Beacon System Research Articles

Quencher-free molecular beacon systems with two pyrene units in the stem region

We appended pyrene units covalently onto adenosine and uridine nucleosides (forming A P and U P units, respectively) and then incorporated them into oligonucleotides such that they were positioned in complementary locations in opposite strands in the middle positions of hairpin stems. Systems 1 ( A P U P ) and 3 ( A P A P ) individually exhibit aromatic stacking between the opposing pyrene units in the stems of their hairpins and display in their spectra the photophysical properties of strongly red-shifted bands; in contrast, the U P U P system 2 exhibits quenching spectra. Systems 1 ( A P U P ) and 3 ( A P A P ) behave as effective molecular beacons (MBs) that change color from green to blue upon duplex formation, whereas 2 ( U P U P ) is an effective MB that changes the intensity of its fluorescence upon forming its perfectly matched duplex.

The Development of a Passive Microbial Fuel Cell Powered Small Marine Beacon System

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DYNAMIC LOCALIZATION OF A MOBILE ROBOT WITH ACTIVE BEACON SENSORS

With the development of service robots and with the emerging concept of ubiquitous world, localization of a mobile robot has become a popular issue. Even though several localization schemes are introduced previously, none of them is free from the economical constraints to be used for commercial robots. To implement a real time commercial localization system, a new absolute position estimation method for a mobile robot in indoor environment is proposed in this paper. Design and implementation of the localization system comes from the usage of active beacon systems each of which is composed of an RFID receiver and an ultra-sonic transmitter. The RFID receiver gets the synchronization signal from the mobile robot and the ultrasonic transmitter sends out a short-term signal to be used for measuring the distance from the beacon to the mobile robot. Position of a mobile robot in a three dimensional space can be calculated basically from the distance information from three beacons which have their own absolute position information. One of the interesting problems comes from the static localization scheme. That is, the collision avoidance against surrounding objects can be planned and controlled efficiently if the velocity of the moving object can be estimated. Main contribution of this paper is developing a dynamic localization scheme to be used for the moving objects, which is a new application field of active beacon sensors. In the dynamic localization scheme, sensor fusion techniques and extended Kalman filter have been used to improve the estimation accuracy. Experimental results demonstrate the effectiveness and feasibility of this scheme.

RFID 응용 기술을 이용한 이동 로봇의 실내 위치 추정

Recently, with the development of service robots and with the new concept of ubiquitous world, the position estimation of mobile objects has been raised to an important problem. As pre-liminary research results, some of the localization schemes are introduced, which provide the relative location of the moving objects subjected to accumulated errors. To implement a real time localization system, a new absolute position estimation method for a mobile robot in indoor environment is proposed in this paper. Design and implementation of the localization system comes from the usage of active beacon systems (based upon RFID technology). The active beacon system is composed of an RFID receiver and an ultra-sonic transmitter: 1. The RFID receiver gets the synchronization signal from the mobile robot and 2. The ultra-sonic transmitter sends out the traveling signal to be used for measuring the distance. Position of a mobile robot in a three dimensional space can be calculated basically from the distance information from. Three beacons and the absolute position information of the beacons themselves. In some case, the mobile robot can get the ultrasonic signals from only one or two beacons, because of the obstacles located along the moving path. Therefore, in this paper, as one of our dedicated contribution, the position estimation scheme with less than three sensors has been developed. Also, the extended Kalman filter algorithm is applied for the improvement of position estimation accuracy of the mobile robot.

