Flexible electronics could find applications as sensors, artificial muscles. Flexible electronic structures with the potential to bend, expand and manipulate electronic devices are being developed by researchers at the U.S. Department of Energy's Argonne National Laboratory and the University of Illinois at Urbana-Champaign. These flexible structures could find useful applications as sensors and as electronic devices that can be integrated into artificial muscles or biological tissues. With the many resources at Argonne at his disposal, Sun plans to expand his research to focus on applications in other biological and chemical sensors. Funding for this research was provided by the U.S. Department of Energy's Office of Basic Energy Science. The nation's first national laboratory, Argonne National Laboratory conducts basic and applied scientific research across a wide spectrum of disciplines, ranging from high energy physics to climatology and biotechnology. Argonne has worked with numerous federal agencies and other organizations to help advance America's scientific leadership and prepare the nation for the future. Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.
In addition to a biomedical impact, flexible electronics are important for energy technology as flexible and accurate sensors for hydrogen.
These structures were developed from a concept created by Argonne scientist Yugang Sun and a team of researchers at the University of Illinois led by John A. Rogers. The concept focuses on forming single-crystalline semiconductor nanoribbons in stretchable geometrical configurations with emphasis on the materials and surface chemistries used in their fabrication and the mechanics of their response to applied strains.
Flexible electronics are typically characterized by conducting plastic-based liquids that can be printed onto thin, bendable surfaces
The team of researchers has been successful in fabricating thin ribbons of silicon and designing them to bend, stretch and compress like an accordion without losing their ability to function.
The Center for Nanoscale Materials at Argonne integrates nanoscale research with Argonne's existing capabilities in synchrotron X-ray studies, neutron-based materials research and electron microscopy with new capabilities in nanosynthesis, nanofabrication, nanomaterials characterization, and theory and simulation.
Instrument Landing System (ILS) is the international slandered for approach landing guidance . ILS was adopted by International Civil Aviation Organization (ICAO) in 1947 and will be in service until least 2005. The Instrument Landing System (ILS) provides a means for safe landing of aircraft at airports underconditions of low ceiling and limited visibility. The use of the system materially reduces interruptions of service at airports resulting from bad weather by allowing operations to continue at lower weather minimums. The ILS also increases the traffic handling capacity of the airport under all weather conditions.
The functions of an ILS is to provide the PILOT or AUTOPILOT of a landing aircraft with the
guidance to and along the surface of the runway. This guidance must be of very high integrity to ensure that each landing has a very high probability of success.
Components of ILS
The basically philosophy of ILS is that ground installations, located in the vicinity of the runway,
transmit coded signals in such a manner that pilot is given information indicating position of the
aircraft with respect to correct approach path.
To provide correct approach path information to the pilot, three different signals are required to be transmitted. The first signal gives the information to the pilot indicating the aircraft’s position relative to the centerline of the runway. The second signal gives the information indicating the aircraft’s position to the required angle of descent, where as the third signal provides distance information from some specified point.
Theses three parameters which are essential for a safe landing are Azimuth Approach Guidance and Range from the touch down point .These are provided to the pilot by three components of the ILS namely Localizer, Glide Path and Marker Beacons respectively. At some airports the Marker Beacons are replaced by a Distance Measuring Equipment (DME).
1 Localizer Unit
The localizer unit consists of an equipment building, the transmitter equipment, a platform, the
antennas, and field detectors. The antennas will be located about 1,000 feet from the stop end of the runway and the building about 300 feet to the side. The detectors are mounted on posts a short distance from the antennas.
2. Glide Path Unit
The Glide Path unit is made up of a building, the transmitter equipment, the radiating antennas and monitor antennas mounted on towers. The antennas and the building are located about 500 feet to one side of the runway centre line at a distance of approximately 1,000 feet from the approach end of the runway.
3. Marker Units
Three Marker Units are provided. Each Marker unit consists of a building, transmitter and directionalantenna array. The system will be located near the runway centre line, extended. The transmitters are 75 MHz, low power units with keyed tone modulation. The units are controlled via lines from thetower. The outer marker will be located between 4 and 7 miles in front of the approach end of the runway, so the pattern crosses the glide angle at the intercept altitude. The modulation will be 400 Hz keyed at 2 dashes per second.
The middle marker will be located about 3500 feet from the approach end of the runway, so the pattern interests the glide angle at 200 feet. The modulation will be a 1300 Hz toon keyed by continuous dot, dash pattern. Some ILS runways have an inner marker located about 1,000 feet from the approach end of therunway, so the pattern intersects the glide angle at 100 feet. The transmitter is modulated by a tone of3000 Hz keyed by continuous dots.
