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Can concrete lose strength during curing?

We cast a bridge's concrete deck and kept samples for concrete strength tests at 7 and 28 days. We took a test at 7 days, and the test result were over the design strength (designed for 30 MPa, result was 33 MPa). The control engineer insisted that…
Murat Dal
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What is 'No Detent Torque'?

I am learning about Variable Reluctance ( VR ) Stepper Motors. As stated in my reference, they "have no detent torque." What does this mean?
Ciambro
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Are there solutions for coupling a spline shaft to a round diameter shaft

I only have basic metal fabrication tools and do not own a mill or a lathe, but would like one. I took apart my cheap drill press to study whether or not I can convert it into a milling machine. The spindle features a 4 tooth 9mm x 9mm tooth male…
user148298
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What is the splice length for two reinforcement bars in tension of different diameter?

For reinforcing in concrete, anchorage / lap lengths are determined by the multiplying the diameter of the rebar with a factor. Generally a factor of 40-45 is accepted as the de-facto standard. According to EC2, the factor falls within the range…
SlydeRule
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Fuzzy control of anti-lock brake system

I was just reading about the anti-lock brake system example on the wiki page for fuzzy control system. The principle seems to be simple: instead of just assigning a SINGLE category (cold, cool, nominal, warm or hot) to the temperature of the brake,…
hooyeh
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Do bolts become tighter or looser at cryogenic temperature?

In general, will screws tightened at room temperature become tighter or looser at very low temperature (5 K)? On the one hand, the screw should loosen because it will contract radially, while the surrounding material will contract slightly less (or…
ninemileskid
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Controlling the temperature with high precision

I need to control the temperature with high precision, and for this task would be good a temperature controller with pt-100 sensor, something like this one PID Temperature Controller ITC-100. As I see that, it can be very simple: there is an input…
Antonio
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What if project requirements depend on discoveries while designing?

I asked a question where a comment pointed out: Requirements are things that you should be drafting to figure out what you want, before you know exactly how you are going to solve it. I was doing it backwards. I was going to define requirements…
Jayy
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Computer engineering vs Computer Science?

Sorry if this is in the wrong place; I haven´t posted in SE Engineering before, and the site said that SEE is also for students. I´m a High School senior and I´m debating between Computer Engineering and Computer Science. Can someone give me…
JKlemm
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Why wont Petrol engine run on Acetylene?

Boiling temperature of Acetylene is -84°C and that of Petrol is 95°C (at Atmospheric Pressure). So the spark is efficient to ignite the compressed Acetylene and run the Engine. But why wont that work ? Is any other factor that I miss or…
Dasaradh M S
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Why does a continuous beam have less deflection than a pair of simply supported beams?

Inspired by this question, and also this answer to a separate question. I have two beam models, one with two independent spans (a full hinge), another is a continuous beam over both spans (only column is hinged), the below is the diagram of both…
Graviton
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Why 0.2% of strain is considered while taking proof stress?

When a material does not show a distinct yield point then 0.2% of strain is considered and a line is drawn parallel to the elastic line and the corresponding stress is called proof stress. My question is why are they taking 0.2% of strain? Is that…
user6538
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Circuit Design Inductor Problem

I am having trouble finding a 3.4 µH through hole inductor that is in stock right now. I was wondering if I can just place 2 inductors that add up to 3.4 µH in series to solve this problem. I am not sure if this would introduce any problems, if so…
user3897744
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LTE channel characterization from Time Domain waveform

I am currently interested into the diverse Downlink LTE channels broadcasted over air after some (QPSK, 16QAM...) modulation. More precisely their waveform. I would like to know if, with a good filtering of the noise, we could characterize the LTE…
Amesys
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Structural Analysis of a Space Frame

I have a seemingly simple structure and I need to perform a hand calculation to check that the stresses in the members are below the allowable values. In its simplest form, the structure is a rectangular frame made from rectangular tube welded at…
Jim S.
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