First Tests of Wavefront Sensing with a Constellation of Laser Guide Beacons

Adaptive optics to correct current telescopes over wide fields, or even to correct future very large telescopes over narrow fields, will require real-time wavefront measurements made with a constellation of laser beacons. Here we report the first such measurements, made at the 6.5 m MMT with five Rayleigh beacons in a 2' pentagon. Each beacon is made with a pulsed beam at 532 nm of 4 W at the exit pupil of the projector. The return is range-gated from 20 to 29 km and recorded at 53 Hz by a 36-element Shack-Hartmann sensor. Wavefronts derived from the beacons are compared with simultaneous wavefronts obtained for individual natural stars within or near the constellation. Observations were made in seeing averaging 10 with two-thirds of the aberration measured to be from a ground layer of mean height 380 m. Under these conditions, subtraction of the simple instantaneous average of the five beacon wavefronts from the stellar wavefronts yielded a 40% rms reduction in the measured modes of the distortion over a 2' field. We discuss the use of multiple Rayleigh beacons as an alternative to single sodium beacons on 8 m telescopes and the impact of the new work on the design of a multi-sodium beacon system for the 25 m Giant Magellan Telescope.

Procedural and Operational Consequences of Navigational Equipment Outages: Exploration of Airport Performance

This paper explores the impact of unscheduled navigational and surveillance equipment outages on airport performance during visual flight rules and instrument flight rules at San Francisco International Airport and Phoenix Sky Harbor International Airport. The following most common unscheduled short outages, which occurred during January 2000-December 2002, are analyzed in detail: very high frequency omnidirectional range (VOR), approach lighting system type 2 (ALSF-2), the secondary radar Mode S, and air traffic control radio beacon system (ATCRBS). We explore the air traffic control procedures and responses to unscheduled outages, and develop a methodology to examine the effects of unscheduled outages on airport performance. Two Federal Aviation Administration databases, maintenance management system and aviation system performance metrics, are used to construct censored regression models (i.e., Tobit models) to assess the airport throughput performance during such unscheduled outages. It is found that airport arrival and departure throughputs do not deteriorate with VOR and ALSF-2 outages due to availability of air traffic procedures that allow alternative approaches into the airport. However, the unscheduled outages of secondary radar Mode S and ATCRBS do cause airport throughput degradations.

PEGASUS—Performance Experiments in Germany on ADS-B Using Mode S Extended Squitter

Future surveillance systems have to be capable of operating worldwide and to co-exist with other systems in the same frequency band. Extended Squitter is an ADS-B system which uses the same frequencies as current SSR (Secondary Surveillance Radar) systems (also called ATCRBS = Air Traffic Control Radar Beacon System). The German CAA, Deutsche Flugsicherung GmbH (DFS), and the U.S. Department of Transportation/Federal Aviation Administration (FAA) agreed to collaborate on a measurement activity in 2000 using Extended Squitter as the ADS-B medium. The Extended Squitter frequency 1090 MHz is actively being used for replies to secondary surveillance radars and for TCAS air-to-air surveillance. Frankfurt was chosen to perform the measurements under high interference conditions.The primary objective of the tests was the Extended Squitter performance measurement in the dense interference environment of Frankfurt. Both air-to-air and air-to-ground receptions were to be tested. For a good understanding of the results and to allow estimates for future environments, measuring the interference environment, the aircraft density and distribution was another objective. Results of these background measurements as well as of Extended Squitter performance in this specific environment are presented below.

Development of a New Reporter Gene System—dsRed/Xanthine Phosphoribosyltransferase-Xanthine for Molecular Imaging of Processes Behind the Intact Blood-Brain Barrier