4. Distance Measuring Equipment (DME)
Where the provision of Marker Beacons is impracticable, a DME can installed co-located with the Glide Path facility.
5. Locater Beacons
The ILS should be supplemented by sources of guidance information which will provide effected
guidance to the desired course, Locator Beacons, which are essentially low power NDBs, installed at Outer Marker and middle Marker locations will serve this purpose.
6. Aircraft ILS Component
The Azimuth and Elevation guidance provided by the Localizer and Glide Path respectively to the pilot continuously by an on-board meter called the Cross Deviation Indicator (CDI).Range information isprovided continuously in the form of digital readout if DME is used with ILS. However range information is not visual indications of specific distances are provide by means of audio coded signals and lighting of appropriate coloured in the cockpit.
ILS Signal Format
Introduction
ILS employs amplitude modulation of a radio frequency carrier to provide the guidance information. The modulating signals used in ILS are pure sine waves of 90 Hz and 150 Hz frequency. This handout deals with the characteristics feathers of singles radiated by Localizer and Glide Path.
Principles of operation
An ILS consists of two independent sub-systems, one providing lateral guidance, the other vertical guidance to aircraft approaching a runway.
A localizer (LOC) antenna array is normally located beyond the departure end of the runway and generally consists of several pairs of directional antennas. Two signals are transmitted on a carrier frequency between 108 MHz and 111.975 MHz. One is modulated at 90 Hz, the other at 150 Hz and these are transmitted from separate but co-located aerials. Each aerial transmits a fairly narrow beam, one slightly to the left of the runway centreline, the other to the right. The localizer receiver on the aircraft measures the difference in the depth of modulation of the 90 Hz and 150 Hz signals, when this difference is zero the receiver aerial is on the centreline of the localizer which normally coincides with the runway centreline.
A glideslope (GS) antenna array is sited to one side of the runway touchdown zone. The GS signal is transmitted on a carrier frequency between 328.6 MHz and 335.4 MHz using a technique similar to that of the localizer, the centreline of the glideslope signal being arranged to define a glideslope at approximately 3° above the horizontal.
Localizer and glideslope carrier frequencies are paired so that only one selection is required to tune both receivers. Localizer and glideslope signals are displayed on a cockpit instrument, called a Course deviation indicator (CDI), as vertical and horizontal needles (or an electronic display simulating needles). The pilot controls the aircraft so that the needles remain centred on the display, the aircraft then follows the ILS centreline. The signals are also fed into autopilot systems to allow approaches to be flown on autopilot.
Radar measures the range and bearing of an aircraft. Bearing is measured by the position of the rotating radar antenna when it receives a response to its interrogation from the aircraft, and range is measured by the time it takes for the radar to receive the interrogation response. The antenna beam becomes wider as the aircraft gets further away, making the position information less accurate. Additionally, detecting changes in aircraft velocity requires several radar sweeps that are spaced several seconds apart. In contrast, a system using ADS-B creates and listens for periodic position and intent reports from aircraft. These reports are generated and distributed using precise instruments, such as the global positioning system (GPS) and Mode S transponders, meaning integrity of the data is no longer susceptible to the range of the aircraft or the length of time between radar sweeps. PSR is robust in the sense that surveillance outage failure modes are limited to those associated with the ground radar system. SSR failure modes include the transponder aboard the aircraft. Typical ADSB aircraft installations use the output of the navigation unit for navigation and cooperative surveillance, introducing a common failure mode that must be accommodated in air traffic surveillance systems
There are two commonly recognized types of ADS for aircraft applications:
· ADS-Addressed (ADS-A), also known as ADS-Contract (ADS-C), and · ADS-Broadcast (ADS-B). ADS-B is inherently different from ADS-A, in that ADS-A is based on a negotiated one-to-one peer relationship between an aircraft providing ADS information and a ground facility requiring receipt of ADS messages.
For example, ADS-A reports are employed in the Future Air Navigation System (FANS) using the Aircraft Communication Addressing and Reporting System (ACARS) as the communication protocol. During flight over areas without radar coverage (e.g., oceanic, polar), reports are periodically sent by an aircraft to the controlling air traffic region. ADS-B consists of three components:
· A transmitting subsystem that includes message generation and transmission functions at the source. · The propagation medium. · A receiving subsystem that includes message reception and report assembly functions at the receiving vehicle or ground system.
