We present the design of a planar, low‐profile dual‐band implantable antenna which operates in the 402‐ to 405‐MHz Medical Implant Communication Service (MICS) and the 2.4‐ to 2.5‐GHz Industrial, Scientific, and Medical (ISM) bands. The designed antenna was experimentally validated by implanting it first into a synthetic human skin tissue phantom and then a minced pork model. The measurement results show that the antenna has 10‐dB impedance bandwidths of at least 120 MHz which covers the MICS band and at least 40 MHz which covers the ISM band. The proposed antenna is printed on an RO3210 substrate and it occupies a compact volume of 22 mm × 16 mm × 1.27 mm. The average SAR values at the center frequency of both bands, that is, 403.5 MHz and 2.45 GHz are, respectively, below 0.352 and 0.054 μW/kg. Both values are far below the limits stipulated by the IEEE C95.1‐1999 (ie, 1.6 W/kg) and IEEE C95.1‐2005 (ie, 2 W/kg) standards. The simulated and measured performance of the antenna confirms its good radiation characteristics.

Activated sludge system is generally used in wastewater treatment plants for processing domestic influent. Conventionally the activated sludge wastewater treatment is monitored by measuring physico-chemical parameters like total suspended solids (TSSol), sludge volume index (SVI) and chemical oxygen demand (COD) etc. For the measurement, tests are conducted in the laboratory, which take many hours to give the final measurement. Digital image processing and analysis offers a better alternative not only to monitor and characterize the current state of activated sludge but also to predict the future state. The characterization by image processing and analysis is done by correlating the time evolution of parameters extracted by image analysis of floc and filaments with the physico-chemical parameters. This chapter briefly reviews the activated sludge wastewater treatment; and, procedures of image acquisition, preprocessing, segmentation and analysis in the specific context of activated sludge wastewater treatment. In the latter part additional procedures like z-stacking, image stitching are introduced for wastewater image preprocessing, which are not previously used in the context of activated sludge. Different preprocessing and segmentation techniques are proposed, along with the survey of imaging procedures reported in the literature. Finally the image analysis based morphological parameters and correlation of the parameters with regard to monitoring and prediction of activated sludge are discussed. Hence it is observed that image analysis can play a very useful role in the monitoring of activated sludge wastewater treatment plants.

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We present the design of a novel compact coplanar waveguide‐fed antenna with fractal s‐shaped patches for multiband applications. The antenna consists of three fractal s‐shaped patches with different lengths. We demonstrate that the number of resonant frequencies is in direct proportion with the number of fractal s‐shaped patches. This is to say that, the number of resonant frequencies in a multiband antenna can be increased by increasing the number of patches. The resonant frequencies can be selected by carefully adjusting the length of the patches. We have designed our antenna to operate at 2.5/5.3/7.1/8.4 GHz. The measurement results show that the proposed antenna has 10 dB impedance bandwidths of 622 MHz (2.322–2.944 GHz), 466 MHz (5.113–5.579 GHz), 121 MHz (6.890–7.011 GHz) and 1080 MHz (8.206–9.286 GHz) to cover all the 2.4 GHz Bluetooth, 5.5 GHz WiMAX, and 2.4/5.2 GHz WLAN bands. The latter two bands of our proposed antenna fall within the X band range which finds vast applications in radar, aircraft, spacecraft and mobile or satellite communication system. The proposed antenna is printed on a single‐layered FR4 substrate, and it occupies a small volume of 17 × 18 × 1.6 mm3. The simulated and measured performance of the antenna confirms its omnidirectional radiation pattern and quad‐band operation. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:541–546, 2017

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We present an analysis on the performance of the Cassegrain and Gregorian on-axis, off-axis and offset antennas. In our study, we have adopted the design parameters for the Cassegrain configuration used in the Atacama Large Millimeter Array (ALMA) project. Modifications on the original parameters are made so as to meet the design requirement for the off-axis and offset configurations. To reduce spillover loss in the offset antennas, we have adjusted the angle between the axis of the primary reflector and that of the sub-reflector, so that the feed horn is placed right next to the edge of the primary reflector. This is to allow the offset antennas to receive the highest power at the feed horn. The results obtained from the physical optics simulation show that the radiation characteristics of both Cassegrain and Gregorian antennas are similar. The offset designs exhibit the best performance, followed by the on-axis, and, finally, the off-axis designs. Our analysis also shows that the performance of both offset Cassegrain and Gregorian antennas are comparable to each other.

We present an accurate analysis on the attenuation of waves, propagating in rectangular waveguides with superconducting walls. The wavenumbers k x and k y in the x and y directions, respectively, are first obtained as roots of a set of transcendental equations developed by matching the tangential fields at the surface of the wall with the electrical properties of the wall material. The complex conductivity of the superconducting waveguide is obtained from the extended Mattis-Bardeen theory. The propagation constant k z is found by substituting the values of k x and k y into the dispersion relation. We have computed and compared the loss in the waveguides below and above the critical temperature. At frequencies above the cutoff frequency f c but below the gap frequency f g , the loss in the superconducting waveguide is significantly lower than that in a normal conducting waveguide. Above the gap frequency, however, the result indicates that the attenuation in the waveguide below the critical temperature is higher than that at room temperature. We attribute the higher loss as due to the higher surface resistance and field penetration for superconducting waveguides operating above the gap frequency.