We report the development of a novel dual-modality fusion reporter gene system consisting of Escherichia coli xanthine phosphoribosyltransferase (XPRT) for nuclear imaging with radiolabeled xanthine and Discosoma red fluorescent protein for optical fluorescent imaging applications. The dsRed/XPRT fusion gene was successfully created and stably transduced into RG2 glioma cells, and both reporters were shown to be functional. The level of dsRed fluorescence directly correlated with XPRT enzymatic activity as measured by ribophosphorylation of [14C]-xanthine was in vitro (Ki = 0.124 +/- 0.008 vs. 0.00031 +/- 0.00005 mL/min/g in parental cell line), and [*]-xanthine octanol/water partition coefficient was 0.20 at pH = 7.4 (logP = -0.69), meeting requirements for the blood-brain barrier (BBB) penetrating tracer. In the in vivo experiment, the concentration of [14C]-xanthine in the normal brain varied from 0.20 to 0.16 + 0.05% dose/g under 0.87 + 0.24% dose/g plasma radiotracer concentration. The accumulation in vivo in the transfected flank tumor was to 2.4 +/- 0.3% dose/g, compared to 0.78 +/- 0.02% dose/g and 0.64 +/- 0.05% dose/g in the control flank tumors and intact muscle, respectively. [14C]-Xanthine appeared to be capable of specific accumulation in the transfected infiltrative brain tumor (RG2-dsRed/XPRT), which corresponded to the 585 nm fluorescent signal obtained from the adjacent cryosections. The images of endogenous gene expression with the "sensory system" have to be normalized for the transfection efficiency based on the "beacon system" image data. Such an approach requires two different "reporter genes" and two different "reporter substrates." Therefore, the novel dsRed/XPRT fusion gene can be used as a multimodality reporter system in the biological applications requiring two independent reporter genes, including the cells located behind the BBB.

Development of a new reporter gene system--dsRed/xanthine phosphoribosyltransferase-xanthine for molecular imaging of processes behind the intact blood-brain barrier.

We report the development of a novel dual-modality fusion reporter gene system consisting of Escherichia coli xanthine phosphoribosyltransferase (XPRT) for nuclear imaging with radiolabeled xanthine and Discosoma red fluorescent protein for optical fluorescent imaging applications. The dsRed/XPRT fusion gene was successfully created and stably transduced into RG2 glioma cells, and both reporters were shown to be functional. The level of dsRed fluorescence directly correlated with XPRT enzymatic activity as measured by ribophosphorylation of [14C]-xanthine was in vitro (Ki = 0.124 +/- 0.008 vs. 0.00031 +/- 0.00005 mL/min/g in parental cell line), and [*]-xanthine octanol/water partition coefficient was 0.20 at pH = 7.4 (logP = -0.69), meeting requirements for the blood-brain barrier (BBB) penetrating tracer. In the in vivo experiment, the concentration of [14C]-xanthine in the normal brain varied from 0.20 to 0.16 + 0.05% dose/g under 0.87 + 0.24% dose/g plasma radiotracer concentration. The accumulation in vivo in the transfected flank tumor was to 2.4 +/- 0.3% dose/g, compared to 0.78 +/- 0.02% dose/g and 0.64 +/- 0.05% dose/g in the control flank tumors and intact muscle, respectively. [14C]-Xanthine appeared to be capable of specific accumulation in the transfected infiltrative brain tumor (RG2-dsRed/XPRT), which corresponded to the 585 nm fluorescent signal obtained from the adjacent cryosections. The images of endogenous gene expression with the "sensory system" have to be normalized for the transfection efficiency based on the "beacon system" image data. Such an approach requires two different "reporter genes" and two different "reporter substrates." Therefore, the novel dsRed/XPRT fusion gene can be used as a multimodality reporter system in the biological applications requiring two independent reporter genes, including the cells located behind the BBB.

Mars navigation system utilizes GPS

Tasks envisioned for future generation Mars rovers - sample collection, area survey, resource mining, habitat construction, etc. - will require greatly enhanced navigational capabilities over those possessed by the Mars Sojourner rover. Many of these tasks will involve cooperative efforts by multiple rovers and other agents, adding further requirements both for accuracy and commonality between users. This paper presents a new navigation system a Self-Calibrating Pseudolite Array (SCPA) that can provide centimeter-level, drift-free localization to multiple rovers within a local area by utilizing GPS-based transceivers deployed in a ground-based array. Such a system of localized beacons can replace or augment a system based on orbiting satellite transmitters, and is capable of fully autonomous operations and calibration. This paper describes the prototype SCPA developed at Stanford to demonstrate these capabilities and then presents results from a set of field trials performed at NASA Ames Research Center. These experiments, which utilize the K9 Mars rover research platform, validate both the navigation and self-calibration capabilities of the system. By carrying an on-board GPS transceiver, K9 was successfully able to calibrate the system using no a priori position information and localized the pseudolite beacons to under 5 cm RMS.

