tefilla - What should a chazan do if he has theological problems with the congregation's text?

There are several places in the selichot where there are controversial phrases, e.g. addressing prayer to angels not G-d. I'm not asking for opinions on this, but I've heard some people just skip those lines. What do you do if you normally skip the lines, but are now chazan? How much license do you have to say "I just follow the congregation"?

Detect signals degree of imbalance

I have got this question: let's suppose that I have three signals, representative of the same variable, but taken on three different component of a same device; in my case, three load signals, representative of the out-of-plane bending moment Mx of each of the blade of a wind turbine.

Is it any possible to effectively and efficiently detect the degree of imbalance or asymmetry of such signals?

With asymmetry and imbalance I mean a single parameter/variable which gives information about how the three signals differ from each other.

I would then set-up a threshold value to this degree of difference, in order to further trigger a certain process when the threshold has been overcome.

The first idea I came up with is multiple correlation, but perhaps there exist tons of better methods.

EDIT

1. Each signal coming from each blade;


2. Blades placed with 120 deg phase shift;


3. Azimuth angle vs. Time available.


4. Regarding balance vs. unbalanced, I only know that unbalanced condition leads to higher loads on blades. In general, the three signals will always be unbalanced: what I would like to ascertain is the degree of imbalance; is it over a defined allowed limit or not?

Answer

One thing that can be useful in condition monitoring of rotating machines when rotation angle is important is to look at using circular or directional statistics.

Suppose your measurements are: $$ m_1(n), m_2(n), m_3(n) $$ for the three moments $m_i(n)$ for $i=1,2,3$.

Calculate the instantaneous directional mean of the moments: $$ m_{\rm tot}(n) = \left ( m_1(n) + m_2(n) e^{j2\pi/3} + m_3(n) e^{j4\pi/3} \right)\\ \bar{\phi}(n) = \arg \left( m_{\rm tot}(n) \right) $$ assuming that the first blade is your reference.

This direction, $\bar{\phi}$, is the direction of the average moment. If it's always aligned (or "anti-aligned") with one particular blade of your turbine, then that can indicate your "problem blade".

You can use the magnitude $$ \left| m_{\rm tot} \right| $$ as a measure of how "out of balance" the turbine is, as this should be (close to) zero most of the time.

If you have the azimuth angle, $\theta$, then you can get fancier. It may be that you need to angle-align (rather than time-align) your measurements to pick the faulty blade.

time - Why are Pidyon HaBen ceremonies done towards evening?

Most Brissim are done in the morning, as it is mentioned that "Zerizim Makdimim L'Mitzvos". Why is this not applicable to a Pidyon Haben ceremony? If it is applicable, then why have I observed that most people make Pidyon Habens towards evening?

Answer

It could be that such a custom exists because the baby needs to be 29.5611 days old and if he was born close to the end of one day, then in the summer when the nights are under 12 hours long, he would not be old enough first thing in the morning. (See R Akiva Eiger to Shach 305:12 and Pitchei Teshuva 305:17 who discuss similar concerns.)

て form - How to use the emotional って？

That comes from Ranma 1/2. Ranma asked Akane to wake up him up, and she did that by throwing water on him. He then said:

何しやがるんだ！

What the hell are ya doing!

When she left, he then thought out loud

くそー　アカネの奴。　まったく可愛くねー　起こし方しやがって！
That damn Akane, waking me up in the uncutest way ever!

I know "yagaru" is an unpositive version of "morau, kureru".

Yet, I'd instead say

おい、何しやがる｜しやがった！
ったくアカネの奴、全然可愛くねえ起こし方しやがった。

People said this "tte" makes the sentence more emotive. Can you guys explain this further, any give more examples of how to use it?

Answer

まったく可愛くねー　起こし方しやがって！

In colloquial speech, the te-form of a verb at the end of a sentence can express 非難 (reproach/criticism/condemnation) or 不満 (complaint/dissatisfaction).

