China
Africa
Explore chapters and articles related to this topic
Near-Surface Particle-Tracking Velocimetry
Published in Sushanta K. Mitra, Suman Chakraborty, Fabrication, Implementation, and Applications, 2016
Peter Huang, Jeffrey S. Guasto, Kenneth S. Breuer
An example of an objective TIRF microscope system is shown in Figure 3.14. An illumination beam produced by a laser is first regulated by a power attenuator-half-wave plate-polarizing beam splitter combination to achieve the desired power level. This step down in power is especially critical to high-power laser beams produced by pulsed lasers as their high-energy density can easily damage the optical components inside a microscope objective. A portion of the beam energy is diverted to an energy meter to monitor the laser stability. The beam is then “cleaned up” by a spatial filter (concave lens–10-µm pinholeconcave lens combination) before being directed through an NA1.45 100X oil-immersion microscope objective at an angle that creates evanescent waves inside a microchannel. Fluorescent images of near-surface tracer particles are captured by the same microscope objective and screened by a dichroic mirror and a barrier filter before being projected onto an intensified charge-coupled device (CCD) camera, capable of recording extremely low-intensity events. A TTL pulse generator is used to synchronize laser firing and intensified CCD image acquisitions to ensure precise control imaging timing. The energy of the illuminating laser beam can also be recorded simultaneously with each image acquisition to account for illuminating energy fluctuation, if necessary.
Power Amplifier Behavioral Model and Nonlinear Analysis Basis
Published in Jingchang Nan, Mingming Gao, Nonlinear Modeling Analysis and Predistortion Algorithm Research of Radio Frequency Power Amplifiers, 2021
X-parameter modeling [10] is a data-based modeling scheme, and therefore the extraction of X-parameters is a critical step in the X-parameter modeling process. There are basically two methods to extract X-parameters. One is to use the device, nonlinear vector network analyzer (NVNA), and the other is to use software, advanced design system (ADS). The device-based X-parameter extraction scheme requires a real test bench setup, including various additional accessories (PA, high-power directional coupler, high-power attenuator, etc.).
EMI Measurements, Control Requirements, and Test Methods
Published in David A. Weston, Electromagnetic Compatibility, 2017
Equipment ChecklistSignal generator 0.15–80 MHz with either an AM modulation capability of 1 kHz at 80% or an external modulation input.Signal generator for 1 kHz. If generator in (1) requires an external modulation source. If generator in (1) does not have an external modulation input, then a modulator is required between the signal generator output and the power amplifier in (3).Power amplifier 0.15–80 MHz. Typically 10–75 W, depending on injection method, with 50-ohm source impedance.Inductive injection clamp or coupling/decoupling networks (CDNs) or capacitor/resistor networks (see 6) for direct coupling.Ferrite ring cores for the direct coupling into screened (shielded) cables test set.100-ohm and 50-ohm series injection and load resistors and for direct coupling into nonscreened (unshielded) cables <20-nF coupling capacitors.Oscilloscope with at least a 100-MHz bandwidth and a 50-Ω input impedance or a 50-Ω terminating resistor.Spectrum analyzer or EMI receiver.>6-dB power attenuator. Required for CDN injection only.
Theoretical and experimental study on guided wave characteristics in bonded bolts
Published in Mechanics of Advanced Materials and Structures, 2023
Zhi Li, Jiangong Yu, Xiaoming Zhang, L. Elmaimouni
The work principle for testing system: The parameters of the required excitation signal are set by the ultrasonic testing system software on the computer. The required signal is generated by the ultrasonic test system and output after power amplification. The ultrasonic longitudinal wave straight probe is excited after the load high power, high power attenuator, diplexer pre-amplifier, and signal sampler to generate an ultrasonic guided wave with specific frequency in the bolt. The reflected echo is generated after the guided wave reaches the bottom of the bolt, and received by the same straight probe and displayed on the oscilloscope through the signal sampler, duplexer preamplifier and ultrasonic detection system. The test data can be saved directly by the USB port of the oscilloscope for signal analysis. Impedance is used to protect the ultrasonic testing system. When the output power of the system is too high, it can be attenuated by the attenuator. The diplexer pre-amplifier is used for self-sending and self-receiving of the straight probe at one end of the bolt. The signal sampler collects the transmitted signal and displays it on the oscilloscope. The straight probe is placed at the end of the sample and acted on the bolt through the coupling agent.