Sensors

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Open AccessEditorial

Sensors Best Paper Award 2011

by Ophelia Han

Sensors 2011, 11(1), 1243-1245; https://doi.org/10.3390/s110101243 - 25 Jan 2011

Cited by 4 | Viewed by 7654

With the start of 2011, Sensors is instituting an annual award to recognize outstanding papers related to sensing technologies and applications that meet the aims, scope and high standards of this journal. We are pleased to announce the first “Sensors Best Paper [...] Read more.

With the start of 2011, Sensors is instituting an annual award to recognize outstanding papers related to sensing technologies and applications that meet the aims, scope and high standards of this journal. We are pleased to announce the first “Sensors Best Paper Award” for 2011. Nominations were solicited from the Section Editor-in-Chiefs of Sensors, with all papers published in 2005 eligible for consideration. [...] Full article

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1112 KiB

Open AccessArticle

Intelligent Sensing in Dynamic Environments Using Markov Decision Process

by Thrishantha Nanayakkara, Malka N. Halgamuge, Prasanna Sridhar and Asad M. Madni

Sensors 2011, 11(1), 1229-1242; https://doi.org/10.3390/s110101229 - 20 Jan 2011

Cited by 10 | Viewed by 8876

Abstract

In a network of low-powered wireless sensors, it is essential to capture as many environmental events as possible while still preserving the battery life of the sensor node. This paper focuses on a real-time learning algorithm to extend the lifetime of a sensor [...] Read more.

In a network of low-powered wireless sensors, it is essential to capture as many environmental events as possible while still preserving the battery life of the sensor node. This paper focuses on a real-time learning algorithm to extend the lifetime of a sensor node to sense and transmit environmental events. A common method that is generally adopted in ad-hoc sensor networks is to periodically put the sensor nodes to sleep. The purpose of the learning algorithm is to couple the sensor’s sleeping behavior to the natural statistics of the environment hence that it can be in optimal harmony with changes in the environment, the sensors can sleep when steady environment and stay awake when turbulent environment. This paper presents theoretical and experimental validation of a reward based learning algorithm that can be implemented on an embedded sensor. The key contribution of the proposed approach is the design and implementation of a reward function that satisfies a trade-off between the above two mutually contradicting objectives, and a linear critic function to approximate the discounted sum of future rewards in order to perform policy learning. Full article

(This article belongs to the Section Physical Sensors)

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564 KiB

Open AccessArticle

A New Tissue Resonator Indenter Device and Reliability Study

by Ming Jia, Jean W. Zu and Alireza Hariri

Sensors 2011, 11(1), 1212-1228; https://doi.org/10.3390/s110101212 - 20 Jan 2011

Cited by 11 | Viewed by 8452

Abstract

Knowledge of tissue mechanical properties is widely required by medical applications, such as disease diagnostics, surgery operation, simulation, planning, and training. A new portable device, called Tissue Resonator Indenter Device (TRID), has been developed for measurement of regional viscoelastic properties of soft tissues [...] Read more.

Knowledge of tissue mechanical properties is widely required by medical applications, such as disease diagnostics, surgery operation, simulation, planning, and training. A new portable device, called Tissue Resonator Indenter Device (TRID), has been developed for measurement of regional viscoelastic properties of soft tissues at the Bio-instrument and Biomechanics Lab of the University of Toronto. As a device for soft tissue properties in-vivo measurements, the reliability of TRID is crucial. This paper presents TRID’s working principle and the experimental study of TRID’s reliability with respect to inter-reliability, intra-reliability, and the indenter misalignment effect as well. Full article

(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)

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1042 KiB

Open AccessArticle

Developing a New Wireless Sensor Network Platform and Its Application in Precision Agriculture

by Raúl Aquino-Santos, Apolinar González-Potes, Arthur Edwards-Block and Raúl Alejandro Virgen-Ortiz

Sensors 2011, 11(1), 1192-1211; https://doi.org/10.3390/s110101192 - 20 Jan 2011

Cited by 46 | Viewed by 13660

Abstract

Wireless sensor networks are gaining greater attention from the research community and industrial professionals because these small pieces of “smart dust” offer great advantages due to their small size, low power consumption, easy integration and support for “green” applications. Green applications are considered [...] Read more.

Wireless sensor networks are gaining greater attention from the research community and industrial professionals because these small pieces of “smart dust” offer great advantages due to their small size, low power consumption, easy integration and support for “green” applications. Green applications are considered a hot topic in intelligent environments, ubiquitous and pervasive computing. This work evaluates a new wireless sensor network platform and its application in precision agriculture, including its embedded operating system and its routing algorithm. To validate the technological platform and the embedded operating system, two different routing strategies were compared: hierarchical and flat. Both of these routing algorithms were tested in a small-scale network applied to a watermelon field. However, we strongly believe that this technological platform can be also applied to precision agriculture because it incorporates a modified version of LORA-CBF, a wireless location-based routing algorithm that uses cluster-based flooding. Cluster-based flooding addresses the scalability concerns of wireless sensor networks, while the modified LORA-CBF routing algorithm includes a metric to monitor residual battery energy. Furthermore, results show that the modified version of LORA-CBF functions well with both the flat and hierarchical algorithms, although it functions better with the flat algorithm in a small-scale agricultural network. Full article

(This article belongs to the Special Issue Sensors in Agriculture and Forestry)

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650 KiB

Open AccessArticle

Respiratory Monitoring by Porphyrin Modified Quartz Crystal Microbalance Sensors

by Roman Selyanchyn, Serhiy Korposh, Shunichi Wakamatsu and Seung-Woo Lee

Sensors 2011, 11(1), 1177-1191; https://doi.org/10.3390/s110101177 - 20 Jan 2011

Cited by 19 | Viewed by 10761

Abstract

A respiratory monitoring system based on a quartz crystal microbalance (QCM) sensor with a functional film was designed and investigated. Porphyrins 5,10,15,20-tetrakis-(4-sulfophenyl)-21H,23H-porphine (TSPP) and 5,10,15,20-tetrakis-(4-sulfophenyl)-21H, 23H-porphine manganese (III) chloride (MnTSPP) used as sensitive elements were assembled with a poly(diallyldimethyl ammonium chloride) (PDDA). Films [...] Read more.

A respiratory monitoring system based on a quartz crystal microbalance (QCM) sensor with a functional film was designed and investigated. Porphyrins 5,10,15,20-tetrakis-(4-sulfophenyl)-21H,23H-porphine (TSPP) and 5,10,15,20-tetrakis-(4-sulfophenyl)-21H, 23H-porphine manganese (III) chloride (MnTSPP) used as sensitive elements were assembled with a poly(diallyldimethyl ammonium chloride) (PDDA). Films were deposited on the QCM resonators using layer-by-layer method in order to develop the sensor. The developed system, in which the sensor response reflects lung movements, was able to track human respiration providing respiratory rate (RR) and respiratory pattern (RP). The sensor system was tested on healthy volunteers to compare RPs and calculate RRs. The operation principle of the proposed system is based on the fast adsorption/desorption behavior of water originated from human breath into the sensor films deposited on the QCM electrode. Full article

(This article belongs to the Section Chemical Sensors)

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346 KiB

Open AccessReview

Advances in Electronic-Nose Technologies Developed for Biomedical Applications

by Alphus D. Wilson and Manuela Baietto

Sensors 2011, 11(1), 1105-1176; https://doi.org/10.3390/s110101105 - 19 Jan 2011

Cited by 308 | Viewed by 39131

Abstract

The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The [...] Read more.