Examples:

「太郎ったら、また脱いだものほったらかしにして！」
「もう、ケンカばっかりして！いいかげんにしなさい！」
「どいつもこいつも、俺をバカにしやがって！」

_{As a side note, the て-form at the end of a sentence can also express 命令/依頼(command/request), 釈明(explanation), 感嘆(exclamation), etc.}

inorganic chemistry - Predicting bond-strength of metal carbonyls

The metal carbonyls (and similar organometallic compounds) involve a combination of sigma bond, a pi bond and backbonding. The bond strengths under consideration are the metal-carbon bond and the carbon oxygen bond. Here is the original question:-

Predict the order of $\ce{C-O}$ bond strength in the following:-
I) $[\ce{Mn(CO)_6}]^+$
II) $[\ce{Cr(CO)_6}]$
III) $[\ce{V(CO)_6}]^-$

All of these are isoelectronic, and hence whatever the difference of bond strengths, must arise from the difference in the resultant nuclear force of attraction. Since $\ce{Mn+}$ has the highest charge density, I would assume that the $\ce{M-C}$ bond strength of the manganese compound is the strongest (vanadium being the weakest) and therefore, the $\ce{C-O}$ bond strength must follow the opposite order, as the strengthening of the metal carbonyl bond should weaken the carbon oxygen bond.

But the answer given is III, exactly the opposite of my prediction. Why is it so? A relevant factor which I didn't consider is the back bonding, but I am unsure of how to integrate that into my prediction. Also, how would we make a prediction if the given compounds were not isoelectronic?




transactions - Paying more for an item -- Ribis?

I will ask the question using the following scenario:

Reuvan wrote a sefer that he was charging for it 50 Shekels. Came along Shimon who wanted to buy the sefer. At that time he didn't have money on him so Reuvan agreed to give him the sefer now and that he could pay later. When Shimon came to pay a few days later he decided he wanted to give Reuvan a 100 shekels for the sefer instead of 50. His intention in giving it was to be for his (Reuvan's) benefit since he is a Talmud Chacham and wants to give him more for this sefer. Is there any problem of ribis with such a situation?

grammar - Are 終{お}わる and 済{す}ませる synonyms?

I know that they both mean "finish". But I wonder if there are situations or contexts where you can use one but not the other.

Answer

終わる/済む = intransitive. "to end/to come to an end/to be over/to finish etc."
終わらせる/終える/済ませる/済ます = transitive. "to finish/to end/to complete etc."

終わらせる sounds to me like "to make(force) something finish/to put an end to something", while 済ませる sounds like "to let something finish/to let something be over", and I think 済ませる is more used when you're talking about finishing something unfavourable.

We can say "~~との関係を終わらせる"(dump~~/break up with~~)/"~との関係は終わった"(broke up with~~) but not "~~との関係を済ませる"/"~~との関係は済んだ".

I think "(~~と/との)話を終わらせる" and "(~~と/との)話を済ませる" can mean the same thing (="to finish~~"). "話を終わらせる" can also mean "to stop talking to someone (before you finish)" but "話しを済ませる" can't.

I don't see any major difference between "宿題が済んだらゲームしよう" and "宿題が終わったらゲームしよう"/"仕事を済ませて帰宅する" and "仕事を終わらせて帰宅する/"仕事を終えて帰宅する".("終えて" sounds a bit literary.)

"済ます/済ませる" can also be used to say "~~なしで済ます/済ませる(=do without~~)", "~~で済ます/済ませる(=~~で間に合わせる/make do with~~)", but we can't rephrase them as "~~なしで終わらせる"/"~~で終わらせる".

"済む/済ませる" can also mean "解決する/to settle", e.g. "このままでは済まされないぞ"(We can't let the matter go at this)/"金で済む(or済まされる)問題じゃない"(You can't settle the matter with money)/"軽いけがで済んだ"(I escaped with only a minor injury)/"気が済むまで殴れ！"(Hit me until you're satisfied), and you can't use 終わる/終わらせる for these expressions.

You can say "任務を終えて帰国する"(carry out one's duty)/"70歳で生涯を終える"(die at the age of 70) but not "任務を済ませて/生涯を済ませる".

(Hmm I don't think this is all...there must be a lot more than this.)