The source of the state vector and other transmitted information as well as user applications are not considered to be part of the ADS-B system.
Automatic Dependent Surveillance (ADS)
It came under Future Air Navigation System (FANS) introduced by ICAO (International Civil
Aviation Organization).It has overcome the difficulties faced by the conventional navigational aids and communication systems especially in oceanic regions where installation as well as maintenance of the conventional navigational aids and communication systems where difficult if not impossible. Moreover , since it uses mainly Satellite Communication,the usable range of the system is not restricted by the Radio Horizon.
Though introduced earlier,CPDLC (Controller Pilot Link Communication) is still very important & kept as part and parcel with ADS. Through this data-link,Air Traffic Controller(ATCO) can
communicate with the Pilot. It outcasts the conventional voice communication in the sense that in the latter,several types of noise,fading and inclusion of personal linguistic accent often make the messages unreadable.
Currently there is a divergence of government and industry positions concerning concepts,
applications, costs and benefits for automatic dependent surveillance broadcast (ADS-B) development, deployment and regulatory status. Most of the potential controversy exists because there is no integrated systems approach that addresses a direct benefits driven transition plan for ADS that enables transformation of the National Airspace System from a ground centric to an airborne centric system.
Description of ADS ground equipment
It comprises of a Local Area Network (LAN) with
1. Redundant Input/Output cum Database Servers (IOS) having separate disk storage system
for database and data required for replay of different events occurred over a time period.
2. A dedicated Terminal Work Station (TWS) through which the system communicates with
the outer world using PSTN (SITA) service provider and private WAN (AMSS) owned by
Airports Authority of India.
3. A few Workstations placed at different ATC user positions (TWR,MCD,A-W,A-E etc.)
and Air Force user position (MLU) for liaison purpose.
Data input/output to the ground station
1. ADS data through SITA (Society of International Telecommunication Aeronautical), from the
different aircrafts.
2. Flight Plan data from AMSS (Automatic Message Switching System).
Generation of ADS Data airborne ADS Equipment
Different flight data prepared by the Flight Management Computer (FMC) of the Aircraft (viz. Call Sign, Co-ordinate in terms of latitude and longitude, Altitude, Azimuth i.e angular position with respect to the magnetic north , speed etc) are sent to the Ground Station by the aircraft airborne ADS equipment when data link with link with ground station is established.
Flight Plan
Before a flight starts, the details of the Air-Route to be followed including many other information needed for safe navigation is prepared and delivered to the pilot. This is called Flight-Plan.Flight plans are plans filed by pilots with the local Aviation Authority (e.g. FAA in the USA) prior toflying. They generally include basic information such as departure and arrival points, estimated time,alternate airports in case of bad weather, type of flight whether instrument flight rules or visual flightrules, pilot's name and number of passengers. Flight plans are required for flights under IFR. UnderVFR, they provide a way of alerting rescuers if the flight is overdue.
Process of using ADS/CPDLC
As a beginning , the pilot initiates a ' Log On' procedure which established the link with the ground station with consent of ATCO. When the aircraft is 'connected' to the ground station, ATCO configures his configures his computer for downloading the selected flight data from the aircraft, periodically at a selected interval. This constitutes ADS Data.
In this process , an embedded but separately recognized CPDLC link is also initialized by ATCO.
Through this link pilot and ATCO can exchange required messages mostly of pre-formatted type. The message appear in the screens at both the ends.
Displaying of dynamic situation information of the aircrafts in front of ATCO
ADS data and flight plan data received by TWS is sent to IOS. The relevant software present in IOS and other workstation process those data and make a central data storage at IOS . Using ADS software at some dedicated user positions (ADS & MNT) the positional situation of the aircrafts are displayed on a separate 29 inch color monitor dynamically , in the form of 'blips' like that of a RADAR screen.
These blips show the actual positions of the aircrafts.
1. Video maps of the relevant air-routes with positions of Aeronautical Fixes and positions of
different Nav-aids on them , Flight Information Region (FIR) , geographic
territories/boundaries etc. are super imposed on the display . The aircraft 'blips' also
accompany a data block which displays some selectable parameters of the aircrafts (viz.Call
Sign , azimuth, altitude etc.). since the ADS uses Satellite Communication , there is no bar of any range. Surveillance over a far bigger chunk of earth, including oceanic regions becomes easier of ATCO
Associated Hardware and Software
Servers and workstations use SPARC Processors from Sun Microsystems Inc.
All the Hard disks/Tape drive used are SCSI type.
Operating System used in SUN OS version 5.4
LAN established is in star topology , use 100 MBPS Ethernet switches.