The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry. Full article

(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)

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Open AccessArticle

Fiber Bragg Gratings, IT Techniques and Strain Gauge Validation for Strain Calculation on Aged Metal Specimens

by Ander Montero, Idurre Saez de Ocariz, Ion Lopez, Pablo Venegas, Javier Gomez and Joseba Zubia

Sensors 2011, 11(1), 1088-1104; https://doi.org/10.3390/s110101088 - 19 Jan 2011

Cited by 11 | Viewed by 13114

Abstract

This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and [...] Read more.

This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM) and Non Destructuve Evaluation (NDE) research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA) and the University of the Basque Country (UPV/EHU). Full article

(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)

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426 KiB

Open AccessArticle

A Miniature Fiber Optic Refractive Index Sensor Built in a MEMS-Based Microchannel

by Ye Tian, Wenhui Wang, Nan Wu, Xiaotian Zou, Charles Guthy and Xingwei Wang

Sensors 2011, 11(1), 1078-1087; https://doi.org/10.3390/s110101078 - 19 Jan 2011

Cited by 36 | Viewed by 11599

Abstract

A small, highly sensitive, and electromagnetic interference (EMI)-immune refractive index (RI) sensor based on the Fabry-Perot (FP) interferometer is presented. The sensor’s FP cavity was fabricated by aligning two metal-deposited, single-mode optical fiber endfaces inside a microchannel on a silicon chip. The mirrors [...] Read more.

A small, highly sensitive, and electromagnetic interference (EMI)-immune refractive index (RI) sensor based on the Fabry-Perot (FP) interferometer is presented. The sensor’s FP cavity was fabricated by aligning two metal-deposited, single-mode optical fiber endfaces inside a microchannel on a silicon chip. The mirrors on the fiber endfaces were made of thermal-deposited metal films, which provided the high finesse necessary to produce a highly sensitive sensor. Microelectromechanical systems (MEMS) fabrication techniques, specifically photolithography and deep dry etching, were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 μm. The RI change within the FP cavity was determined by demodulating the transmission spectrum phase shift. The sensitivity and finesse of the transmission spectrum were controlled by adjusting the cavity length and the thickness of the deposited metal. Our experimental results showed that the sensor’s sensitivity was 665.90 nm/RIU (RI Unit), and the limit of detection was 6 × 10⁻⁶ RIU. Using MEMS fabrication techniques to fabricate these sensors could make high yield mass production a real possibility. Multiple sensors could be integrated on a single small silicon chip to simultaneously measure RI, temperature, and biomolecule targets. Full article

(This article belongs to the Special Issue Optical Resonant Microsensors)

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670 KiB

Open AccessArticle

Formal Specification and Design Techniques for Wireless Sensor and Actuator Networks

by Diego Martínez, Apolinar González, Francisco Blanes, Raúl Aquino, José Simo and Alfons Crespo

Sensors 2011, 11(1), 1059-1077; https://doi.org/10.3390/s110101059 - 19 Jan 2011

Cited by 14 | Viewed by 10434

Abstract

A current trend in the development and implementation of industrial applications is to use wireless networks to communicate the system nodes, mainly to increase application flexibility, reliability and portability, as well as to reduce the implementation cost. However, the nondeterministic and concurrent behavior [...] Read more.

A current trend in the development and implementation of industrial applications is to use wireless networks to communicate the system nodes, mainly to increase application flexibility, reliability and portability, as well as to reduce the implementation cost. However, the nondeterministic and concurrent behavior of distributed systems makes their analysis and design complex, often resulting in less than satisfactory performance in simulation and test bed scenarios, which is caused by using imprecise models to analyze, validate and design these systems. Moreover, there are some simulation platforms that do not support these models. This paper presents a design and validation method forWireless Sensor and Actuator Networks (WSAN) which is supported on a minimal set of wireless components represented in Colored Petri Nets (CPN). In summary, the model presented allows users to verify the design properties and structural behavior of the system. Full article

(This article belongs to the Section Physical Sensors)

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Open AccessArticle

Wave Measurements Using GPS Velocity Signals

by Dong-Jiing Doong, Beng-Chun Lee and Chia Chuen Kao

Sensors 2011, 11(1), 1043-1058; https://doi.org/10.3390/s110101043 - 18 Jan 2011

Cited by 28 | Viewed by 12356

Abstract

This study presents the idea of using GPS-output velocity signals to obtain wave measurement data. The application of the transformation from a velocity spectrum to a displacement spectrum in conjunction with the directional wave spectral theory are the core concepts in this study. [...] Read more.

This study presents the idea of using GPS-output velocity signals to obtain wave measurement data. The application of the transformation from a velocity spectrum to a displacement spectrum in conjunction with the directional wave spectral theory are the core concepts in this study. Laboratory experiments were conducted to verify the accuracy of the inversed displacement of the surface of the sea. A GPS device was installed on a moored accelerometer buoy to verify the GPS-derived wave parameters. It was determined that loss or drifting of the GPS signal, as well as energy spikes occurring in the low frequency band led to erroneous measurements. Through the application of moving average skill and a process of frequency cut-off to the GPS output velocity, correlations between GPS-derived, and accelerometer buoy-measured significant wave heights and periods were both improved to 0.95. The GPS-derived one-dimensional and directional wave spectra were in agreement with the measurements. Despite the direction verification showing a 10° bias, this exercise still provided useful information with sufficient accuracy for a number of specific purposes. The results presented in this study indicate that using GPS output velocity is a reasonable alternative for the measurement of ocean waves. Full article

(This article belongs to the Section Physical Sensors)

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313 KiB

Open AccessArticle

Ionophore-Based Potentiometric Sensors for the Flow-Injection Determination of Promethazine Hydrochloride in Pharmaceutical Formulations and Human Urine

by Ahmed Khudhair Hassan, Bahruddin Saad, Sulaiman Ab Ghani, Rohana Adnan, Afidah Abdul Rahim, Norariza Ahmad, Marina Mokhtar, Suham Towfiq Ameen and Suad Mustafa Al-Araji

Sensors 2011, 11(1), 1028-1042; https://doi.org/10.3390/s110101028 - 18 Jan 2011

Cited by 14 | Viewed by 14088

Abstract

Plasticised poly(vinyl chloride)-based membranes containing the ionophores (α-, β- and γ-cyclodextrins (CD), dibenzo-18-crown-6 (DB18C6) and dibenzo-30-crown-10 (DB30C10) were evaluated for their potentiometric response towards promethazine (PM) in a flow injection analysis (FIA) set-up. Good responses were obtained when β- and γ-CDs, and DB30C10 [...] Read more.

