WITH the ever-widening scope of modern mathematical analysis and its many ramifications, it is quite impossible to include, in a single volume of reasonable size, an adequate and exhaustive discussion of the calculus in its more advanced stages. It therefore becomes necessary, in planning a thoroughly sound course in the subject, to consider several important aspects of the vast field confronting a modern writer. The limitation of space renders the selection of subject-matter fundamentally dependent upon the aim of the course, which may or may not be related to the content of specific examination syllabuses. Logical development, too, may lead to the inclusion of many topics which, at present, may only be of academic interest, while others, of greater practical value, may have to be omitted. The experience and training of the writer may also have, more or less, a bearing on both these considerations.Advanced CalculusBy Dr. C. A. Stewart. Pp. xviii + 523. (London: Methuen and Co., Ltd., 1940.) 25s.

Advanced Calculus I

Antenna Theory And Design

A strain sensor has been fabricated from a polymer nanocomposite with multiwalled carbon nanotube (MWNT) fillers. The piezoresistivity
of this nanocomposite strain sensor has been investigated based on an improved three-dimensional (3D) statistical resistor network
model incorporating the tunneling effect between the neighboring carbon nanotubes (CNTs), and a fiber reorientation model. The
numerical results agree very well with the experimental measurements. As compared with traditional strain gauges, much higher sensitivity
can be obtained in the nanocomposite sensors when the volume fraction of CNT is close to the percolation threshold. For a small
CNT volume fraction, weak nonlinear piezoresistivity is observed both experimentally and from numerical simulation. The tunneling
effect is considered to be the principal mechanism of the sensor under small strains.

Tunneling effect in a polymer/carbon nanotube nanocompositestrain sensor

Post-transition elements, together with zinc-group metals and their alloys belong to an emerging class of materials with fascinating characteristics originating from their simultaneous metallic and liquid natures. These metals and alloys are characterised by having low melting points (i.e. between room temperature and 300 °C), making their liquid state accessible to practical applications in various fields of physical chemistry and synthesis. These materials can offer extraordinary capabilities in the synthesis of new materials, catalysis and can also enable novel applications including microfluidics, flexible electronics and drug delivery. However, surprisingly liquid metals have been somewhat neglected by the wider research community. In this review, we provide a comprehensive overview of the fundamentals underlying liquid metal research, including liquid metal synthesis, surface functionalisation and liquid metal enabled chemistry. Furthermore, we discuss phenomena that warrant further investigations in relevant fields and outline how liquid metals can contribute to exciting future applications.

Liquid metals: fundamentals and applications in chemistry

The current evolution of the traditional medical model toward the participatory medicine can be boosted by the Internet of Things (IoT) paradigm involving sensors (environmental, wearable, and implanted) spread inside domestic environments with the purpose to monitor the user’s health and activate remote assistance. RF identification (RFID) technology is now mature to provide part of the IoT physical layer for the personal healthcare in smart environments through low-cost, energy-autonomous, and disposable sensors. It is here presented a survey on the state-of-the-art of RFID for application to bodycentric systems and for gathering information (temperature, humidity, and other gases) about the user’s living environment. Many available options are described up to the application level with some examples of RFID systems able to collect and process multichannel data about the human behavior in compliance with the power exposure and sanitary regulations. Open challenges and possible new research trends are finally discussed.

RFID Technology for IoT-Based Personal Healthcare in Smart Spaces

Modified Wilkinson power divider with harmonics suppression and compact size for GSM applications

Additive deposition of inks with metallic inclusions provides compelling means to embed electronics into clothing in a seamless way. We present a simple single-step brush-painting method for depositing copper and silver inks directly on ordinary cotton fabric and discuss the optimization of the photonical sintering of both materials. For the first time, we demonstrate the deposition and sintering of copper oxide ink on fabric achieving high electrical conductivity suitable for radio-frequency electronics. The results from wireless testing confirmed that the radio-frequency identification tags based on the copper and silver ink antennas were readable from 6 and 10 m, respectively.

