» Reference Papers

Closed-Form Underwater Acoustic Direction-Finding with Arbitrarily Spaced Vector Hydrophones at Unknown Locations

arjun — Mon, 10 Nov 2008 19:06:55 +0000

Abstract This paper introduces a novel ESPRIT-based closed form source localization algorithm applicable to arbitrarily spaced three-dimensional arrays of vector hydrophones, whose locations need not be known. Each vector hydrophone consists of two or three identical but orthogonally oriented velocity hydrophones plus one pressure hydrophone, all spatially co-located in a point-like geometry. A velocity hydrophone measures one Cartesian component of the incident sonar wavefield’s velocity vector, whereas a pressure hydrophone measures the acoustic wavefield’s pressure. Velocity-hydrophone technology is well established in underwater acoustics and a great variety of commercial models have long been available. ESPRIT is realized herein by exploiting the nonspatial interrelations among read more

A New Multilayer Planar PVDF Standard Hydrophone and its Applications

arjun — Mon, 10 Nov 2008 18:53:41 +0000

Abstract A new type of PVDF hydrophone, the multilayer planar PVDF hydrophone, is described in this paper. The hydrophone disturbs measured acoustic fields very little and has a high sensitivity. The noise equivalent pressure of the hydrophone is 45 dB re 1 μ Pa per Hz bandwidth.The working freqency range og hyrophon is 20kHz ~4MHz.In the range of 100kHz ~ 1MH,the hydrophone has a flat frequency response with sensitivity -205 dB & 1.5 dB (0 dB = 1 V/pPa). In this range, the hydrophone has been used for five years as a standard one. Two other applications (measurements of noise spectra and ultrasonic imaging) are also reported. Download Share and Enjoy: read more

DEVELOPMENT OF A COST-EFFECTIVE SHOCK WAVE HYDROPHONE

arjun — Mon, 10 Nov 2008 18:43:38 +0000

Abstract The design of a new wideband, quantitative shock wave hydrophone is presented. The sensor not only has a wideband (>SOMHz) and linear (up to 100MPa) response, but it also operates in a measurement environment in which the hydrophone element’s sensitivity changes as a function of shock wave exposure. Thin films of polyvinylidene difluoride (PVDF) were used in a disposable hydrophone configuration. A self-monitoring feature, based on the change in hydrophone electrode resistance as the electrode materials are removed by shock wave action, indicates that the hydrophone element needs to be replaced. Development efforts include: 1) reducing the manufacturing costs; 2) determining the relationship between electrode resistance and hydrophone sensitivity; 3) developing a read more

SoC Issues for RF Smart Dust

arjun — Mon, 10 Nov 2008 18:15:29 +0000

Abstract Wireless sensor nodes are autonomous devices incorporating sensing, power, computation, and communication into one system. Applications for large scale networks of these nodes are presented in the context of their impact on the hardware design. The demand for low unit cost and multiyear lifetimes, combined with progress in CMOS and MEMS processing, are driving development of SoC solutions for sensor nodes at the cubic centimeter scale with a minimum number of offchip components. Here, the feasibility of a complete, cubic millimeter scale, single-chip sensor node is explored by examining practical limits on process integration and energetic cost of short-range RF communication. Autonomous cubic millimeter nodes appear within reach, but process complexity and substantial read more

On the Optimal Number of Smart Dust Particles

arjun — Mon, 10 Nov 2008 18:11:35 +0000

Abstract Smart Dust particles are small smart materials used for generating weather maps. We investigate the open problem posed by Vidal et al. on the optimal number of Smart Dust particles necessary for constructing,precise.,cost effective and accurate 3-D weather map. Keywords: Smart structures,matching ,optimization Download Share and Enjoy: read more

Smart dust: Monte Carlo simulation of self-organised transport

arjun — Mon, 10 Nov 2008 18:04:02 +0000

Abstract Smart dust has been conceived as millimeter scale autonomous systems that form the basis for massively distributed wireless sensor networks[ 1, 21. Smart dust motes have been demonstrated that pack sensors, interfaces, power sources, digital control communications and processing circuitry into a few cubic millimeters volume. Previously, both the delivery of a mote swarm and communicating with such systems has been studied. Here we address the problem of how to subsequently move dust motes around in their application environment. Solutions involving robot insect motes have been advocated where distances and times are small; but this introduces additional mechanical and electronic complexity plus severe constraints on power sources. Instead, we focus on the possibility of read more

SIZING UP SMART DUST

arjun — Mon, 10 Nov 2008 18:00:41 +0000

Abstract THE NAME STARTED OUT AS SOMETHING OF A JOKE. “EVERYONE WAS TALKING ABOUT SMART HOUSES, SMART BUILDINGS, SMART BOMBS, AND I THOUGHT THAT IT WAS funny to talk about smart dust,” remembers Kris Pister. Though he might have named his invention partly in jest, “smart dust” is now part of the technical lexicon. The tiny, wireless sensors that started out in his University of California, Berkeley, office can now be found in laboratories around the country, where scientists and engineers across many disciplines are eagerly devising applications for them. With possible uses in the military, the home, and the environment— and a new commercial company (Dust, Inc.) devoted solely to its development—today more than ever, smart dust is no joke. How Pister’s company came to be, read more

A Sleep-Awake Protocol for Information Propagation in Smart Dust Networks

arjun — Mon, 10 Nov 2008 17:56:00 +0000

Abstract Smart Dust is a set of a vast number of ultra-small fully autonomous computing and communication devices, with very restricted energy and computing capabilities, that co-operate to quickly and efficiently accomplish a large sensing task. Smart Dust can be very useful in practice i.e. in the local detection of a remote crucial event and the propagation of data reporting its realization. In this work we continue (see [4]) our effort towards the research on smart dust from a basic algorithmic point of view. Under a simple but realistic model for smart dust we present an interesting problem, which is how to propagate efficiently information on an event detected locally. Then we present a new smart dust protocol, which we call the “Sleep-Awake” protocol, for information read more

SMART DUST MOTE FORERUNNERS

arjun — Mon, 10 Nov 2008 17:51:58 +0000

Abstract We have demonstrated a 138mm3 autonomous uni-directional sensing/communication mote that optically transmits a measure of the ambient light level. We have also developed a 6 3 m 3 autonomous bi-directional communication mote that receives an optical signal, generates a pseudorandom sequence based on this signal to emulate sensor data, then optically transmits the result, although it has only been demonstrated in a bench configuration at this time. The latter system contains a micromachined comer cube reflector, a 0.078mm3 CMOS chip that consumes 75pW, and a Mn-Ti-Li cell, but we have also demonstrated operation from an -2mm2 solar cell. These motes allow us to demonstrate necessary concepts of Smart Dust such as optical data transmission, data processing, energy management, read more

Smart Dust:Communicating with a Cubic-Millimeter Computer

arjun — Mon, 10 Nov 2008 17:46:41 +0000

Abstract Decreasing computing device size, increased connectivity, and enhanced interaction with the physical world have characterized computing’s history. Recently, the popularity of small computing devices, such as handheld computers and cell phones, burgeoning Internet growth, and the diminishing size and cost of sensors— especially transistors—have accelerated these trends. The emergence of small computing elements, with sporadic connectivity and increased interaction with the environment, provides enriched opportunities to reshape interactions between people and computers and spur ubiquitous computing research. The Smart Dust project is exploring whether an autonomous sensing, computing, and communication system can be packed into a cubic-millimeter mote (a small particle or read more