Plasticised poly(vinyl chloride)-based membranes containing the ionophores (α-, β- and γ-cyclodextrins (CD), dibenzo-18-crown-6 (DB18C6) and dibenzo-30-crown-10 (DB30C10) were evaluated for their potentiometric response towards promethazine (PM) in a flow injection analysis (FIA) set-up. Good responses were obtained when β- and γ-CDs, and DB30C10 were used. The performance characteristics were further improved when tetrakis(4-chlorophenyl) borate (KTPB) was added to the membrane. The sensor based on β-CD, bis(2-ethylhexyl) adipate (BEHA) and KTPB exhibited the best performance among the eighteen sensor compositions that were tested. The response was linear from 1 x 10⁻⁵ to 1 x 10⁻² M, slope was 61.3 mV decade⁻¹, the pH independent region ranged from 4.5 to 7.0, a limit of detection of 5.3 x 10⁻⁶ M was possible and a lifetime of more than a month was observed when used in the FIA system. Other plasticisers such as dioctyl phenylphosphonate and tributyl phosphate do not show significant improvements in the quality of the sensors. The promising sensors were further tested for the effects of foreign ions (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Co²⁺, Cu²⁺, Cr³⁺, Fe³⁺, glucose, fructose). FIA conditions (e.g., effects of flow rate, injection volume, pH of the carrier stream) were also studied when the best sensor was used (based on β-CD). The sensor was applied to the determination of PM in four pharmaceutical preparations and human urine that were spiked with different levels of PM. Good agreement between the sensor and the manufacturer’s claimed values (for pharmaceutical preparations) was obtained, while mean recoveries of 98.6% were obtained for spiked urine samples. The molecular recognition features of the sensors as revealed by molecular modelling were rationalised by the nature of the interactions and complexation energies between the host and guest molecules. Full article

(This article belongs to the Section Chemical Sensors)

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Structure of promethazine. Full article ">
Schematic diagram of the FIA manifold. Full article ">
The three different orientations considered for the insertion of promethazine into the cavity of the host molecules with the N atom from the alkyl group of promethazine moving in (a) vertically, (b) facing up, and (c) down horizontally. Full article ">
pH profile of sensor no. 10. Carrier stream, 0.1 M acetate buffer; injection loop, 150 μL; flow rate; 3.25 mL min−1. Full article ">
Lifetime studies of promethazine sensors based on β-CD with different plasticizer (sensors 10, 13 and 16). Peak heights from the injection of promethazine standards at regular interval were noted when continuously pumped with carrier stream. Full article ">
The energy minimised structures obtained from PM3 calculations for the side and top view of (a) promethazine/α-CD, (b) promethazine/β-CD, (c) promethazine/γ-CD, (d) promethazine/DB18C6, and (e) promethazine/DB30C10 complexes. Full article ">

923 KiB

Open AccessArticle

A Simple Strategy to Mitigate the Aliasing Effect in X-band Marine Radar Data: Numerical Results for a 2D Case

by Francesco Serafino, Claudio Lugni, Josè Carlos Nieto Borge and Francesco Soldovieri

Sensors 2011, 11(1), 1009-1027; https://doi.org/10.3390/s110101009 - 18 Jan 2011

Cited by 13 | Viewed by 11039

Abstract

For moderate and high speed values of the sea surface current, an aliasing phenomenon, due to an under-sampling in the time-domain, can strongly affect the reconstruction of the sea surface elevation derived from X-band radar images. Here, we propose a de-aliasing strategy that [...] Read more.

For moderate and high speed values of the sea surface current, an aliasing phenomenon, due to an under-sampling in the time-domain, can strongly affect the reconstruction of the sea surface elevation derived from X-band radar images. Here, we propose a de-aliasing strategy that exploits the physical information provided by the dispersion law for gravity waves. In particular, we utilize simplifying hypotheses and numerical tests with synthetic data are presented to demonstrate the effectiveness of the presented method. Full article

(This article belongs to the Section Physical Sensors)

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Block diagram of the inversion procedure. Full article ">
Folded spectrum related to the parameters of <a href="#t1-sensors-11-01009" class="html-table">Table 1</a>. The dotted lines depict the replicas of the spectrum. Full article ">
Dispersion relation for the progressive waves when the surface current U changes. Full article ">
Upper panel: folded spectrum as <a href="#f2-sensors-11-01009" class="html-fig">Figure 2</a>, referred to progressive waves, before of compensating the aliasing effect. Lower panel: Unfolded spectrum obtained by applying the virtual current Ũ of <a href="#FD17" class="html-disp-formula">Equation (17)</a> to the spectrum of the upper panel. Full article ">
Plot of <a href="#FD13" class="html-disp-formula">Equation (13)</a> depicting the decreasing behaviour of the maximum allowable value km with respect to the surface current Û. Full article ">
Behaviour of ω̃(k,Ũ) (according to <a href="#FD14" class="html-disp-formula">Equation(14)</a>) for a fixed value of the surface current U = 7 m/s and for different values of the virtual surface current Uv = [0,3.05, 6.1, 12.2, 15.25, 18.3] m/s. Full article ">
Behaviour of ω̃(k, Ũ) (according to <a href="#FD14" class="html-disp-formula">Equation (14)</a>) for a fixed value of the surface current U = 7 m/s and for the two different values of the virtual surface current Uv = [11, 12.2] m/s. The dotted point accounts for the maximum point (kmax, ωmax). Full article ">
Behavior of the spectral bandwidth G(Ũ). Full article ">
Zero padded non-folded spectrum FN(ω(k),k) obtained form the spectrum of the upper panel of <a href="#f4-sensors-11-01009" class="html-fig">Figure 4</a> by applying the proposed strategy to solve the aliasing phenomenon. Full article ">

603 KiB

Open AccessArticle

Forwarding Techniques for IP Fragmented Packets in a Real 6LoWPAN Network

by Alessandro Ludovici, Anna Calveras and Jordi Casademont

Sensors 2011, 11(1), 992-1008; https://doi.org/10.3390/s110100992 - 18 Jan 2011

Cited by 30 | Viewed by 12954

Abstract

Wireless Sensor Networks (WSNs) are attracting more and more interest since they offer a low-cost solution to the problem of providing a means to deploy large sensor networks in a number of application domains. We believe that a crucial aspect to facilitate WSN [...] Read more.

Wireless Sensor Networks (WSNs) are attracting more and more interest since they offer a low-cost solution to the problem of providing a means to deploy large sensor networks in a number of application domains. We believe that a crucial aspect to facilitate WSN diffusion is to make them interoperable with external IP networks. This can be achieved by using the 6LoWPAN protocol stack. 6LoWPAN enables the transmission of IPv6 packets over WSNs based on the IEEE 802.15.4 standard. IPv6 packet size is considerably larger than that of IEEE 802.15.4 data frame. To overcome this problem, 6LoWPAN introduces an adaptation layer between the network and data link layers, allowing IPv6 packets to be adapted to the lower layer constraints. This adaptation layer provides fragmentation and header compression of IP packets. Furthermore, it also can be involved in routing decisions. Depending on which layer is responsible for routing decisions, 6LoWPAN divides routing in two categories: mesh under if the layer concerned is the adaptation layer and route over if it is the network layer. In this paper we analyze different routing solutions (route over, mesh under and enhanced route over) focusing on how they forward fragments. We evaluate their performance in terms of latency and energy consumption when transmitting IP fragmented packets. All the tests have been performed in a real 6LoWPAN implementation. After consideration of the main problems in forwarding of mesh frames in WSN, we propose and analyze a new alternative scheme based on mesh under, which we call controlled mesh under. Full article

(This article belongs to the Section Physical Sensors)