Positioning beacon system using digital camera and leds

This paper is on a novel use of lighting or signaling devices constructed by light-emitting diodes (LEDs) as a positioning beacon. The idea is that the surface of the LED lighting device is divided into regions and used to show different visual patterns that are not noticeable by the human eye due to the high-frequency switching of the LEDs. A digital camera is used as a receiver to capture a sequence of images of the LED positioning beacon transmitter. Image-processing algorithms are used to decode the location code that is encoded in the visual patterns transmitted by the LED device. This idea can be applied to any LED traffic lights or signaling devices on the road and turn them into parts of a positioning beacon system. Such a system made up of high-brightness visible LEDs can provide the function of open-space wireless broadcasting of the positioning signal. The LED signaling method, transmission protocol, camera frame rate, LED flash rate, together with an implemented system and the experimental results, are presented in this paper.

A Local-Area GPS Pseudolite-Based Navigation System for Mars Rovers

Tasks envisioned for future generation Mars rovers—sample collection, area survey, resource mining, habitat construction, etc.—will require greatly enhanced navigational capabilities over those possessed by the Mars Sojourner rover. Many of these tasks will involve cooperative efforts by multiple rovers and other agents, adding further requirements both for accuracy and commonality between users. This paper presents a new navigation system called a Self-Calibrating Pseudolite Array (SCPA) that can provide centimeter-level, drift-free localization to multiple rovers within a local area by utilizing GPS-based transceivers deployed in a ground-based array. Such a system of localized beacons can replace or augment a system based on orbiting satellite transmitters, and is capable of fully autonomous operations and calibration. This paper describes the basic principles of navigation using an SCPA, focusing on the critical issue of array self-calibration. The new algorithm presented herein—called Quadratic Iterative Least Squares—achieves successful self-calibration 99.80% of the time even under extremely adverse conditions. The paper concludes with a description of the experimental prototype developed to demonstrate these capabilities and presents successful results from field trials which validate both the navigation and self-calibration functions of the SCPA.

Positioning beacon system using digital camera and LEDs

This paper is on a novel use of lighting or signaling devices constructed by light-emitting diodes (LEDs) as a positioning beacon. The idea is that the surface of the LED lighting device is divided into regions and used to show different visual patterns that are not noticeable by the human eye due to the high-frequency switching of the LEDs. A digital camera is used as a receiver to capture a sequence of images of the LED positioning beacon transmitter. Image-processing algorithms are used to decode the location code that is encoded in the visual patterns transmitted by the LED device. This idea can be applied to any LED traffic lights or signaling devices on the road and turn them into parts of a positioning beacon system. Such a system made up of high-brightness visible LEDs can provide the function of open-space wireless broadcasting of the positioning signal. The LED signaling method, transmission protocol, camera frame rate, LED flash rate, together with an implemented system and the experimental results, are presented in this paper.

LED location beacon system based on processing of digital images

This paper is in the field of vehicle positioning technology for the intelligent transportation systems. The ideas of an innovative light-emitting diode (LED)-based location beacon system are developed and verified. The system developed is a combination of several latest technologies which include a CMOS vision sensor, high brightness LED, and digital image processing techniques. It belongs to a new kind of simplex communication link. A digital camera is used to capture images contained in the LED beacon signal. The captured digital images are processed by the algorithms developed and a location code is extracted. The location code can be used for calibration of a vehicle positioning system which may consist of a GPS, inertial navigation system (INS) and other sensors. The issues examined include the structure of the transmitter and the receiver, the signaling method, the transmission protocol of the LED panel, the relationship between the camera capturing rate and the LED pattern update rate, the digital camera exposure technology, and the efficiency of the image processing algorithms. Experiments using a prototype transmitter and a receiver were performed. The experimental results provide a good demonstration of the viability of the ideas and methodologies developed.

