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 e-textile passive UHF RFID tag based on a split ring resonator antenna. The antenna was optimised using a full-wave electromagnetic solver and the prototyped tag was tested in wireless measurements. The detection range of the tag is 2.8 metres at 915 MHz when affixed to the upper back of a person on a textile substrate with the thickness of only two millimetres. In the wireless measurement, we found a close match with the simulations where a homogenous dielectric cuboid representing the torso of a person and studied the impact of nonoptimal antenna-body alignments and separations. Overall, the results indicate that the uniplanar split ring antenna achieves robust operation required in the practical wearable applications.

Wearable E-textile split ring passive UHF RFID tag: Body-worn performance evaluation

A compact slot type tag antenna design for passive UHF RFID is presented. Advantages of slot type radiators in UHF RFID are discussed. Physical operation principle of the proposed antenna structure is explained and explored by simulations. Modeling results at different design stages are presented and a case study of realization of impedance matching to a specific RFID IC is discussed. Design verification is done by wireless protocol-based measurements, results are presented and compared with our previous tag antenna designs.

Design and non-invasive design verification of a slot-type passive UHF RFID tag

We outline the development of an RF energy harvester manufactured on regular packaging cardboard using the inkjet-printing technology. The harvester is composed of a planar monopole antenna, impedance matching network and a voltage doubler circuit. The paper summarizes the procedure of achieving highly conductive traces on rough and porous cardboard, describes the circuit and antenna design, and presents simulated and measured results.

Inkjet-printed monopole antenna and voltage doubler on cardboard for RF energy harvesting

We present a spatially distributed split ring resonator (SRR) antenna system comprising a small implanted split ring resonator carrying a UHF RFID microsystem and a wearable split ring. In the wireless experiments, the backscatter response of the microsystem is detectable at a distance of 1 m within the entire UHF RFID band from 840 to 960 MHz when the implant depth is 10 mm or less. Moreover, its working distance remains higher than 90 cm under marked, up to 5 mm later or 30° rotational, misalignment between the implanted and wearable parts.

Split ring resonator antenna system with implantable and wearable parts for far field readable backscattering implants

This paper presents laboratory-scale methods for attaching integrated circuits (ICs) to passive ultra high frequency (UHF) radio frequency identification (RFID) antennas and discusses the effects of the attaching methods on tag performance. Commercial passive UHF RFID ICs were used. The studied attachment methods were strap attachment and direct IC attachment. One antenna design was developed for strap attachment where the IC was attached together with a strap, and two different antenna designs were developed for direct chip attachment. In addition, etched copper loop arm antennas for strap attachment and inkjet-printed loop arm antennas for direct chip attachment were studied. The measurement results show that the interconnection between the IC and the antenna is of paramount importance and that the performance of the tag is strongly dependent on the quality of the interconnection. The results of this study provide knowledge for reliable IC attachment in prototype laboratory conditions.

Toni Bjorninen

Papers

Wearable E-textile split ring passive UHF RFID tag: Body-worn performance evaluation

Design and non-invasive design verification of a slot-type passive UHF RFID tag

Inkjet-printed monopole antenna and voltage doubler on cardboard for RF energy harvesting

Split ring resonator antenna system with implantable and wearable parts for far field readable backscattering implants

Effects of laboratory-scale IC attachment methods on passive UHF RFID tag performance