The key advantages of lasers over other light sources are:
- lasers emit a narrow spectrum
- it can be efficient collimated, while still emitting a lot of output power: Section "Why can't you collimate incoherent light as well as a laser?"
- can be phase and polarization coherent, though it is not always the case? TODO.
One cool thing about lasers is that they rely on one specific atomic energy level transition to produce light. This is why they are able to to be so monchromatic. Compare this to:As such, lasers manage to largely overcome "temperature distribution-like" effects that create wider wave spectrum
- incandescent bulbs: wide black-body radiation spectrum
- LED: has a wider spectrum fundamentally related to an energy distribution, related: Why aren't LEDs monochromatic
- TODO think a bit about fluorescent lamps. These also rely on atomic energy transitions, but many of them are present at once, which makes the spectrum very noisy. But would individual lines be very narrow?
Crazy difference between 5W laser and 5W LED by Brainiac75
. Source. Baseic but good. Uses a laser photometer.en.wikipedia.org/w/index.php?title=Andr%C3%A9-Marie_Amp%C3%A8re&oldid=1211946256:TODO find the source for this.
Jean-Jacques Ampère, a successful merchant, was an admirer of the philosophy of Jean-Jacques Rousseau, whose theories of education (as outlined in his treatise Émile) were the basis of Ampère's education. Rousseau believed that young boys should avoid formal schooling and pursue instead a "direct education from nature." Ampère's father actualized this ideal by allowing his son to educate himself within the walls of his well-stocked library.
One more more electrical wires surrounded by an insulator.
He participated in the development of the electrical telegraph, and he did some good modeling work that improved the foundations of the field, notably creating the telegrapher's equations.
He was one of those idealists who just want to do some cool work even if they have to starve for it, people had to get a state pension for him for his contributions. Nice guy. en.wikipedia.org/w/index.php?title=Oliver_Heaviside&oldid=1230097796#Later_years_and_views:He also never married: www.nndb.com/people/627/000204015/
In 1896, FitzGerald and John Perry obtained a civil list pension of £120 per year for Heaviside, who was now living in Devon, and persuaded him to accept it, after he had rejected other charitable offers from the Royal Society.
CIA 2010 covert communication websites 2013 DNS census secureserver.net MX records intersection 2013 DNS Census virtual host cleanup by 
Ciro Santilli 37 Updated 2025-05-23 +Created 2023-07-19
Ciro Santilli 37 Updated 2025-05-23 +Created 2023-07-19We intersect 2013 DNS Census virtual host cleanup with 2013 DNS census MX records and that leaves 460k hits. We did lose a third on the the MX records as of 260 hits since secureserver.net is only used in 1/3 of sites, but we also concentrate 9x, so it may be worth it.
We did a full Wayback Machine CDX scanning for JAR, SWF and cgi-bin in those, but only found a single new hit:
- 63.130.160.50 theglobalheadlines.com. Just barely missed with our 2013 DNS Census virtual host cleanup heuristic keyword searches as we did think of both "global" and "headlines" in the "news" themes!
Update multiple rows with different values in a single SQL query by Ciro Santilli 37 Updated 2025-05-23 +Created 1970-01-01
Ciro Santilli 37 Updated 2025-05-23 +Created 1970-01-01Vertebrates minus tetrapods.
This paraphyletic subgroup is easy to form the "acquatic only" (fishes) vs "things that come out of water" (tetrapods). Though mudfishes make that distinction harder.
Which kind of makes sense, why would you want for limbs unless you are going to stay out of water!
sqlite3 ':memory:' 'WITH t (i) AS (VALUES (-1), (-1), (-2)) SELECT *, row_number() over () FROM t'-1|1
-1|2
-2|3With a possible output:
partition by:sqlite3 ':memory:' 'WITH t (i) AS (VALUES (-1), (-1), (-2)) SELECT *, row_number() over ( partition by i ) FROM t'-2|1
-1|1
-1|2rm -f tmp.sqlite
sqlite3 tmp.sqlite "create table t (id integer, val integer)"
sqlite3 tmp.sqlite <<EOF
insert into t values
(0, 0),
(1, 5),
(2, 10),
(3, 14),
(4, 15),
(5, 16),
(6, 20),
(7, 25),
(8, 29),
(9, 30),
(10, 30),
(11, 31),
(12, 35),
(13, 40)
EOFShow how many neighbours each column has with Output:
val between val - 2 and val + 2 inclusive:sqlite3 tmp.sqlite <<EOF
SELECT id, val, COUNT(*) OVER (
ORDER BY val RANGE BETWEEN 2 PRECEDING AND 2 FOLLOWING
) FROM t;
EOF0|0|1
1|5|1
2|10|1
3|14|3
4|15|3
5|16|3
6|20|1
7|25|1
8|29|4
9|30|4
10|30|4
11|31|4
12|35|1
13|40|1val - 1 and val + 1 inclusive instead:sqlite3 tmp.sqlite <<EOF
SELECT id, val, COUNT(*) OVER (
ORDER BY val RANGE BETWEEN 1 PRECEDING AND 1 FOLLOWING
) FROM t;
EOF0|0|1
1|5|1
2|10|1
3|14|2
4|15|3
5|16|2
6|20|1
7|25|1
8|29|3
9|30|4
10|30|4
11|31|3
12|35|1
13|40|1There seems to be no analogue to HAVING for window functions, so we can just settle for a subquery for once, e.g.:which outputs:
sqlite3 tmp.sqlite <<EOF
SELECT * FROM (
SELECT id, val, COUNT(*) OVER (
ORDER BY val RANGE BETWEEN 1 PRECEDING AND 1 FOLLOWING
) as c FROM t
) WHERE c > 2
EOF4|15|3
8|29|3
9|30|4
10|30|4
11|31|3stackoverflow.com/questions/17046204/how-to-find-the-boundaries-of-groups-of-contiguous-sequential-numbers/17046749#17046749 just works, even in SQLite which supports all quoting types known to man including
[] for compatibility with insane RDBMSs!Here's a slightly saner version:
rm -f tmp.sqlite
sqlite3 tmp.sqlite "create table mytable (id integer primary key autoincrement, number integer, status integer)"
sqlite3 tmp.sqlite <<EOF
insert into mytable(number, status) values
(100,0),
(101,0),
(102,0),
(103,0),
(104,1),
(105,1),
(106,0),
(107,0),
(1014,0),
(1015,0),
(1016,1),
(1017,0)
EOF
sqlite3 tmp.sqlite <<EOF
SELECT
MIN(id) AS "id",
MIN(number) AS "from",
MAX(number) AS "to"
FROM (
SELECT ROW_NUMBER() OVER (ORDER BY number) - number AS grp, id, number
FROM mytable
WHERE status = 0
)
GROUP BY grp
ORDER BY MIN(number)
EOFoutput:
1|100|103
7|106|107
9|1014|1015
12|1017|1017To get only groups of length greater than 1:
sqlite3 tmp.sqlite <<EOF
SELECT "id", "from", "to", "to" - "from" + 1 as "len" FROM (
SELECT
MIN("id") AS "id",
MIN(number) AS "from",
MAX(number) AS "to"
FROM (
SELECT ROW_NUMBER() OVER (ORDER BY "number") - "number" AS "grp", "id", "number"
FROM "mytable"
WHERE "status" = 0
)
GROUP BY "grp"
ORDER BY MIN("number")
) WHERE "len" > 1
EOFOutput:
1|100|103|4
7|106|107|2
9|1014|1015|2 There are unlisted articles, also show them or only show them.