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6LoWPAN Fragment headers. (a) First fragment; (b) Subsequent fragment. Full article ">
6LoWPAN Mesh header. Full article ">
Topology for a two-hop network. In round-trip delay time tests, the base station sends ping requests to the sensor node. In end-to-end delay time tests, the sensor node originates the UDP packet flows. Current consumption is measured in the relay node. Full article ">
Round-trip delay time evolution according to ICMP payload size. Buffer congestion affects route over when reaching a payload size of 900 bytes, causing the big jump in the average round-trip delay time. Full article ">
End-to-end delay time evolution. The number of retransmissions is lower in controlled mesh under than in mesh under, resulting in a better end-to-end delay time trend. (a) End-to-end delay time for a two hops network. (b) End-to-end delay time for a three hops network. (c) End-to-end delay time for a four hops network. Full article ">
End-to-end delay time evolution. The number of retransmissions is lower in controlled mesh under than in mesh under, resulting in a better end-to-end delay time trend. (a) End-to-end delay time for a two hops network. (b) End-to-end delay time for a three hops network. (c) End-to-end delay time for a four hops network. Full article ">
Current consumption evolution according to ICMP payload size. Hop-by-hop fragment reassembling performed by route over proves to be energy demanding. The control on packet forwarding introduced in controlled mesh under, slightly increases current consumption compared with mesh under. Full article ">

375 KiB

Open AccessArticle

Multi-Channel Distributed Coordinated Function over Single Radio in Wireless Sensor Networks

by Carlene E.-A. Campbell, Kok-Keong Loo, Orhan Gemikonakli, Shafiullah Khan and Dhananjay Singh

Sensors 2011, 11(1), 964-991; https://doi.org/10.3390/s110100964 - 17 Jan 2011

Cited by 12 | Viewed by 13234

Abstract

Multi-channel assignments are becoming the solution of choice to improve performance in single radio for wireless networks. Multi-channel allows wireless networks to assign different channels to different nodes in real-time transmission. In this paper, we propose a new approach, Multi-channel Distributed Coordinated Function [...] Read more.

Multi-channel assignments are becoming the solution of choice to improve performance in single radio for wireless networks. Multi-channel allows wireless networks to assign different channels to different nodes in real-time transmission. In this paper, we propose a new approach, Multi-channel Distributed Coordinated Function (MC-DCF) which takes advantage of multi-channel assignment. The backoff algorithm of the IEEE 802.11 distributed coordination function (DCF) was modified to invoke channel switching, based on threshold criteria in order to improve the overall throughput for wireless sensor networks (WSNs) over 802.11 networks. We presented simulation experiments in order to investigate the characteristics of multi-channel communication in wireless sensor networks using an NS2 platform. Nodes only use a single radio and perform channel switching only after specified threshold is reached. Single radio can only work on one channel at any given time. All nodes initiate constant bit rate streams towards the receiving nodes. In this work, we studied the impact of non-overlapping channels in the 2.4 frequency band on: constant bit rate (CBR) streams, node density, source nodes sending data directly to sink and signal strength by varying distances between the sensor nodes and operating frequencies of the radios with different data rates. We showed that multi-channel enhancement using our proposed algorithm provides significant improvement in terms of throughput, packet delivery ratio and delay. This technique can be considered for WSNs future use in 802.11 networks especially when the IEEE 802.11n becomes popular thereby may prevent the 802.15.4 network from operating effectively in the 2.4 GHz frequency band. Full article

(This article belongs to the Section Physical Sensors)

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721 KiB

Open AccessArticle

Characterization of Carbonyl Compounds in the Ambient Air of an Industrial City in Korea

by Young-Kyo Seo and Sung-Ok Baek

Sensors 2011, 11(1), 949-963; https://doi.org/10.3390/s110100949 - 17 Jan 2011

Cited by 21 | Viewed by 10064

Abstract

The purpose of this study was to characterize spatial and temporal variations of carbonyl compounds in Gumi city, where a number of large electronic-industrial complexes are located. Carbonyl samples were collected at five sites in the Gumi area: three industrial, one commercial, and [...] Read more.

The purpose of this study was to characterize spatial and temporal variations of carbonyl compounds in Gumi city, where a number of large electronic-industrial complexes are located. Carbonyl samples were collected at five sites in the Gumi area: three industrial, one commercial, and one residential area. Sampling was carried out throughout a year from December 2003 to November 2004. At one industrial site, samples were taken every six days, while those of the other sites were for seven consecutive days in every season. Each sample was collected for 150 minutes and at intervals of three times a day (morning, afternoon, and evening). A total of 476 samples were analyzed to determine 15 carbonyl compounds by the USEPA TO-11A (DNPH-cartridge/HPLC) method. In general, acetaldehyde appeared to be the most abundant compound, followed by formaldehyde, and acetone+acrolein. Mean concentrations of acetaldehyde were two to three times higher in the industrial sites than in the other sites, with its maximum of 77.7 ppb. In contrast, ambient levels of formaldehyde did not show any significant difference between the industrial and non-industrial groups. Its concentrations peaked in summer probably due to the enhanced volatilization and photochemical reactivity. These results indicate significant emission sources of acetaldehyde in the Gumi industrial complexes. Mean concentrations of organic solvents (such as acetone+acrolein and methyl ethyl ketone) were also significantly high in industrial areas. In conclusion, major sources of carbonyl compounds, including acetaldehyde, are strongly associated with industrial activities in the Gumi city area. Full article

(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)

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551 KiB

Open AccessArticle

RFID Label Tag Design for Metallic Surface Environments

by Chong Ryol Park and Ki Hwan Eom

Sensors 2011, 11(1), 938-948; https://doi.org/10.3390/s110100938 - 17 Jan 2011

Cited by 18 | Viewed by 8580

Abstract

This paper describes a metal mount RFID tag that works reliably on metallic surfaces. The method proposes the use of commercial label type RFID tags with 2.5 mm thick Styrofoam103.7 with a relative permittivity of 1.03 attached on the back of the tag. [...] Read more.

This paper describes a metal mount RFID tag that works reliably on metallic surfaces. The method proposes the use of commercial label type RFID tags with 2.5 mm thick Styrofoam103.7 with a relative permittivity of 1.03 attached on the back of the tag. In order to verify the performance of the proposed method, we performed experiments on an electric transformer supply chain system. The experimental results showed that the proposed tags can communicate with readers from a distance of 2 m. The recognition rates are comparable to those of commercial metallic mountable tags. Full article

(This article belongs to the Special Issue Selected Papers from The 2nd International Conference on Advanced Science and Technology)

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495 KiB

Open AccessArticle

Data-Centric Multiobjective QoS-Aware Routing Protocol for Body Sensor Networks

by Md. Abdur Razzaque, Choong Seon Hong and Sungwon Lee

Sensors 2011, 11(1), 917-937; https://doi.org/10.3390/s110100917 - 17 Jan 2011

Cited by 142 | Viewed by 11724

Abstract

In this paper, we address Quality-of-Service (QoS)-aware routing issue for Body Sensor Networks (BSNs) in delay and reliability domains. We propose a data-centric multiobjective QoS-Aware routing protocol, called DMQoS, which facilitates the system to achieve customized QoS services for each traffic category differentiated [...] Read more.