Brush-painting and photonical sintering of copper and silver inks on cotton fabric to form antennas for wearable ultra-high-frequency radio-frequency identification tags:

Inkjet-printing offers a potential alternative to conventional tags manufactured by etching. The inkjet-printed narrow-line tags discussed in this paper are fabricated using less conductive materials than conventional tags. This paper presents the performance of the narrow-line tags when used on different materials. We present read range comparison of passive ultra high frequency (UHF) inkjet-printed narrow-line radio frequency identification (RFID) tags in air and attached to diverse objects. We have also compared the results to a dipole-type commercial copper fabricated tag. Measurement results show that materials under identification affect narrow-line tag performance such as read range and operational frequency and bandwidth.

Performance of inkjet-printed narrow-line passive UHF RFID tags on different objects

We present a quasi-Yagi antenna mounted on a periodic surface for a wearable UHF RFID reader operating in the UHF RFID frequency band centered at 915 MHz. The periodic surface was co-optimized with the antenna to enhance the launching of surface waves to enable the end-fire radiation along the forearm so that a user can identify objects by pointing her/his hand towards them. In addition to the radiation pattern modification, the ground plane of the periodic surface serves the second purpose of isolating the antenna from the human body. We optimized the antenna in a full-wave EM simulator using a simplified cylindrical model of the forearm and in the simulation, it achieved the end-fire directivity of 5.9 dBi along the forearm. In the wireless testing, the quasi-Yagi antenna provided the read range of 3.8 m for a typical UHF RFID tag having 0 dBi gain when the reader’s output power was 32 dBm that corresponds with EIRP =0.56 W and SAR =0.191 W/kg in our simulations. Considering both, the RFID emission regulations with EIRP = 3.28 W or 4 W and the SAR limit of 1.6 W/kg averaged over 1 gram of tissue, the read range could be further enhanced for reader units with higher output power.

/pdf/wearable-metasurface-enabled-quasi-yagi-antenna-for-uhf-rfid-3qdaxf78or.pdf

Wearable Metasurface-Enabled Quasi-Yagi Antenna for UHF RFID Reader With End-Fire Radiation Along the Forearm

This communication presents a 3-D loop antenna to overcome the impact of small lateral misalignment of the order of 2 mm between the inductively coupled antennas. This communication is a continuation of our previously reported work. In our previous work, we have successfully activated the pressure monitoring sensor and performed the pressure readout for an intracranial pressure monitoring application. The pressure sensor was activated through wireless inductive near-field powering. Measurement showed that there was significant effect on pressure readout accuracy due to small lateral misalignment between the inductively coupled antennas. In this communication, we demonstrate that the structural properties of a simple 3-D loop antenna help to overcome the pressure readout error caused by small lateral misalignment. We present the design procedure, simulation results, and pressure readout measurement of the proposed 3-D loop antenna. Moreover, the pressure monitoring system shows maximum improvement of 9 mmHg in pressure readout accuracy with the proposed 3-D loop antenna.

Characterization of 3-D Loop Antenna to Overcome the Impact of Small Lateral Misalignment in Wirelessly Powered Intracranial Pressure Monitoring System

Toni Bjorninen

Papers

Modified Wilkinson power divider with harmonics suppression and compact size for GSM applications

Brush-painting and photonical sintering of copper and silver inks on cotton fabric to form antennas for wearable ultra-high-frequency radio-frequency identification tags:

Performance of inkjet-printed narrow-line passive UHF RFID tags on different objects

Wearable Metasurface-Enabled Quasi-Yagi Antenna for UHF RFID Reader With End-Fire Radiation Along the Forearm

Characterization of 3-D Loop Antenna to Overcome the Impact of Small Lateral Misalignment in Wirelessly Powered Intracranial Pressure Monitoring System