Modeling Motorway Driving Behavior

Microscopic traffic simulation constitutes a useful method for predicting the effects of new transport telematic systems on road traffic. In such a simulation, the driver model is a key element describing the dynamic individual driving behavior in relation to the vehicle, the road environment, and other traffic participants. The driver model presented in this paper was developed partly on the basis of literature and partly on the author’s own experimental research with a driving simulator and an instrumented vehicle. The driver model includes free driving (speed control), car following (distance control), and lane-change behavior. It interacts with a vehicle model at a detailed level (pedals and gear status). The driver model uses the vehicle controls with the aim to reach or maintain the individual, situation-dependent desired speed or following distance. The model includes aspects such as reaction time, perception thresholds for speed differences, and comfort levels for accelerating and decelerating. Since the traffic simulation model was designed to study the effects of systems such as adaptive cruise control (ACC), the driver model also includes a component that describes the driver’s interaction with ACC. In addition to a description of the model and its background, an illustration of the model’s application is given in a case study on ACC, where the ACC’s reference speed was influenced externally by a modeled beacon system. In conditions with high traffic volumes, the beacon system influenced the traffic upstream to try to create a homogeneous, steady traffic flow.

Diffractive optics for compact space communication terminals

Abstract Free-space laser communication links with data rates between 10 and 500 Mbits s−1 are required to cover the large amount of communication needs between low-orbit satellites, geostationary satellites and ground stations. The objective of this paper is to demonstrate the potential of diffactive optical elements for the design of optical and optoelectronic systems for advanced laser communication terminals. Three different examples have been realized: a ring pattern generator, an athermalized and achromatic hybrid collimator system, and a hybrid beacon system.

Altitude prediction by natural spline tracker

AbstractIn airborne collision avoidance system (ACAS) and air traffic control radar beacon system, altitude tracking filter is used for altitude prediction. These trackers are known to have large error when the data are lost. This paper presents the new prediction filter to improve the accuracy in this coast situation. the extrapolation of natural spline function is used for this purpose. the simulation shows this tracking filter has better performance than conventional filter.

A Stochastic Analysis of State Transitions in an Air-Space Management System

This paper explores the application of stochastic process ideas to answer some fundamental questions about a state system which arises in the Mode Select Beacon System (Mode-S), an air-space management system. A series of models is developed, based on semi-Markov processes, population models, and Monte Carlo simulation. Computer programs in the APL programming language to implement the models and to process the resulting data are developed. The output of the models illuminate the behavior of the state system by providing predictions with confidence bounds about the movements of aircraft among the states over time.

4951263 Spread spectrum underwater location beacon system

4951263 Spread spectrum underwater location beacon system

Generation and properties off synthetic aperture polar diagrams for use in df systems

A synthetic aperture method of generating polar diagrams with shapes which conform to Bessel functions rather than the more familiar sin x/x form is described. The method can be used to generate, using a circular array, polar diagrams for use in Doppler DF and VOR beacon systems. This generation avoids the amplitude limiting employed in conventional forms of these systems. The method is applicable to linear arrays and can be used in microwave landing aids. In this application, a very good side lobe performance superior to the (sin x)/x form is obtainable. The site error suppression performance of a Doppler DF having a synthetic aperture is compared with a conventional Doppler system. Both are compared with a standard based on utilisation of a (sin x)/x lobe structure. No practical work on a DF system has been undertaken, although the generation has been used in another project; some measured results are given in this respect. The main conclusion is that the generation will enable the Doppler DF concept to eliminate the disadvantage of being prone to considerable inaccuracies, as caused by abnormally strong reflections. >