In this paper, we address Quality-of-Service (QoS)-aware routing issue for Body Sensor Networks (BSNs) in delay and reliability domains. We propose a data-centric multiobjective QoS-Aware routing protocol, called DMQoS, which facilitates the system to achieve customized QoS services for each traffic category differentiated according to the generated data types. It uses modular design architecture wherein different units operate in coordination to provide multiple QoS services. Their operation exploits geographic locations and QoS performance of the neighbor nodes and implements a localized hop-by-hop routing. Moreover, the protocol ensures (almost) a homogeneous energy dissipation rate for all routing nodes in the network through a multiobjective Lexicographic Optimization-based geographic forwarding. We have performed extensive simulations of the proposed protocol, and the results show that DMQoS has significant performance improvements over several state-of-the-art approaches. Full article

(This article belongs to the Section Physical Sensors)

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341 KiB

Open AccessArticle

Detection of Single Molecules Illuminated by a Light-Emitting Diode

by Ilja Gerhardt, Lijian Mai, Antìa Lamas-Linares and Christian Kurtsiefer

Sensors 2011, 11(1), 905-916; https://doi.org/10.3390/s110100905 - 14 Jan 2011

Cited by 17 | Viewed by 9588

Abstract

Optical detection and spectroscopy of single molecules has become an indispensable tool in biological imaging and sensing. Its success is based on fluorescence of organic dye molecules under carefully engineered laser illumination. In this paper we demonstrate optical detection of single molecules on [...] Read more.

Optical detection and spectroscopy of single molecules has become an indispensable tool in biological imaging and sensing. Its success is based on fluorescence of organic dye molecules under carefully engineered laser illumination. In this paper we demonstrate optical detection of single molecules on a wide-field microscope with an illumination based on a commercially available, green light-emitting diode. The results are directly compared with laser illumination in the same experimental configuration. The setup and the limiting factors, such as light transfer to the sample, spectral filtering and the resulting signal-to-noise ratio are discussed. A theoretical and an experimental approach to estimate these parameters are presented. The results can be adapted to other single emitter and illumination schemes. Full article

(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)

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Experimental Setup, consisting of a confocal microscope (detection not shown) with wide-field configuration. A flip mirror allows to switch between laser and LED type illumination. Inset: Two lens LED-assembly, the LED is mounted with thermal grease directly onto a 3 stage thermo-electric cooler (TEC), which is attached to a fan-cooled heat sink. Full article ">
Measured light emission directly in front of light-emitting diode mounted in the diode assembly. The dashed line shows the nominal maximal current of 700 mA. Full article ">
Absorption spectrum of terrylene and the emission spectrum of the unfiltered LED. The dashed line represents the wavelength of the frequency-doubled Nd:YAG laser. The irradiance of one to the other shows a by 40% larger value for the LED illumination. The larger spectral overlap allows a more efficient excitation. Inset: Terrylene (left) and the matrix molecule p-terphenyl (right). Full article ">
Emission spectrum of terrylene molecules. The optimal spectral filtering utilizes a similar slope to the emission spectrum of the molecule. In our experimental configuration a long-pass filter was slanted to match the excitation filter with a falling slope around 585 nm. Full article ">
Direct comparison of two wide-field images acquired by laser (a) and LED illumination (b). The gray levels of the images have been adapted to account for the increased background with the LED illumination. Still the slightly weaker signal to noise ratio is obvious. To have a direct comparison the camera levels are presented uncorrected in figure (c). The background level of the camera is at 13% (blocking the excitation light) and should be subtracted for both illuminations. Light leakage through the filters increases the LED illumination background level to more than 60%. Full article ">

762 KiB

Open AccessArticle

Porphyrin-Embedded Silicate Materials for Detection of Hydrocarbon Solvents

by Brandy J. Johnson, Nicole E. Anderson, Paul T. Charles, Anthony P. Malanoski, Brian J. Melde, Mansoor Nasir and Jeffrey R. Deschamps

Sensors 2011, 11(1), 886-904; https://doi.org/10.3390/s110100886 - 14 Jan 2011

Cited by 30 | Viewed by 12134

Abstract

The development of porphyrin-embedded mesoporous organosilicate materials for application to the detection of volatile hydrocarbon solvents is described. Design of the receptor and optical indicator construct begins with parallel selection of the porphyrin indicator and design of the mesoporous sorbent. For the porphyrin [...] Read more.

The development of porphyrin-embedded mesoporous organosilicate materials for application to the detection of volatile hydrocarbon solvents is described. Design of the receptor and optical indicator construct begins with parallel selection of the porphyrin indicator and design of the mesoporous sorbent. For the porphyrin indicator, high binding affinity and strong changes in spectrophotometric character upon target interaction are desired. The sorbent should provide high target binding capacity and rapid binding kinetics. A number of porphyrin/metalloporphyrin variants and organosilicate sorbents were evaluated to determine the characteristics of their interaction with the targets, benzene, toluene, and hexane. The selected porphyrin candidates were covalently immobilized within a benzene-bridged sorbent. This construct was applied to the detection of targets using both fluorescence- and reflectance-based protocols. The use of red, green, and blue (RGB) color values from the constructs in a highly simplified detection scheme is described. Full article

(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)

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Structures of the porphyrin parent compound and those porphyrins used in the presented studies; from left to right: porphine; 5-mono(4-carboxyphenyl)-10, 15,20-triphenyl porphine (C1TPP); meso-tri(4-sulfonatophenyl)mono(4-carboxyphenyl) porphine (C1S3TPP); and meso-tetra(4-carboxyphenyl) porphine (C4TPP). Metal complex formation occurs through interaction of the central nitrogen atoms indicated here with an ‘X’. Full article ">
Synthesis of organosilicate sorbents. Full article ">
Structural characterization. Panel A, nitrogen sorption isotherms (BP2 offset by 325 cm3/g). Panel B, pore size distributions. Panel C, XRD spectra. B100 (blue), BP2 (red), OTS (black). Full article ">
Binding kinetics from vapor phase. Shown here are the kinetics of benzene binding for each of the organosilicate materials. Benzene (53 mg) was allowed to diffuse within a volume of 125 mL for the indicated time (20 °C). Panel A, B100 (black), OTS (red), and BP2 (gray). Panel B, DEB (orange), Ph1 (green), PhE1 (blue), and TM1 (purple). Full article ">
Changes in the porphyrin absorbance characteristics upon interaction with targets. Panel A, absorbance spectra of MnC1TPP (4 μM) in the absence (black) and presence of benzene (red), toluene (blue), and hexanes (green) (200 mM, in 95% methanol). Panel B, difference spectra calculated as post-exposure minus pre-exposure absorbance from Panel A. In this spectrum, the distance between the peak position and the trough position (Δλ) and the difference between the peak height and the trough depth (ΔI) are indicated for the benzene interaction. Panel C, difference spectra resulting from the exposure of ZnC4TPP (3.3 μM) to varying concentrations of toluene. Panel D, concentration dependence of the interaction between ZnC4TPP and the three targets. Results for additional metalloporphyrins are provided in <a href="#SD1" class="html-supplementary-material">Supporting Information, Figure S3</a>. Full article ">
Interaction of targets with FeC1TPP-embedded B100. Panel A, fluorescence excitation and emission spectra for the FeC1TPP-embedded B100 material (2 mg) in the absence (blue) and presence of 3.5 mg (gray), 5.3 mg (black), and 12 mg (red) benzene. Panel B, difference fluorescence spectra for exposure of the material to benzene. Panel C, binding isotherms for the interaction of FeC1TPP-embedded B100 with benzene (425 and 414 nm) and hexanes (417 and 415 nm) based on the peak/trough difference in intensity. Results for additional metalloporphyrins are provided in <a href="#SD1" class="html-supplementary-material">Supporting Information, Figures S4</a> through <a href="#SD1" class="html-supplementary-material">S9</a>. Full article ">
Interaction of FeC1TPP-embedded B100 with targets. Shown here are scanner images of the material following exposure to varying concentrations of benzene. Also shown are simulated images generated based on average RGB values for FeC1TPP-embedded B100 following exposure to varying target concentrations and the dependence of RGB image color values on target concentration for the interaction of benzene with FeC1TPP-embedded B100 (red circles = R, blue triangles = B, green squares = G). Complete data for other materials/targets is presented in the <a href="#SD1" class="html-supplementary-material">Supporting Information, Figures S4</a> through <a href="#SD1" class="html-supplementary-material">S9</a>. Full article ">
Reflectance spectra. Shown here are the reflectance spectra generated for MnC4TPP-embedded B100 (black, Panel A) and C1TPP-embedded B100 (black, Panel B) from the RGB values using the algorithm. Also shown are the spectra observed following exposure (2.4 g/g) of the materials to benzene (red), toluene (blue), and hexane (green). Panel C shows the change in the reflectance spectrum for FeC1TPP-embedded B100 as the concentration of benzene is increased from 0 to 2.4 g/g. Panel D presents difference spectra to highlight the variations specific to each target (benzene (red), toluene (blue), and hexane (green)) on interaction with C1TPP-embedded B100. Complete reflectance spectra sets for other materials/targets are presented in the <a href="#SD1" class="html-supplementary-material">Supporting Information, Figures S11</a> to <a href="#SD1" class="html-supplementary-material">S16</a>. Full article ">

