 GHz
Three-axis lever actuator with flexure hinges for an optical disk system
No full textA three-axis lever actuator with a flexure hinge has been designed and fabricated. This actuator is driven by electromagnetic force based on a coil-magnet system and can be used as a high precision actuator and, especially as a pickup head actuator in optical disks. High precision and low sensitivity to external vibration are the major advantages of this lever actuator. An analysis model was found and compared to the finite element method. Dynamic characteristics of the three-axis lever actuator were measured. The results are in very close agreement to those predicted by the model and finite element analysis. (C) 2002 American Institute of Physics
Development of FBG sensor system for measuring the high-frequency vibration of structures and the natural frequency
No full text
Performance analysis of partial erasure decoding with adaptive erasure-decision for RS coded FH/SSMA communications
No full textIn this paper, we propose a partial erasure decoding scheme with erasure-decision threshold for Reed-Solonlon (RS) codes and analyze its performance in frequency-hopped multiple-access communications. RS code is used to correct erasures and errors caused by other-user interference. Binary FSK is employed to transmit the channel symbol. The proposed decoder decides whether to erase the received RS code symbol based on the ersure decsion threshold. The approximated formula for optimal erasure decision threshold is derived in such a way that packet error probability can be minimized. Numerical results show that the employment of adaptive erasure decision threshold attains the higher normalized throughput in the areas of high channel traffic cases
EFFECT OF A/B VOLUME FRACTION ON THE SUPERPLASTIC DEFORMATION BEHAVIOR OF TI-6AL-4V ALLOY
No full textDamage to brittle coating layer with compliant substrate from concentrated loads
No full textThe mechanics of contact-induced damage in brittle layers on soft support substrates are of interest for their relevance to lifetime-limiting failures of technological laminate systems in concentrated loading. The results of experiments model bilayer that enable in situ viewing during loading with simple concentrated loads (spherical indenters) and yet simulate the essential features of damage in a wide range of engineering layer structures are described. The experiments reveal a competition between damage modes-cone cracks at the top (near-contact) brittle-layer surfaces and laterally-extending radial cracks at the lower surfaces. Hertzian loading superposed tangential loads shows slight shift of critical load point and value and it represents that tangential loads are secondary issue. The effect of slow crack growth is demonstrated in brittle coating on supporting substrate. The critical loads for radial crack depend sensitively on adhesive thickness and modulus. Delamination at the interface in poorly bonded specimens greatly reduces the critical loads of radial cracking
In situ runout identification in active magnetic bearing system by extended influence coefficient method
No full textIn this paper, an efficient, Set easy-to-use, in-situ runout identification scheme, based on the extended influence coefficient method, is presented for active magnetic bearing (AMB) systems, It is shown experimentally that the proposed scheme successfully identifies and eliminates the troublesome runout of a well-balanced AMB system in the laboratory, so that a high-precision spindle system can be achieved, while it is in operation
Prediction of differential drying shrinkage in concrete
No full textThe non-uniform moisture distribution in concrete causes the differential drying shrinkage. From this type of differential drying shrinkage, tensile stress occurs on the exposed surface of concrete structures and may result in crack formation. This residual stress is significantly affected by the creep of concrete. In this study, for the purpose of predicting the differential drying shrinkage, the analysis method was suggested, in which the creep of concrete was also considered. In addition, the differential drying shrinkage strain was measured at various positions in concrete by using embedded strain gauges. The internal drying shrinkage strain differs significantly according to the depth from exposed surface. The validity of analysis method was verified by comparing test results with analytical results. Finally it was found that analytical results were in good agreement with test results. (C) 1998 Elsevier Science Ltd
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