Two recent announcements, from Sandia Labs and car maker BMW, have suggested that lasers could ultimately provide a more-efficient alternative to LEDs in certain lighting applications. Sandia conducted experiments to evaluate whether a four-color laser system could provide a viable white-light illumination source. Meanwhile, BMW has demonstrated a prototype laser-based headlight system on its i8 Concept car that uses blue lasers and phosphors.
The Sandia experiment combined the output of four laser colors – blue, red, green and yellow – to create a white light source that was compared with other light sources, including incandescent and LED-based sources. The results were reported in the OSA’s Optics Express journal.
Intuitively, one would not expect that lasers would be an ideal light source. One reason is the extremely narrow spot size: imagine trying to illuminate a kitchen surface with a white version of a laser pointer. Obviously, this can be addressed with a suitable optical system. The same applies to optical safety issues caused by the intense laser beams.
Another factor is the extremely narrow linewidth of the laser sources. Four very narrow peaks at red, blue, green and yellow wavelengths would not be expected to result in good color rendering, compared to much broader peaks from LED sources, or the continuous spectrum of sunlight.
“Before these tests, our research in this direction was stopped before it could get started,” said Sandia researcher Jeff Tsao, who proposed the comparative experiment. “The typical response was, ‘Are you kidding? The color rendering quality of white light produced by diode lasers would be terrible.’ So finally it seemed like, in order to go further, one really had to answer this very basic question first.”
Sandia’s experiment asked volunteers to state their preference for objects illuminated by different light sources. The laser-based approach fared quite well, and was certainly not terrible. “What we showed is that diode lasers are a worthy path to pursue for lighting,” said Tsao.
More specifically, there was a statistically significant preference for the diode-laser-based white light over the warm and cool LED-based white light, but no statistically significant preference between the diode-laser-based and either the neutral LED-based or incandescent white light.
The results don’t go much beyond suggesting that lasers shouldn’t be ruled out as a potential illumination source. There is no immediate threat to LED-based lighting from a four-laser system, since the performance of different-colored laser diodes varies widely. In a Sandia press release, Tsao suggested that blue and red diode lasers might be used in combination with yellow and green LEDs.
Showing posts with label the impetus. Show all posts
Showing posts with label the impetus. Show all posts
Wednesday, 2 November 2011
Monday, 31 October 2011
Bike lights could save your life
POLICE hope these photos will show the danger of cycling without lights before they launch another crackdown.
Officers will be stopping riders in Bournemouth this autumn and issuing 30 fines, which are cancelled if offenders buy lights within seven days.
In the first photo, the rider has no night-time gear and is very hard to spot.
The second shows a typical commuter with lights, and also a high-visibility jacket and helmet – the latter are not mandatory, but are recommended by the Highway Code.
And in the final photo, the cyclist is wearing the latest and most complete reflective clothing.
PC Rob Hammond said: “The clocks go back at the end of October and this makes it darker in the evening.
“Many cyclists are unaware of the danger they present by not making themselves visible.
“Now is the time to make yourself as safe as you can be.”
The Echo’s photos show cyclists at 14 metres from a car’s headlights – the stopping distance at 30mph.
Police last year began a series of operations with a presence a Bournemouth Cemetery Junction in December.
Officers stopped 33 riders in two hours and issued fines. They plan to carry out another series of operations in the next few months.
Last winter, they concentrated on Wallisdown Road, a busy commuter spot that also includes the most accident prone spot for cyclists in the whole town, the roundabout which joins to Wimborne Road.
PC Hammond said: “Cyclists can change how they look to motorists relatively simply and cheaply – after all, how much is your life worth?”
Officers will be stopping riders in Bournemouth this autumn and issuing 30 fines, which are cancelled if offenders buy lights within seven days.
In the first photo, the rider has no night-time gear and is very hard to spot.
The second shows a typical commuter with lights, and also a high-visibility jacket and helmet – the latter are not mandatory, but are recommended by the Highway Code.
And in the final photo, the cyclist is wearing the latest and most complete reflective clothing.
PC Rob Hammond said: “The clocks go back at the end of October and this makes it darker in the evening.
“Many cyclists are unaware of the danger they present by not making themselves visible.
“Now is the time to make yourself as safe as you can be.”
The Echo’s photos show cyclists at 14 metres from a car’s headlights – the stopping distance at 30mph.
