Elfed Lewis

A comparative review of wireless sensor network mote technologies

In the past 10 years, wireless sensor networks have grown from a theoretical concept to a burgeoning modern technology. In this paper, we present a comparative review of several wireless sensor network motes. We analyze these WSN devices under a number of different parameters and criteria, including processing ability, expected lifetime and measurement capabilities. We compare and contrast the selected WSN motes under these different headings, highlighting the individual motes performance under each category

A novel technique for optical fiber pH sensing based on methylene blue adsorption

A novel fiber optic pH sensor is reported. The sensor is based upon surfacic adsorption of methylene blue dye, producing absorption in the evanescent field surrounding the sensing fiber. The sensor is based upon a 200 /spl mu/m diameter Plastic Clad Silica (PCS) fiber which has its cladding removed in order to expose its core. The linear range of operation is between pH 3 and pH 9 and its response time is considerably shorter than indicator based probes which measure spectral changes of pH sensitive chemicals. Effects of measurand ionic strength are shown to be negligible which is a further important advantage of this sensor over other optical fiber pH sensors. The sensor design is sufficiently flexible to allow it to be configured in probe (reflective) or in-line (transmissive) form. The latter allows the application of time domain reflectometry technique which may be used to achieve multipoint (distributed) sensing. >

Wireless Sensor Node hardware: A review

Wireless sensor networks (WSN) are becoming increasingly popular, due to the benefits they bring to many applications as well as the increasing availability and maturity of the underlying technology. The fundamental building blocks of these networks are the sensor nodes themselves, the sensors attached to these nodes, and the software running on the nodes. A basic sensor node platform consists of a CPU, a radio and a power supply. For the last 10 years a number of research institutions and companies have been designing and producing nodes with these three components as a minimum. We review how these sensor nodes have evolved over this time and we also categorize the features of various platforms so as to enable an application developer to quickly determine which node is appropriate for their particular network or which features are desirable for inclusion on a custom built sensor platform.

Security for wireless sensor networks: A review

Due to the sensitive nature of the data gathered by many wireless sensor networks (WSNs) it is becoming critical that this data be protected. However, due to the constrained nature of the resources available on sensor nodes, traditional wireless networking security solutions are not viable due to their processing requirements, power consumption, speed and communications overhead. We review the threats and attacks faced by WSNs and then the current state of the art of dedicated WSN security protocols are examined and compared, focusing on their relative strengths and weaknesses.

A review of recent advances in optical fibre sensors for in vivo dosimetry during radiotherapy.

This article presents an overview of the recent developments and requirements in radiotherapy dosimetry, with particular emphasis on the development of optical fibre dosemeters for radiotherapy applications, focusing particularly on in vivo applications. Optical fibres offer considerable advantages over conventional techniques for radiotherapy dosimetry, owing to their small size, immunity to electromagnetic interferences, and suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based dosemeters, together with being lightweight and flexible, mean that they are minimally invasive and thus particularly suited to in vivo dosimetry. This means that the sensor can be placed directly inside a patient, for example, for brachytherapy treatments, the optical fibres could be placed in the tumour itself or into nearby critical tissues requiring monitoring, via the same applicators or needles used for the treatment delivery thereby providing real-time dosimetric information. The article outlines the principal sensor design systems along with some of the main strengths and weaknesses associated with the development of these techniques. The successful demonstration of these sensors in a range of different clinical environments is also presented.

Efficiently securing data on a wireless sensor network

Due to the sensitive nature of the data many wireless sensor networks are tasked to collect security of this data is an important concern. The best way to secure this data is to encrypt it using a secure encryption algorithm before it is transmitted over the air ways. However due to the constrained nature of the resources available on sensor nodes the cost, both in terms of power consumption and speed, of any software based encryption procedure can often out weigh the risks of the transmission being intercepted. We present a solution to reduce this cost of employing encryption by taking advantage of a resource already available on many sensor nodes; this resource being the encryption module available on the Chipcon CC2420 transceiver chip.

Fiber optic sensors for temperature monitoring during thermal treatments: An overview

During recent decades, minimally invasive thermal treatments (i.e., Radiofrequency ablation, Laser ablation, Microwave ablation, High Intensity Focused Ultrasound ablation, and Cryo-ablation) have gained widespread recognition in the field of tumor removal. These techniques induce a localized temperature increase or decrease to remove the tumor while the surrounding healthy tissue remains intact. An accurate measurement of tissue temperature may be particularly beneficial to improve treatment outcomes, because it can be used as a clear end-point to achieve complete tumor ablation and minimize recurrence. Among the several thermometric techniques used in this field, fiber optic sensors (FOSs) have several attractive features: high flexibility and small size of both sensor and cabling, allowing insertion of FOSs within deep-seated tissue; metrological characteristics, such as accuracy (better than 1 °C), sensitivity (e.g., 10 pm·°C−1 for Fiber Bragg Gratings), and frequency response (hundreds of kHz), are adequate for this application; immunity to electromagnetic interference allows the use of FOSs during Magnetic Resonance- or Computed Tomography-guided thermal procedures. In this review the current status of the most used FOSs for temperature monitoring during thermal procedure (e.g., fiber Bragg Grating sensors; fluoroptic sensors) is presented, with emphasis placed on their working principles and metrological characteristics. The essential physics of the common ablation techniques are included to explain the advantages of using FOSs during these procedures.

Fiber-optic chirped FBG for distributed thermal monitoring of ex-vivo radiofrequency ablation of liver

A linearly chirped fiber Bragg grating (LCFBG) has been used as a temperature sensor for online monitoring of radiofrequency thermal ablation (RFTA). The LCFBG acts as a distributed sensor, with spatial resolution of 75 μm. A white-light setup that records the LCFBG spectrum estimates the temperature profile in real time. Three RFTA experiments have been performed ex-vivo on porcine liver measuring the radial temperature distribution during the heating process. The analysis of thermal maps quantifies the spatial heat distribution along the measurement axis and determines the ablation efficiency.

Neural networks and pattern recognition techniques applied to optical fibre sensors

Some of the significant recent advances in the field of artificial neural networks (ANNs) applied to optical fibre sensors are reviewed. Particular attention is given to the use of ANNs in the enhancement of the performance of existing single point sensors, two- and three-dimensional measurements and developments in multipoint sensors and sensor arrays.

Optical Fibre Pressure Sensors in Medical Applications

This article is focused on reviewing the current state-of-the-art of optical fibre pressure sensors for medical applications. Optical fibres have inherent advantages due to their small size, immunity to electromagnetic interferences and their suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based pressure sensors, together with being lightweight and flexible, mean that they are minimally invasive for many medical applications and, thus, particularly suited to in vivo measurement. This means that the sensor can be placed directly inside a patient, e.g., for urodynamic and cardiovascular assessment. This paper presents an overview of the recent developments in optical fibre-based pressure measurements with particular reference to these application areas.