Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
On Whitespace Identification Using Randomly Deployed Sensors  [PDF]
Rahul Vaze,Chandra R. Murthy
Mathematics , 2012,
Abstract: This work considers the identification of the available whitespace, i.e., the regions that are not covered by any of the existing transmitters, within a given geographical area. To this end, $n$ sensors are deployed at random locations within the area. These sensors detect for the presence of a transmitter within their radio range $r_s$, and their individual decisions are combined to estimate the available whitespace. The limiting behavior of the recovered whitespace as a function of $n$ and $r_s$ is analyzed. It is shown that both the fraction of the available whitespace that the nodes fail to recover as well as their radio range both optimally scale as $\log(n)/n$ as $n$ gets large. The analysis is extended to the case of unreliable sensors, and it is shown that, surprisingly, the optimal scaling is still $\log(n)/n$ even in this case. A related problem of estimating the number of transmitters and their locations is also analyzed, with the sum absolute error in localization as performance metric. The optimal scaling of the radio range and the necessary minimum transmitter separation is determined, that ensure that the sum absolute error in transmitter localization is minimized, with high probability, as $n$ gets large. Finally, the optimal distribution of sensor deployment is determined, given the distribution of the transmitters, and the resulting performance benefit is characterized.
Bridge Deck Load Testing Using Sensors and Optical Survey Equipment  [PDF]
Hubo Cai,Osama Abudayyeh,Ikhlas Abdel-Qader,Upul Attanayake,Joseph Barbera,Eyad Almaita
Advances in Civil Engineering , 2012, DOI: 10.1155/2012/493983
Abstract: Bridges are under various loads and environmental impacts that cause them to lose their structural integrity. A significant number of bridges in US are either structurally deficient or functionally obsolete, requiring immediate attention. Nondestructive load testing is an effective approach to measure the structural response of a bridge under various loading conditions and to determine its structural integrity. This paper presents a load-test study that evaluated the response of a prefabricated bridge with full-depth precast deck panels in Michigan. This load-test program integrates optical surveying systems, a sensor network embedded in bridge decks, and surface deflection analysis. Its major contribution lies in the exploration of an embedded sensor network that was installed initially for long-term bridge monitoring in bridge load testing. Among a number of lessons learned, it is concluded that embedded sensor network has a great potential of providing an efficient and accurate approach for obtaining real-time equivalent static stresses under varying loading scenarios. 1. Introduction Bridges are a critical component of a nation’s ground transportation infrastructure system that allows the movement of people and goods from one place to another. Bridges are exposed to load effects and weather impacts that lead to their deterioration. Federal Highway Administration (FHWA) statistics show that about 20% of the National Highway System (NHS) bridges and 27% of non-NHS bridges in US are either structurally deficient or functionally obsolete [1], resulting in a total of about 152,000 bridges requiring immediate attention in the form of repair or replacement. Therefore, routine inspection and load testing are needed to obtain good estimates on bridge response and to support making decisions of appropriate maintenance and rehabilitation activities to ensure their structural integrity and safety [2, 3]. A recent trend in bridge management is the utilization of sensors embedded in the bridge structure to monitor the long-term performance of bridges, under various loads and environmental impacts. Given the monitored data, meaningful information regarding the bridge reliability can be extracted [4]. This is particularly true with the growing adoption of the prefabrication technology in bridge construction. This technology allows the prefabrication of structural components to be conducted offsite under a well-controlled environment with the benefit of higher-quality precast structural components that are expected to perform better with lower maintenance needs,
On the Displacement for Covering a Unit Interval with Randomly Placed Sensors  [PDF]
Rafa? Kapelko,Evangelos Kranakis
Computer Science , 2015,
Abstract: Consider $n$ mobile sensors placed independently at random with the uniform distribution on a barrier represented as the unit line segment $[0,1]$. The sensors have identical sensing radius, say $r$. When a sensor is displaced on the line a distance equal to $d$ it consumes energy (in movement) which is proportional to some (fixed) power $a > 0$ of the distance $d$ traveled. The energy consumption of a system of $n$ sensors thus displaced is defined as the sum of the energy consumptions for the displacement of the individual sensors. We focus on the problem of energy efficient displacement of the sensors so that in their final placement the sensor system ensures coverage of the barrier and the energy consumed for the displacement of the sensors to these final positions is minimized in expectation. In particular, we analyze the problem of displacing the sensors from their initial positions so as to attain coverage of the unit interval and derive trade-offs for this displacement as a function of the sensor range. We obtain several tight bounds in this setting thus generalizing several of the results of [12] to any power $a >0$.
