Wikipedia:Reference desk/Archives/Science/2018 August 9

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August 9

Please explain this power plant availability formula specially the summation part

thermal generating station for any period means the average of the daily average declared capacities for all the days during that period expressed as a percentage of the installed capacity (in MW) of the generating station minus normative auxiliary consumption as specified in these regulations and shall be computed in accordance with the following formula; N Availability = 10000 × Σ DCi

/ {N × IC × (100 – AUXn

)} % i = 1 Where — N = Number of time blocks in the given period as may decided by the Commission from time to time; DCi

= Average Declared ex-bus Capacity in MW for the ith time block in such period;

IC = Installed Capacity of the generating station in MW; AUXn

= Normative auxiliary consumption as a percentage of gross generation;45.120.17.7 (talk) 04:22, 9 August 2018 (UTC)

Here is how I think your text should appear. The underlined parts are my guesses that could be wrong.

The availability of a thermal generating station for any period means the average of the daily average declared capacities for all the days during that period expressed as a percentage of the installed capacity (in MW) of the generating station minus normative auxiliary consumption as specified in these regulations and shall be computed in accordance with the following formula.

$Availability=$100$*\sum _{i=1}^{N}DC_{i}/(N*IC*(100-AUX_{n}))\%$

where:

$N=$ Number of time blocks in the given period as may decided by the Commission from time to time

$DC_{i}=$ Average Declared ex-bus Capacity in MW for the $i$th time block in such period

$IC=$ Installed Capacity of the generating station in MW

$AUX_{n}=$ Normative auxiliary consumption as a percentage of gross generation

(more follows)

Explanation: If $N=3$ the summation part $\sum _{i=1}^{N}DC_{i}$ would be calculated as $DC_{1}+DC_{2}+DC_{3}$. DroneB (talk) 15:43, 9 August 2018 (UTC)

It's not clear from the original whether the denominator (N*IC*AUXn) is part of the summation terms or whether it should be a denominator for the summation as a whole. What is the order of operations precedence of sigma-summation vs division? Mathematically it doesn't matter, but either way, it would be clearer (and one less level of parens) to write the fraction as a fraction:

$Availability=\sum _{i=1}^{N}{\frac {DC_{i}}{N*IC*(100-AUX_{n})}}*100\%$

or

$Availability={\frac {\sum _{i=1}^{N}DC_{i}}{N*IC*(100-AUX_{n})}}*100\%$

DMacks (talk) 17:34, 9 August 2018 (UTC)

I think the "100" is wrong (or at least the overall context is confusing) because the "100-AUXn" term in the denominator means we are in something like "1/%" units. To get to normal fractional values, we need to multiply that by 100. To get that to percent (consistent with how AUXn is), we need to multiply by 100 again. So it should be 10000 not 100.

IP, it would be useful when you ask these questions to give a link or context to where to are reading something you would like explained. I found the formula (confirming "*10000" not "*100") by googling ["power plant" availability "auxn"]. DMacks (talk) 18:09, 9 August 2018 (UTC)

Drowning

According to Drowning#Forensics, "Forensic diagnosis of drowning is considered one of the most difficult in forensic medicine", etc. This is surprising. Aren't considerable amounts of aspirated seawater or fresh water in the victims' lungs a reliable sign of drowning? Additionaly, at least seawater should leave salt traces on the victims' skin and elsewhere, corroborating the diagnosis. I remember that the first aid involves expelling the aspirated water from the victim's respiratory system. Thanks. 212.180.235.46 (talk) 16:21, 9 August 2018 (UTC)

After you have read the cited section do you know some easy way to distinguish whether the death was due to immersion, or whether the body was immersed post mortem? DroneB (talk) 17:08, 9 August 2018 (UTC)

See also Diagnostic of Drowning in Forensic Medicine; "The diagnostic of drowning is described in the literature as one of the most difficult in the field of forensic medicine... The main goal in this field is to differentiate a death by submersion from an immersion of a body. Death of a victim found in water should not always be related to drowning". Alansplodge (talk) 18:58, 9 August 2018 (UTC)

It's odd though, because as far back as old Agatha Christie's and the like—and possibly earlier—a well-known trope is that water only gets into the lungs whilst they are working; i.e., while the victim is alive. In other words, the presence of water in the lung indicates drowning and the lack of it, immersion post-mortem. H'mmm. —SerialNumber54129 ^{paranoia /cheap sh*t room} 14:20, 10 August 2018 (UTC)

The source linked above and Drowning: Still a difficult autopsy diagnosis both consider testing to determine if diatoms found in the water in the lungs have passed into the circulatory system, which would indicate drowning. This seems to contradict Christie's hypothesis. Alansplodge (talk) 12:08, 12 August 2018 (UTC)