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

This paper presents a loop antenna for deep implant powering in an intracranial pressure (ICP) monitoring application. This work is continuation of our on-going development of a wirelessly powered implantable system for ICP monitoring. Experimental results indicate that the implant can be activated until the depth of 19 mm from the skin. This is 8 mm more than our previous work where we were able to activate the implant until 11 mm depth from the skin. Moreover, we have also presented pressure readout experimental results with the proposed antenna.

Loop Antenna for Deep Implant Powering in an Intracranial Pressure Monitoring System

In this paper we study the effect of magnetic core in both the implant and the external reader antenna and higher operational frequency of the implant for wireless passive Intracranial Pressure Monitoring (ICP). Implant and external reader antenna are inductively coupled. ICP can be monitored through the change of implant resonance frequency or external reader antenna input impedance phase dip. We demonstrate that improvement in the sensitivity of ICP monitoring through change of implant resonance frequency can be done by resonating implant at higher frequency. Moreover we perform measurement in biological environment by placing pig skin of 5 mm ± 1 mm between implant and external reader antenna.

Effect of magnetic core and higher operational frequency on sensitivity in frequency shift detection in wireless passive minimally invasive Intracranial Pressure Monitoring

The major challenge in developing a wireless brain implant is to establish a stable and efficient trans‐cranial wireless link with an integrated implantable antenna. This chapter discusses the challenges in developing the intracranial implantable antennas and compares different techniques for wireless power transfer in the presence of human body tissues. It provides a summary of the most recent miniature implantable antennas and inductive power transfer systems for implantable applications. Next, the chapter compares the merits of different methodologies to build the computational head models for implantable antenna development. A comparison of the human head models with different complexity is provided. Then, the chapter discusses the development and the performance of a wirelessly powered intracranial pressure sensing system integrating near‐ and far‐field antennas in the human head environment. Two far‐field radio‐frequency identification antennas for intracranial wireless communication are demonstrated and evaluated. Finally, the chapter discusses the antenna performance and the tuning parameters through a parametric analysis.

Antennas and Wireless Power Transfer for Brain-Implantable Sensors

We characterize textile antennas and antenna-electronics interconnections created by depositing conductive paint and by embroidering with conductive yarn. Both approaches are based on affordable materials and enable single-step manufacturing of RFID tag on textiles. To achieve further material savings, our dipole antennas comprise of line-type structures instead of the commonly used metallized surfaces. To understand the electromagnetic properties of the antennas and to assess the quality of the conductors, both wireless measurements and electromagnetic field simulations were used. Overall, the tags made of the conductive yarn by embroidering were detectable at the distances of 5-to-6 meters in air and at 2 meters on the human body. Conductive paint yielded the corresponding distances of 3.5-to-4 meters and 1 meter, respectively.

Antennas and antenna-electronics interfaces made of conductive yarn and paint for cost-effective wearable RFIDs and sensors

Wireless body-centric sensing systems require light-weight and wearable sensor nodes for remote health monitoring of people. This imposes the need for wearable antennas which are comfortable to the users. In this article we demonstrate the capability of conductive fabrics and embroidered structures in the fabrication of such antennas and sensors. We also outline their measured performance in several prominent applications.

Toni Bjorninen

Papers

Loop Antenna for Deep Implant Powering in an Intracranial Pressure Monitoring System

Effect of magnetic core and higher operational frequency on sensitivity in frequency shift detection in wireless passive minimally invasive Intracranial Pressure Monitoring

Antennas and Wireless Power Transfer for Brain-Implantable Sensors

Antennas and antenna-electronics interfaces made of conductive yarn and paint for cost-effective wearable RFIDs and sensors

Electro-textiles — The enabling technology for wearable antennas in wireless body-centric systems