426 KiB

Open AccessArticle

Hall Sensors for Extreme Temperatures

by Jakub Jankowski, Semir El-Ahmar and Maciej Oszwaldowski

Sensors 2011, 11(1), 876-885; https://doi.org/10.3390/s110100876 - 14 Jan 2011

Cited by 46 | Viewed by 12159

Abstract

We report on the preparation of the first complete extreme temperature Hall sensor. This means that the extreme-temperature magnetic sensitive semiconductor structure is built-in an extreme-temperature package especially designed for that purpose. The working temperature range of the sensor extends from −270 °C [...] Read more.

We report on the preparation of the first complete extreme temperature Hall sensor. This means that the extreme-temperature magnetic sensitive semiconductor structure is built-in an extreme-temperature package especially designed for that purpose. The working temperature range of the sensor extends from −270 °C to +300 °C. The extreme-temperature Hall-sensor active element is a heavily n-doped InSb layer epitaxially grown on GaAs. The magnetic sensitivity of the sensor is ca. 100 mV/T and its temperature coefficient is less than 0.04 %/K. This sensor may find applications in the car, aircraft, spacecraft, military and oil and gas industries. Full article

(This article belongs to the Section Physical Sensors)

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Extreme-temperature Hall sensor; (a) ETHS structure. Maltese cross-shaped InSb layer is plated with Cr-Au electrodes, and (b) ETHS in an open ET package. Full article ">
Effect of annealing on ET Hall sensors B2 and B3 performed at temperatures 350 °C and 300 °C; (a) change of Hall voltage, UH, (b) change of input resistance, R. Full article ">
Temperature dependence of (a) Hall voltage UH, and (b) resistance R sensors B2 and B3. Full article ">
Field dependence of Hall voltage UH in range (0–8) T at 20 °C and −269 °C for sensors B2 and B3. This d0ependence at low magnetic fields is given in insert. Full article ">
Field dependence of relative magnetoresistance ΔR/R0 in the range (0–8) T at 20 °C and −269 °C for sensors B2 and B3. This dependence was obtained from the measured dependence R(B) shown in inserts. Full article ">

678 KiB

Open AccessArticle

A Simple Method Based on the Application of a CCD Camera as a Sensor to Detect Low Concentrations of Barium Sulfate in Suspension

by Rodrigo Caciano de Sena, Matheus Soares, Maria Luiza Oliveira Pereira, Rogério Cruz Domingues da Silva, Francisca Ferreira do Rosário and Joao Francisco Cajaiba da Silva

Sensors 2011, 11(1), 864-875; https://doi.org/10.3390/s110100864 - 13 Jan 2011

Cited by 28 | Viewed by 12068

Abstract

The development of a simple, rapid and low cost method based on video image analysis and aimed at the detection of low concentrations of precipitated barium sulfate is described. The proposed system is basically composed of a webcam with a CCD sensor and [...] Read more.

The development of a simple, rapid and low cost method based on video image analysis and aimed at the detection of low concentrations of precipitated barium sulfate is described. The proposed system is basically composed of a webcam with a CCD sensor and a conventional dichroic lamp. For this purpose, software for processing and analyzing the digital images based on the RGB (Red, Green and Blue) color system was developed. The proposed method had shown very good repeatability and linearity and also presented higher sensitivity than the standard turbidimetric method. The developed method is presented as a simple alternative for future applications in the study of precipitations of inorganic salts and also for detecting the crystallization of organic compounds. Full article

(This article belongs to the Section Chemical Sensors)

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Set-up of the measuring system (1-webcam; 2-light source; 3-stirrer; 4-temperature sensor, 5-turbidity sensor). Full article ">
Effect of camera configurations on the output RGB signal obtained from a blank solution: (a) configuration A; (b) configuration B; (c) configuration C. Full article ">
Images obtained from a blank solution by using different camera configurations: (a) camera configuration A; (b) camera configuration B; (c) camera configuration C. Full article ">
Red, Green and Blue channel levels for different concentrations of barium sulfate in suspension: (a) configuration A, (b) configuration C. Full article ">
Red, Green and Blue channel levels for different concentrations of barium sulfate in suspension: (a) configuration A, (b) configuration C. Full article ">
Images of barium sulfate suspensions of different concentration: (a) blank solution, (b) 2.5 mg/L, (c) 5 mg/L, (d) 7.5 mg/L, (e) 10 mg/L, (f) 25 mg/L, (g) 100 mg/L, (h) 250 mg/L. Full article ">
Analytical curves: (a) video image analysis—configuration A; (b) video image analysis—configuration B; (c) output of the turbidity sensor. Full article ">

408 KiB

Open AccessArticle

A Multiple Mobility Support Approach (MMSA) Based on PEAS for NCW in Wireless Sensor Networks

by Bong-Joo Koo, Seog-Bong Kim, Jong-Yil Park and Kang-Min Park

Sensors 2011, 11(1), 852-863; https://doi.org/10.3390/s110100852 - 13 Jan 2011

Cited by 1 | Viewed by 9484

Abstract

Wireless Sensor Networks (WSNs) can be implemented as one of sensor systems in Network Centric Warfare (NCW). Mobility support and energy efficiency are key concerns for this application, due to multiple mobile users and stimuli in real combat field. However, mobility support approaches [...] Read more.

Wireless Sensor Networks (WSNs) can be implemented as one of sensor systems in Network Centric Warfare (NCW). Mobility support and energy efficiency are key concerns for this application, due to multiple mobile users and stimuli in real combat field. However, mobility support approaches that can be adopted in this circumstance are rare. This paper proposes Multiple Mobility Support Approach (MMSA) based on Probing Environment and Adaptive Sleeping (PEAS) to support the simultaneous mobility of both multiple users and stimuli by sharing the information of stimuli in WSNs. Simulations using Qualnet are conducted, showing that MMSA can support multiple mobile users and stimuli with good energy efficiency. It is expected that the proposed MMSA can be applied to real combat field. Full article

(This article belongs to the Section Physical Sensors)

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1306 KiB

Open AccessReview

Low-Dimensional Palladium Nanostructures for Fast and Reliable Hydrogen Gas Detection

by Jin-Seo Noh, Jun Min Lee and Wooyoung Lee

Sensors 2011, 11(1), 825-851; https://doi.org/10.3390/s110100825 - 13 Jan 2011

Cited by 139 | Viewed by 15328

Abstract

Palladium (Pd) has received attention as an ideal hydrogen sensor material due to its properties such as high sensitivity and selectivity to hydrogen gas, fast response, and operability at room temperature. Interestingly, various Pd nanostructures that have been realized by recent developments in [...] Read more.