Bridge Assessment and Health Monitoring with Distributed Long-Gauge FBG Sensors  [PDF]
Chunfeng Wan,Wan Hong,Jianxun Liu,Zhishen Wu,Zhaodong Xu,Shu Li
International Journal of Distributed Sensor Networks , 2013, DOI: 10.1155/2013/494260
Abstract: Most sensors for structural testing and health monitoring are “point” sensors which strongly limit the ability to correct damage detection and structural assessment. In this paper, long-gauge FBG sensor which can sense the whole area within the gauge length is introduced. Bridge assessment and health monitoring with the microstrain distribution acquired by the distributed long-gauge FBG sensor are also studied. Experiments were conducted and application to a real prestressed box bridge was also implemented. Static and dynamic testing results show that distributed long-gage FBG sensing technique can obtain not only the global information such as bridge deflection and natural frequency, but also the local parameters such as strain and modal macrostrain to detect damage of the bridge. It shows that structural assessment and health monitoring based on the proposed technique have great potential in maintenance of civil engineering infrastructures. 1. Introduction Bridges are the most important facilities for many cities and countries. These infrastructures provide the necessary communication and transportation conditions for the residence. However, progressive deterioration of the civil infrastructure begins once they are built and subjected to normal continuous and occasional excessive loading, or adverse environmental conditions. For the purpose of protecting and maintaining these infrastructures, prompt and intensive monitoring of structural system becomes extremely important. Nowadays, most Structural Health Monitoring (SHM) research has focused either on global damage assessment techniques using structural dynamic responses or on limited local independent damage detection mechanisms. Vibration-based global SHM using typical acceleration measurements still faces some challenges for the reason that structural modal parameters seem too “global” to detect the damage that is an intrinsically local phenomenon in structures. On the other hand, although relatively reliable, local inspections are cost, labor-intensive, and too “local” to obtain the integrated information for the overall structure. Under this background, the concept of distributed long-gage FBG sensing techniques, which is dedicated to catching and utilizing the strain distribution throughout the full or some partial areas of structures to detect damage, has been proposed to develop an integrated SHM strategy [1]. As a typical local measurement, strain has been verified to be very sensitive to damage. However, for the health monitoring of large-scale civil structures, strain measurement always
Optical and Electric Multifunctional CMOS Image Sensors for On-Chip Biosensing Applications  [PDF]
Takashi Tokuda,Toshihiko Noda,Kiyotaka Sasagawa,Jun Ohta
Materials , 2011, DOI: 10.3390/ma4010084
Abstract: In this review, the concept, design, performance, and a functional demonstration of multifunctional complementary metal-oxide-semiconductor (CMOS) image sensors dedicated to on-chip biosensing applications are described. We developed a sensor architecture that allows flexible configuration of a sensing pixel array consisting of optical and electric sensing pixels, and designed multifunctional CMOS image sensors that can sense light intensity and electric potential or apply a voltage to an on-chip measurement target. We describe the sensors’ architecture on the basis of the type of electric measurement or imaging functionalities.
On the Displacement for Covering a $d-$dimensional Cube with Randomly Placed Sensors  [PDF]
Rafal Kapelko,Evangelos Kranakis
Computer Science , 2015,
Abstract: Consider $n$ sensors placed randomly and independently with the uniform distribution in a $d-$dimensional unit cube ($d\ge 2$). The sensors have identical sensing range equal to $r$, for some $r >0$. We are interested in moving the sensors from their initial positions to new positions so as to ensure that the $d-$dimensional unit cube is completely covered, i.e., every point in the $d-$dimensional cube is within the range of a sensor. If the $i$-th sensor is displaced a distance $d_i$, what is a displacement of minimum cost? As cost measure for the displacement of the team of sensors we consider the $a$-total movement defined as the sum $M_a:= \sum_{i=1}^n d_i^a$, for some constant $a>0$. We assume that $r$ and $n$ are chosen so as to allow full coverage of the $d-$dimensional unit cube and $a > 0$. The main contribution of the paper is to show the existence of a tradeoff between the $d-$dimensional cube, sensing radius and $a$-total movement. The main results can be summarized as follows for the case of the $d-$dimensional cube. If the $d-$dimensional cube sensing radius is $\frac{1}{2n^{1/d}}$ and $n=m^d$, for some $m\in N$, then we present an algorithm that uses $O\left(n^{1-\frac{a}{2d}}\right)$ total expected movement (see Algorithm 2 and Theorem 5). If the $d-$dimensional cube sensing radius is greater than $\frac{3^{3/d}}{(3^{1/d}-1)(3^{1/d}-1)}\frac{1}{2n^{1/d}}$ and $n$ is a natural number then the total expected movement is $O\left(n^{1-\frac{a}{2d}}\left(\frac{\ln n}{n}\right)^{\frac{a}{2d}}\right)$ (see Algorithm 3 and Theorem 7). In addition, we simulate Algorithm 2 and discuss the results of our simulations.