Applications are provided by Electronics Corporation of India Ltd.
The wireless world has technologically swept the world by its feet is a conclusion, but enterprises are still trying out which unwired segment would finally make it as the true heir of seamless connectivity- WiMAX or WiFi. In the last couple of years, Indian enterprise have been toying with wireless networking or community called WiFi technology after invoking the 802.11 a , b and g standards specified by IEEE body. Alternatively, WiMAX , a novice wireless technology is competing with WiFi in its bid to be recognized as the default network among enterprises.
USE AND HOW WIFI WORKS
Wi-Fi™ networks use radio technologies called IEEE 802.11 to provide secure, reliable, fast
wireless connectivity. A typical Wi-Fi setup contains one or more Access Points (APs) and one
or more clients. An AP broadcasts its SSID (Service Set Identifier, "Network name") via
packets that are called beacons, which are usually broadcast every 100 ms. The beacons are
transmitted at 1 Mbit/s, and are of relatively short duration and therefore do not have a
significant effect on performance. Since 1 Mbit/s is the lowest rate of Wi-Fi™ it assures that the
client that receives the beacon can communicate at at least 1 Mbit/s. Based on the settings (e.g.
the SSID), the client may decide whether to connect to an AP. If two APs of the same SSID are
in range of the client, the client firmware might use signal strength to decide with which of the
two APs to make a connection.
A Wi-Fi™ network can be used to connect computers to each other to the internet and to wired
networks (which use IEEE 802.3 or Ethernet). Wi-Fi™ networks operate in the unlicensed 2.4
(802.11b/g) and 5 GHz (802.11a/h) radio bands, with an 11 Mbit/s (802.11b) or 54 Mbit/s
(802.11a or g) data rate or with products that contain
both bands (dual band). They can provide
real world performance similar to the basic 10BaseT wired Ethernet networks.
PROBLEMS WITH WIFI
The main problem with wifi is power consumption. According to New York –based ABI research, high power consumption is one of the main issues that hamper widespread WiFi adoption.
The second one is security problem. In 2001,security lapses were indentified in 802.11 Wired Equivalent of Privacy (WEP) – a security mechanism defined by original 802.11 IEEE standard. In fact, telecom major AT&T admitted that they were hit by a slew of hackers who gained unauthorized access into their wireless networks.
Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g with
a stock antenna might have a range of 45 m (150 ft) indoors and 90 m (300 ft) outdoors. Range
also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range
than Wi-Fi in the 5 GHz frequency block. Outdoor range with improved (directional) antennas
can be several kilometres or more with line-of-sight.
Wi-Fi pollution, or an excessive number of access points in the area, especially on the same or
neighboring channel, can prevent access and interfere with the use of other access points by
others, caused by overlapping channels in the 802.11g/b spectrum, as well as with decreased
signal-to-noise ratio (SNR) between access points. This can be a problem in high-density areas,
such as large apartment complexes or office buildings with many Wi-Fi access points.
Additionally, other devices use the 2.4 GHz band: microwave ovens, cordless phones, baby
monitors, security cameras, and Bluetooth devices can cause significant additional interference.
WHAT NEXT?? THINK ABOUT WIMAX
As per industry sources, many vendors are working on all aspects of securing and transforming wireless technology. The products that are being built today are provisioned in such a manner that they support both WiFi and WiMAX technologies.
Today, with increasing bandwidth-intensive application and data overloaded, most enterprises plan to opt for this wireless technologies so that they are able to distribute broadband bandwidth.
Analysts point out that the choice in adopting technologies like WiFi or WiMAX by enterprises will depend on the need for higher bandwidth and increasing connectivity speed. People would use WiFi in their offices and WiMAX when they are mobile.
Incidentally, technology users had earlier complained that WiFi didn’t support bandwidth-hungry features like video conferencing. Also at times QoS for conferencing was poor.
So for hing bandwidth WiFi is replaced by WiMAX.
Now, question: which is economical?
Installation and vendor equipments costs for WiFi are relatively economical than WiMAX.
While the cost of deployment of a subscriber station for WiFi connectivity varies from $150 to $250, a WiMAX base station deployment would cost around $25,000 to $30,000.
According to analysts, WiFi would operate in an unlicensed spectrum, while WiMAX would require a licensed spectrum.
However, I think service provider opting for a WiMAX license makes business sense, as they are in a better position to handle the initial cost involved in deplument.
So what would you opt for? More secure , highly bandwidth WiMAX or cost-effective WiFi?