Palladium (Pd) has received attention as an ideal hydrogen sensor material due to its properties such as high sensitivity and selectivity to hydrogen gas, fast response, and operability at room temperature. Interestingly, various Pd nanostructures that have been realized by recent developments in nanotechnologies are known to show better performance than bulk Pd. This review highlights the characteristic properties, issues, and their possible solutions of hydrogen sensors based on the low-dimensional Pd nanostructures with more emphasis on Pd thin films and Pd nanowires. The finite size effects, relative strengths and weaknesses of the respective Pd nanostructures are discussed in terms of performance, manufacturability, and practical applicability. Full article

(This article belongs to the Special Issue Gas Sensors - 2010)

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1253 KiB

Open AccessReview

Recent Advances in the Design of Electro-Optic Sensors for Minimally Destructive Microwave Field Probing

by Dong-Joon Lee, No-Weon Kang, Jun-Ho Choi, Junyeon Kim and John F. Whitaker

Sensors 2011, 11(1), 806-824; https://doi.org/10.3390/s110100806 - 12 Jan 2011

Cited by 45 | Viewed by 14612

Abstract

In this paper we review recent design methodologies for fully dielectric electro-optic sensors that have applications in non-destructive evaluation (NDE) of devices and materials that radiate, guide, or otherwise may be impacted by microwave fields. In many practical NDE situations, fiber-coupled-sensor configurations are [...] Read more.

In this paper we review recent design methodologies for fully dielectric electro-optic sensors that have applications in non-destructive evaluation (NDE) of devices and materials that radiate, guide, or otherwise may be impacted by microwave fields. In many practical NDE situations, fiber-coupled-sensor configurations are preferred due to their advantages over free-space bulk sensors in terms of optical alignment, spatial resolution, and especially, a low degree of field invasiveness. We propose and review five distinct types of fiber-coupled electro-optic sensor probes. The design guidelines for each probe type and their performances in absolute electric-field measurements are compared and summarized. Full article

(This article belongs to the Section Physical Sensors)

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1011 KiB

Open AccessReview

Optical Microspherical Resonators for Biomedical Sensing

by Silvia Soria, Simone Berneschi, Massimo Brenci, Franco Cosi, Gualtiero Nunzi Conti, Stefano Pelli and Giancarlo C. Righini

Sensors 2011, 11(1), 785-805; https://doi.org/10.3390/s110100785 - 12 Jan 2011

Cited by 109 | Viewed by 18688

Abstract

Optical resonators play an ubiquitous role in modern optics. A particular class of optical resonators is constituted by spherical dielectric structures, where optical rays are total internal reflected. Due to minimal reflection losses and to potentially very low material absorption, these guided modes, [...] Read more.

Optical resonators play an ubiquitous role in modern optics. A particular class of optical resonators is constituted by spherical dielectric structures, where optical rays are total internal reflected. Due to minimal reflection losses and to potentially very low material absorption, these guided modes, known as whispering gallery modes, can confer the resonator an exceptionally high quality factor Q, leading to high energy density, narrow resonant-wavelength lines and a lengthy cavity ringdown. These attractive characteristics make these miniaturized optical resonators especially suited as laser cavities and resonant filters, but also as very sensitive sensors. First, a brief analysis is presented of the characteristics of microspherical resonators, of their fabrication methods, and of the light coupling techniques. Then, we attempt to overview some of the recent advances in the development of microspherical biosensors, underlining a number of important applications in the biomedical field. Full article

(This article belongs to the Special Issue Optical Resonant Microsensors)

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387 KiB

Open AccessArticle

Directional MAC Approach for Wireless Body Area Networks

by Md. Asdaque Hussain, Md. Nasre Alam and Kyung Sup Kwak

Sensors 2011, 11(1), 771-784; https://doi.org/10.3390/s110100771 - 12 Jan 2011

Cited by 11 | Viewed by 13574

Abstract

Wireless Body Area Networks (WBANs) designed for medical, sports, and entertainment applications, have drawn the attention of academia and industry alike. A WBAN is a special purpose network, designed to operate autonomously to connect various medical sensors and appliances, located inside and/or outside [...] Read more.

Wireless Body Area Networks (WBANs) designed for medical, sports, and entertainment applications, have drawn the attention of academia and industry alike. A WBAN is a special purpose network, designed to operate autonomously to connect various medical sensors and appliances, located inside and/or outside of a human body. This network enables physicians to remotely monitor vital signs of patients and provide real time feedback for medical diagnosis and consultations. The WBAN system can offer two significant advantages: patient mobility due to their use of portable monitoring devices and a location independent monitoring facility. With its appealing dimensions, it brings about a new set of challenges, which we do not normally consider in such small sensor networks. It requires a scalable network in terms of heterogeneous data traffic, low power consumption of sensor nodes, integration in and around the body networking and coexistence. This work presents a medium access control protocol for WBAN which tries to overcome the aforementioned challenges. We consider the use of multiple beam adaptive arrays (MBAA) at BAN Coordinator (BAN_C) node. When used as a BAN_C, an MBAA can successfully receive two or more overlapping packets at the same time. Each beam captures a different packet by automatically pointing its pattern toward one packet while annulling other contending packets. This paper describes how an MBAA can be integrated into a single hope star topology as a BAN_C. Simulation results show the performance of our proposed protocol. Full article

(This article belongs to the Section Physical Sensors)

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426 KiB

Open AccessArticle

Fringe Capacitance Correction for a Coaxial Soil Cell

by Mathew G. Pelletier, Joseph A. Viera, Robert C. Schwartz, Robert J. Lascano, Steven R. Evett, Tim R. Green, John D. Wanjura and Greg A. Holt

Sensors 2011, 11(1), 757-770; https://doi.org/10.3390/s110100757 - 12 Jan 2011

Cited by 4 | Viewed by 11082

Abstract

Accurate measurement of moisture content is a prime requirement in hydrological, geophysical and biogeochemical research as well as for material characterization and process control. Within these areas, accurate measurements of the surface area and bound water content is becoming increasingly important for providing [...] Read more.

