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

We present a wearable passive UHF RFID tag based on a circularly polarized (CP) patch antenna on a textile substrate The antenna miniaturization is based on applying a combination of the cross- and L-shaped slots in the radiator In conjunction, the right-hand circular polarization is achieved by asymmetrically truncating all four corners of the square-shaped radiator Despite using a regular low-permittivity textile as the antenna substrate, we downsized the antenna to a 5 cm $\times \,\,5$ cm footprint with the thickness of 4 mm, which is equal to $01525 {\lambda }\,\, \times \,\,01525 {\lambda }\,\, \times \,\,00091 {\lambda }$ , where $ {\lambda }$ is the free space wavelength at 915 MHz In the numerical modeling and optimization of the antenna, we used a simplified cuboid-shaped and anatomical human body models In addition to simulated conventional antenna performance indicators, we introduce spatial coverage as a new parameter for assessing the detection reliability of UHF RFID tags Finally, we measured a manufactured tag worn in four different configurations on the body The measured axial ratio value was approximately 2 dB in all cases and the tag provided a high attainable read range of around 58 meters for a right-hand CP reader emitting 328 W EIRP

A Small All-Corners-Truncated Circularly Polarized Microstrip Patch Antenna on Textile Substrate for Wearable Passive UHF RFID Tags

This paper presents the backscattering properties and power delivery between reader and tag of three UHF RFID tags with two different IC-chips were studied in a reflective metallic Faraday gage environment by measuring threshold power, backscattered signal power and RCS. The results establish that highly reflective environment caused significant variations in threshold power levels and increase in the power level of the reader's signal the may impair the backscattering properties of the tag rather than give more reliable response. This suggests that in applications where one needs to identify objects in reflective environments adaptive power adjustment in the reader unit may give better results.

Performance of a passive UHF RFID tag in reflective environment

Backscattering-based RFID-inspired communication provides an effective approach for wireless power and data transfer for implantable battery-free brain machine interface microsystems. We compare conventional and segmented transmit loop configurations to reduce the specific absorption rate (SAR) into human body. Moreover, we present novel cubic-millimeter implant antennas and link performance comparisons in terms of both power and voltage delivery to the implant.

Antenna design for implanted tags in wireless brain machine interface system

We present the simulation-based design of UHF RFID tags based on electro-textile antennas and analyze the impact of recurrent washing on their performance through measurements. The antennas were fabricated from silver plated stretchable fabric made of nylon and elastic fibers. We coated half of the tested samples with acrylic spray to compare the influence of recurrent washing on the performance of the coated and uncoated tags. The fully functional tags including the microchip were washed ten times in a household washing machine using a typical 40°C program and detergent. The performance of the tags was measured after each wash. Prior washing, the peak read ranges of the tags were over 5.5 m. After ten washing cycles, the read ranges of coated and non-coated tags were 1.5 m and 2.8 m, respectively.

Impact of recurrent washing on the performance of electro-textile UHF RFID tags

In this study, the on-body read range performance of a wearable ultra-high frequency (UHF) radio frequency identification (RFID) tag is evaluated. The tag is fabricated using conductive thread and an embroidery machine. A measurement scenario is described, in which such an embroidered tag is attached to human clothing. The measurement results demonstrate the practical read ranges of the tag utilizing the new concept of using conductive threads. A maximum read range of 1.30 meters is attained.

Toni Bjorninen

Papers

A Small All-Corners-Truncated Circularly Polarized Microstrip Patch Antenna on Textile Substrate for Wearable Passive UHF RFID Tags

Performance of a passive UHF RFID tag in reflective environment

Antenna design for implanted tags in wireless brain machine interface system

Impact of recurrent washing on the performance of electro-textile UHF RFID tags

Practical read range evaluation of wearable embroidered UHF RFID tag