Police last year began a series of operations with a presence a Bournemouth Cemetery Junction in December.
Officers stopped 33 riders in two hours and issued fines. They plan to carry out another series of operations in the next few months.
Last winter, they concentrated on Wallisdown Road, a busy commuter spot that also includes the most accident prone spot for cyclists in the whole town, the roundabout which joins to Wimborne Road.
PC Hammond said: “Cyclists can change how they look to motorists relatively simply and cheaply – after all, how much is your life worth?”
Thursday, 15 September 2011
Lighting a spark
The buzz against corruption started by the Anna Hazare-led movement is being matched by welcome initiatives to clean the system, launched by several state governments. Using new legislative tools to crack down on erring bureaucrats and ensure smooth delivery of services to the people, they are setting new standards in public welfare. Most importantly, the aim is to provide good governance at the grassroots rather than focus on big-ticket legislations that may not directly affect the common man.
The lead in this regard has been taken by Bihar chief minister Nitish Kumar. And he started out much before Anna, the impetus in Bihar's case arising from the nadir of underdevelopment it had arrived at as a corruption-ridden BIMARU state prior to Nitish.
Chief among such initiatives is the Bihar Special Courts Act, 2009, which establishes special tribunals for the speedy trial of offences under the Prevention of Corruption Act. It is under the provisions of this new law that the swanky property of a Bihar-cadre IAS officer was recently seized and converted into a school for underprivileged children.
The example shows how liabilities can be turned into assets by a determined government. The state government also enacted the Right to Service Act this Independence Day, to provide time-bound public services across 10 departments such as issuance of driver's licence and other routine permits.
Similarly, the Delhi government has come up with its Right of Citizen to Time Bound Delivery of Services Act, 2011. Coming into force from today, the legislation seeks to ensure smooth service delivery in 28 categories such as issuance of a new electri-city connection, birth and death certificates and ration cards.
Apart from administrative action, delays will attract a monetary penalty, which will be deducted from the salary of the erring official. In Madhya Pradesh, the state administration is said to have disposed of 3.6 million complaints in less than a year under its Public Service Guarantee Act. In Chhattisgarh, PDS reforms such as handing over the running of PDS shops to gram panchayats and other community bodies have helped increase coverage of welfare schemes.
Such measures need to be encouraged to increase the scope for reforms and ensure transparency. The Aadhaar or Unique Identification project is a potent tool that should be leveraged to push initiatives such as rural banking and healthcare. E-governance must be pushed vigorously to ensure computerisation and transparency of government records. It is only through reducing the number of discretionary check posts in the government-public interface that corruption can truly be tackled.
The lead in this regard has been taken by Bihar chief minister Nitish Kumar. And he started out much before Anna, the impetus in Bihar's case arising from the nadir of underdevelopment it had arrived at as a corruption-ridden BIMARU state prior to Nitish.
Chief among such initiatives is the Bihar Special Courts Act, 2009, which establishes special tribunals for the speedy trial of offences under the Prevention of Corruption Act. It is under the provisions of this new law that the swanky property of a Bihar-cadre IAS officer was recently seized and converted into a school for underprivileged children.
The example shows how liabilities can be turned into assets by a determined government. The state government also enacted the Right to Service Act this Independence Day, to provide time-bound public services across 10 departments such as issuance of driver's licence and other routine permits.
Similarly, the Delhi government has come up with its Right of Citizen to Time Bound Delivery of Services Act, 2011. Coming into force from today, the legislation seeks to ensure smooth service delivery in 28 categories such as issuance of a new electri-city connection, birth and death certificates and ration cards.
Apart from administrative action, delays will attract a monetary penalty, which will be deducted from the salary of the erring official. In Madhya Pradesh, the state administration is said to have disposed of 3.6 million complaints in less than a year under its Public Service Guarantee Act. In Chhattisgarh, PDS reforms such as handing over the running of PDS shops to gram panchayats and other community bodies have helped increase coverage of welfare schemes.
Such measures need to be encouraged to increase the scope for reforms and ensure transparency. The Aadhaar or Unique Identification project is a potent tool that should be leveraged to push initiatives such as rural banking and healthcare. E-governance must be pushed vigorously to ensure computerisation and transparency of government records. It is only through reducing the number of discretionary check posts in the government-public interface that corruption can truly be tackled.
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