Accurate measurement of moisture content is a prime requirement in hydrological, geophysical and biogeochemical research as well as for material characterization and process control. Within these areas, accurate measurements of the surface area and bound water content is becoming increasingly important for providing answers to many fundamental questions ranging from characterization of cotton fiber maturity, to accurate characterization of soil water content in soil water conservation research to bio-plant water utilization to chemical reactions and diffusions of ionic species across membranes in cells as well as in the dense suspensions that occur in surface films. One promising technique to address the increasing demands for higher accuracy water content measurements is utilization of electrical permittivity characterization of materials. This technique has enjoyed a strong following in the soil-science and geological community through measurements of apparent permittivity via time-domain-reflectometry (TDR) as well in many process control applications. Recent research however, is indicating a need to increase the accuracy beyond that available from traditional TDR. The most logical pathway then becomes a transition from TDR based measurements to network analyzer measurements of absolute permittivity that will remove the adverse effects that high surface area soils and conductivity impart onto the measurements of apparent permittivity in traditional TDR applications. This research examines an observed experimental error for the coaxial probe, from which the modern TDR probe originated, which is hypothesized to be due to fringe capacitance. The research provides an experimental and theoretical basis for the cause of the error and provides a technique by which to correct the system to remove this source of error. To test this theory, a Poisson model of a coaxial cell was formulated to calculate the effective theoretical extra length caused by the fringe capacitance which is then used to correct the experimental results such that experimental measurements utilizing differing coaxial cell diameters and probe lengths, upon correction with the Poisson model derived correction factor, all produce the same results thereby lending support and for an augmented measurement technique for measurement of absolute permittivity. Full article

(This article belongs to the Section Chemical Sensors)

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Reflection/transmission map detail of resultant waveform from combination of multiple reflections from both the leading edge, undesired, and probe end, desired measurement, in TDR/FDR probes, or coaxial cells, due to impedance miss-match between inter-connecting coaxial cable’s impedance, of Zo, to the soil-probe impedance of Z1. Note: Hatched area indicates soil or other material under test. Full article ">
Machined brass coaxial cells based on commercial N to UHF (RF) adapter. System utilizes an insert based center probe that allows for changing the center probe, thereby providing a center-probe length change for the system, while maintaining the original calibration that removes the effects of the instrument, interfacing cable and the RF adapter, while preserving the original system calibration. On the right is the large brass insert that provides a similar means to maintain the original system calibration while providing the means to alter the outer diameter of the coaxial cell, hence altering the impedance, of the coaxial cell. This system was designed with the center insert installed, to provide a near perfect 50 Ω match for the coaxial cell when filled with dry sand εr = 2.85. Full article ">
Poisson cross-sectional model of coaxial cell with terminated center conductor, which is the notched area at the bottom of the screen. The color pictorial is of the electric-potential inside a cross-section of a coaxial, or TDR probe with symmetry boundary conditions applied along the bottom edge (not including the notched section which represents the center conductor and has an imposed Voltage). The left and top edge of the figure have a zero voltage boundary condition representing the conductors being tied to ground and the far right edge was set to a floating boundary condition to represent an open-ended coaxial cell in a homogenous media. Full article ">
Comparison of the capacitance as calculated from the Poisson cross-sectional model of coaxial cell with terminated center conductor, as a function of the center conductor’s probe length. Full article ">

479 KiB

Open AccessArticle

A Low Cost Concept for Data Acquisition Systems Applied to Decentralized Renewable Energy Plants

by Sandro C. S. Jucá, Paulo C. M. Carvalho and Fábio T. Brito

Sensors 2011, 11(1), 743-756; https://doi.org/10.3390/s110100743 - 12 Jan 2011

Cited by 37 | Viewed by 13801

Abstract

The present paper describes experiences of the use of monitoring and data acquisition systems (DAS) and proposes a new concept of a low cost DAS applied to decentralized renewable energy (RE) plants with an USB interface. The use of such systems contributes to [...] Read more.

The present paper describes experiences of the use of monitoring and data acquisition systems (DAS) and proposes a new concept of a low cost DAS applied to decentralized renewable energy (RE) plants with an USB interface. The use of such systems contributes to disseminate these plants, recognizing in real time local energy resources, monitoring energy conversion efficiency and sending information concerning failures. These aspects are important, mainly for developing countries, where decentralized power plants based on renewable sources are in some cases the best option for supplying electricity to rural areas. Nevertheless, the cost of commercial DAS is still a barrier for a greater dissemination of such systems in developing countries. The proposed USB based DAS presents a new dual clock operation philosophy, in which the acquisition system contains two clock sources for parallel information processing from different communication protocols. To ensure the low cost of the DAS and to promote the dissemination of this technology in developing countries, the proposed data acquisition firmware and the software for USB microcontrollers programming is a free and open source software, executable in the Linux and Windows® operating systems. Full article

(This article belongs to the Section Physical Sensors)

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965 KiB

Open AccessArticle

CAROLS: A New Airborne L-Band Radiometer for Ocean Surface and Land Observations

by Mehrez Zribi, Mickael Pardé, Jacquline Boutin, Pascal Fanise, Daniele Hauser, Monique Dechambre, Yann Kerr, Marion Leduc-Leballeur, Gilles Reverdin, Niels Skou, Sten Søbjærg, Clement Albergel, Jean Christophe Calvet, Jean Pierre Wigneron, Ernesto Lopez-Baeza, Antonio Rius and Joseph Tenerelli

Sensors 2011, 11(1), 719-742; https://doi.org/10.3390/s110100719 - 12 Jan 2011

Cited by 48 | Viewed by 15530

Abstract

The “Cooperative Airborne Radiometer for Ocean and Land Studies” (CAROLS) L-Band radiometer was designed and built as a copy of the EMIRAD II radiometer constructed by the Technical University of Denmark team. It is a fully polarimetric and direct sampling correlation radiometer. It [...] Read more.

The “Cooperative Airborne Radiometer for Ocean and Land Studies” (CAROLS) L-Band radiometer was designed and built as a copy of the EMIRAD II radiometer constructed by the Technical University of Denmark team. It is a fully polarimetric and direct sampling correlation radiometer. It is installed on board a dedicated French ATR42 research aircraft, in conjunction with other airborne instruments (C-Band scatterometer—STORM, the GOLD-RTR GPS system, the infrared CIMEL radiometer and a visible wavelength camera). Following initial laboratory qualifications, three airborne campaigns involving 21 flights were carried out over South West France, the Valencia site and the Bay of Biscay (Atlantic Ocean) in 2007, 2008 and 2009, in coordination with in situ field campaigns. In order to validate the CAROLS data, various aircraft flight patterns and maneuvers were implemented, including straight horizontal flights, circular flights, wing and nose wags over the ocean. Analysis of the first two campaigns in 2007 and 2008 leads us to improve the CAROLS radiometer regarding isolation between channels and filter bandwidth. After implementation of these improvements, results show that the instrument is conforming to specification and is a useful tool for Soil Moisture and Ocean Salinity (SMOS) satellite validation as well as for specific studies on surface soil moisture or ocean salinity. Full article

(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)

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2225 KiB

Open AccessReview

Ge-Photodetectors for Si-Based Optoelectronic Integration

by Jian Wang and Sungjoo Lee

Sensors 2011, 11(1), 696-718; https://doi.org/10.3390/s110100696 - 12 Jan 2011

Cited by 221 | Viewed by 21941

Abstract

High speed photodetectors are a key building block, which allow a large wavelength range of detection from 850 nm to telecommunication standards at optical fiber band passes of 1.3–1.55 µm. Such devices are key components in several applications such as local area networks, [...] Read more.

High speed photodetectors are a key building block, which allow a large wavelength range of detection from 850 nm to telecommunication standards at optical fiber band passes of 1.3–1.55 µm. Such devices are key components in several applications such as local area networks, board to board, chip to chip and intrachip interconnects. Recent technological achievements in growth of high quality SiGe/Ge films on Si wafers have opened up the possibility of low cost Ge-based photodetectors for near infrared communication bands and high resolution spectral imaging with high quantum efficiencies. In this review article, the recent progress in the development and integration of Ge-photodetectors on Si-based photonics will be comprehensively reviewed, along with remaining technological issues to be overcome and future research trends. Full article

(This article belongs to the Special Issue Photodetectors and Imaging Technologies)

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Sensors, Volume 11, Issue 1 (January 2011) – 66 articles , Pages 1-1245

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