This is incorrect. If R1 is infinite and R2 is 0, the parallel impedance is 0 ohms, but the input impedance is much higher than the input impedance of the op-amp itself, due to feedback making the inputs very similar in voltage.

The input impedance is actually

$$(1 + A_0 B)\cdot Z_\mathrm{ino}$$

where

• \(A_0\) is the gain without feedback (the open loop gain)
• \(B\) is the fraction of the output which feeds back as a negative voltage at the input
• \(Z_\mathrm{ino}\) is input impedance without negative feedback

For the above buffer example, it would be close to \(A_0 Z_\mathrm{ino}\)

See https://electronics.stackexchange.com/q/177007/142

Simpson - Introductory electronics for scientists and engineers section 7.2 Negative Voltage Feedback explains this clearly

Want to explore what this might look like in an engineering course. Need to identify examples.

Possible source example for use in an open engineering text.

https://github.com/OpenEngr/engineering-the-book

Equation 10-27 is wrong:

• Resistors are in parallel, their noise does not sum.

This is 3 terms (10 MΩ noise, 100 kΩ noise, and amplifier noise), but the equation only includes 2.

Equation 10-25 has several errors:

• The left and right side are not equal.
• Resistors are in parallel, so their noise does not sum.
• Resistor noise needs to be multiplied by gain to be combined with 113.1 μV output noise of op-amp.

Equation 10-23 is incorrect:

• The noise of the resistors does not sum, since the resistors are in parallel and load each other. It would be equal to a single 50 kΩ resistor producing 4.0 μV.
• The 113.1 value is output noise. The resistor noise needs to be multiplied by the gain to get the output noise, too.

Should be 0.1 μF

Should be 0.1 μF

The noise calculations have many errors. See annotations on https://via.hypothes.is/http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf for details

actually should be multiplied by the non-inverting noise gain, which is 101

Should be TLC2201

The noise calculations have many errors. See annotations on https://via.hypothes.is/http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf for details

Language can be found related to this in many engineering codes of ethics.

Figure 8 on page 22 shows OA percentages for a number of engineering disciplines. Most of which appear near the bottom of the chart.

This is incorrect:

• The poles are not located on a circle
• The imaginary parts of the poles are not equally spaced

To generate the poles of a Bessel filter you need to use root-finding methods on the reverse Bessel polynomials. There's no other shortcut that I'm aware of.

This is incorrect: There is a small amount of overshoot in Bessel filters.

This isn't quite correct: Bessel filters have a small amount of overshoot.

The Long Now Foundation and its views open up a whole chasm of moral, ethical, and legal questions with this 'DeExtinction Movement'. How is genetically engineering endangered species a form of 'genetic rescue'? These species are dying out because of man and man's actions, which is a terrible reflection of the worst part of human nature, but it does not give us the right to clone nature and 'whitewash' all that we have done before. Just because we may have the capacity to do so, does not mean we should. We cannot simply decide that extinction is fine because we can create genetically engineered species in the future to 'make up' for our mistakes. How are we expected to learn from our mistakes if we can simply rewind and start again?

Dr. Kenneth Adam, who worked on the Environment Protection board during the Mackenzie Valley Pipeline Inquiry, spent the majority of his career working as a professional engineer with numerous engineering companies and private consulting firms. Some of his experiences included working for Templeton Engineering (for additional information, see the annotation for Carson Templeton), I.D. Engineering, Sentar Consultants, and Earth Tech Canada. In addition to working in industry, Dr. Ken Adam had a highly successful career in academia. He was an associate professor at the University of Manitoba working in the Department of Civil Engineering from 1972 to 1976. Dr. Ken Adam specialized in the construction of winter roads, specifically in the Canadian North. Due to his expertise, he was able to publish several articles on the construction of winter roads. The topics of his papers included the environmental impact of snow and ice roads, the development of improved snow blowers and pavers, and much more. His journal article entitled “Snow and Ice Roads: Ability to Support Traffic and Effects on Vegetation” was published in March of 1977 in the Arctic journal Volume 30 Number 1 (Adam and Hernandez 1977). He had another journal article published in the Journal (Water Pollution Control Federation) Volume 46 Number 12 entitled “Hydraulic Analysis of Winnipeg Sump Inlets” in December of 1974 (Adam and Brandson 1974). These are just two of many articles Dr. Ken Adam has published. These papers were researched and published for the government and private business. His clients included the Department of External Affairs, Indian and Northern Affairs Canada, the Izok project, the Environment Protection Board, and others. Currently, Dr. Ken Adam resides in Winnipeg, Manitoba (Elves 2009). 