Random Deployment of Data Collectors for Serving Randomly-Located Sensors  [PDF]
Taesoo Kwon,John. M. Cioffi
Computer Science , 2011,
Abstract: Recently, wireless communication industries have begun to extend their services to machine-type communication devices as well as to user equipments. Such machine-type communication devices as meters and sensors need intermittent uplink resources to report measured or sensed data to their serving data collector. It is however hard to dedicate limited uplink resources to each of them. Thus, efficient service of a tremendous number of devices with low activities may consider simple random access as a solution. The data collectors receiving the measured data from many sensors simultaneously can successfully decode only signals with signal-to-interference-plus-noise-ratio (SINR) above a certain value. The main design issues for this environment become how many data collectors are needed, how much power sensor nodes transmit with, and how wireless channels affect the performance. This paper provides answers to those questions through a stochastic analysis based on a spatial point process and on simulations.
Estimation of Curvature Changes for Steel-Concrete Composite Bridge Using Fiber Bragg Grating Sensors  [PDF]
Donghoon Kang,Wonseok Chung
Advances in Materials Science and Engineering , 2013, DOI: 10.1155/2013/405143
Abstract: This study is focused on the verification of the key idea of a newly developed steel-concrete composite bridge. The key idea of the proposed bridge is to reduce the design moment by applying vertical prestressing force to steel girders, so that a moment distribution of a continuous span bridge is formed in a simple span bridge. For the verification of the key technology, curvature changes of the bridge should be monitored sequentially at every construction stage. A pair of multiplexed FBG sensor arrays is proposed in order to measure curvature changes in this study. They are embedded in a full-scale test bridge and measured local strains, which are finally converted to curvatures. From the result of curvature changes, it is successfully ensured that the key idea of the proposed bridge, expected theoretically, is viable. 1. Introduction A steel-concrete composite Rahmen bridge is one that the piers and girders are constructed as a monolithic structure. This type of bridge is widely constructed due to merits such as cost effectiveness in construction and maintenance, resistance in earthquake, and high quality in driving. A new structural system of steel-concrete composite Rahmen bridge is currently developed to increase the span length. The key technology of the new bridge is introducing a prestressing force to steel girders by applying vertical prestress to steel bars already embedded at the pier wall. By means of this technique, a moment distribution of a continuous span bridge is formed in a simple span bridge. This eventually reduces both the design moment of the bridge and the size of the bridge section. In order to verify the viability of the proposed key technology, it is necessary to evaluate the structural behavior of the bridge among construction stages. In general, concrete material should be cured at least 28 days to achieve the strength. The fabrication of a test bridge requires four major construction stages. Thus, in order to evaluate the expected behavior of the test bridge, curvature changes at four discrete construction stages are need to be monitored. However, since the proposed bridge system has sequential construction stages, long-term monitoring capability including absolute measurement and temperature compensation is important requirement of the sensing system for the test. Considering requirements necessary to the sensing system, fiber Bragg grating (FBG) sensors can be a good candidate because they can be easily applied to structures as multiplexed sensor arrays by embedment. FBG sensors have already been applied to many
Monolithic Pixel Sensors in Deep-Submicron SOI Technology with Analog and Digital Pixels  [PDF]
Marco Battaglia,Dario Bisello,Devis Contarato,Peter Denes,Piero Giubilato,Lindsay Glesener,Serena Mattiazzo,Chinh Vu
Physics , 2008, DOI: 10.1016/j.nima.2009.01.178
Abstract: This paper presents the design and test results of a prototype monolithic pixel sensor manufactured in deep-submicron fully-depleted Silicon-On-Insulator (SOI) CMOS technology. In the SOI technology, a thin layer of integrated electronics is insulated from a (high-resistivity) silicon substrate by a buried oxide. Vias etched through the oxide allow to contact the substrate from the electronics layer, so that pixel implants can be created and a reverse bias can be applied. The prototype chip, manufactured in OKI 0.15 micron SOI process, features both analog and digital pixels on a 10 micron pitch. Results of tests performed with infrared laser and 1.35 GeV electrons and a first assessment of the effect of ionising and non-ionising doses are discussed.
Radiation Tolerance of CMOS Monolithic Active Pixel Sensors with Self-Biased Pixels  [PDF]
M. Deveaux,S. Amar-Youcef,A. Besson,G. Claus,C. Colledani,M. Dorokhov,C. Dritsa,W. Dulinski,I. Froehlich,M. Goffe,D. Grandjean,S. Heini,A. Himmi,C. Hu,K. Jaaskelainen,C. Muentz,A. Shabetai,J. Stroth,M. Szelezniak,I. Valin,M. Winter
Physics , 2009, DOI: 10.1016/j.nima.2010.04.045
Abstract: CMOS Monolithic Active Pixel Sensors (MAPS) are proposed as a technology for various vertex detectors in nuclear and particle physics. We discuss the mechanisms of ionizing radiation damage on MAPS hosting the the dead time free, so-called self bias pixel. Moreover, we discuss radiation hardened sensor designs which allow operating detectors after exposing them to irradiation doses above 1 Mrad
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.