References

Adam, Kenneth M., and Normal B. Brandson. "Hydraulic Analysis of Winnipeg Sump Inlets." Water Environment Federation, 1974: 2755-2763.

Adam, Kenneth, and Helios Hernandez. "Snow and Ice Roads: Ability to Support Traffic and Effects on Vegetation." Arctic, 1977: 13-27.

Elves, Daniel. Libraries of the University of Manitoba. January 2009. https://umanitoba.ca/libraries/units/archives/collections/complete_holdings/ead/html/Adam.shtml#tag_bioghist (accessed April 9, 2017).

Carson H. Templeton was born in Wainwright, Alberta. He earned a diploma studying Mining Engineering at the Southern Alberta Institute of Technology (SAIT) in Calgary, Alberta. He worked at the Madsen Red Lake Mine in Northwest Ontario as an Assistant Assayer, Boat Boy, and Post Office Manager. He attended the University of Alberta to continue his studies of Mining Engineering and graduated with a Bachelor of Science. During World War II, Templeton worked on the Canol Pipeline Project. He then helped construct airports alongside the Alaska Highway for military use. In 1948, Templeton was appointed Assistant Chief Engineer of the Fraser Valley Dyking Board. In 1950, Templeton was appointed Chief Engineer of the Greater Winnipeg Dyking Board. In 1955, Templeton founded a consulting engineering firm which he named the Templeton Engineering Company. Before the Unicity Amalgamation of Winnipeg in 1972, his company worked as the City Engineer for several small cities in Canada. His company performed engineering estimates for the Royal Commission on Flood Cost-Benefits. These calculations led to the construction of the Winnipeg Floodway. Additionally, Carson Templeton’s consulting engineering firm conducted research that supported the writing of “Snow and Ice Roads: Ability to Support Traffic and Effects on Vegetation” by Kenneth Adam and Helios Hernandez (Adam and Hernandez 1977). In 1966, his company merged with Montreal Engineering and Shawinigan Engineering to form Teshmont Consultants Ltd. Teshmont Consultants Ltd. has completed over 50 percent of the world’s high-voltage, direct current projects. Templeton served as the Chairman of the Alaska Highway Pipeline Panel and Chairman of the Environmental Protection Board during the 1970s. As the Chairman of the Environmental Protection Board, Templeton orchestrated the hearing process for the Environmental Impact Assessments for the Mackenzie Valley Pipeline Inquiry (Winnipeg Free Press 2004). 

References

Adam, Kenneth, and Helios Hernandez. "Snow and Ice Roads: Ability to Support Traffic and Effects on Vegetation." Arctic, 1977: 13-27.

Winnipeg Free Press. Carson Templeton OC. October 10, 2004. http://passages.winnipegfreepress.com/passage-details/id-89334/Carson_Templeton_#/ (accessed April 8, 2017).

This is a great, short guide for optimizing pull requests for review-ability.

Lots to be said about misdirected problem-solving. Much of it has to do with people who are extremely competent at their job but whose job is narrower than it could be. For instance, engineers are unbelievably adept at finding a solution to almost any problem. But it’s relatively common for them to work on “the wrong problem”, something which may not even need solving in some cases or a solution which may bring completely new problems. Those who think of the human condition as a problem to be solved may apply this type of mindset to an inappropriate extreme. Hence Soylent and VR goggles for prisoners.

Sounds a bit restrictive. Though there are hairy UX problems making it even more difficult for teachers to contribute content, many other issues are likely to remain, preventing contributions, even if the User Experience were optimal for every single potential contributor. In other words, it’s one thing to set “the problem to be solved” in a manageable way. It’s another to grasp the complexity of the situation.

算法开发工作就有这种特点

Sounds somewhat like agile devlopment.

In summary, teams which are "fairer", in two senses, tend to be more effective:

• Those where members speak and contribute in roughly the same proportion (albeit possibly in quite different ways)
• Those where members have an above-average sensitivity to what others are thinking and feeling

Design-Oriented Analysis Rules and Tools, Dr. R. David Middlebrook

Real problems usually have more variables than equations. So approximations and inequalities are essential.

Computer hardware is also full of bugs.

The collapse of the Tacoma Narrows bridge in 1940 was caused by flutter, not resonance. And sometimes the film is played too fast.