Stick stiffness

Square drill collars are used to increase the stiffness of the drill string and are recommended for drilling in crooked hole areas. The spiral type of drill collar is used for drilling formations in which the differential pressure can cause sticking of drill collars. The spiral grooves on the drill collar side reduce the area of contact between drill collar and wall, which considerably reduces the sticking force. 

Stick-slip motion is another issue that has been explored using SFA. It is found that the occurrence of stick-slip depends on the sliding velocity and the stiffness of the system, and the mechanism of the phenomenon can be interpreted in terms of periodic transition between liquid and solid states of the conhned lubricant [40],... 

Some infinitives seem to improve on being split, just as a stick of round stovewood does. I cannot bring myself to really like the fellow. The sentence is relaxed, the meaning is clear, the violation is harmless and scarcely perceptible. Put the other way, the sentence becomes stiff, needlessly formal. A matter of ear. 

The towed sled is the most common form of test and many such apparatus have been devised. Whilst simple in principle, there are practical problems in that the sled will tend to tilt if it is not towed on the plane where the surfaces meet, and if the means of applying the force is a wire or cord, the lack of stiffness can cause slip-stick. 

Assuming the C-C bonds of the prism all are the same length, determine how many mono-, dr-, and tribromine-substituted isomers are possible for 17. Compare the results with those expected for benzene with structure 13. If you have molecular models of the ball-and-stick type, these will be very helpful. A simple alternative model for 17 would be a piece of stiff paper folded and fastened as in 18 to give a prism with three equal square faces. 

To avoid stick-slip, one should try to make the spring constant high enough (using stiff materials and stable constructions). It can be shown, that stick-slip may also arise from the velocity dependence of the friction coefficient [460], When the friction coefficient decreases with sliding velocity, stick-slip is amplified. When the friction coefficient increases with velocity, stick-slip is damped out. The former is usually the case at low speeds, certainly for the transition from static to dynamic friction, whereas the latter prevails usually at high velocity. 

For non-spherical particles the relations are different this is easiest demonstrated by the Einstein formula the coefficient ky increases when the particles are flattened, and even stronger upon elongation. An example of the latter case When a sphere is extended up to a length/diameter ratio of 10, ky increases from 2.5 to 6. Sticks and platelets, therefore, have a stronger effect this accounts for the fact that with a volume fraction of 20 % increases in stiffness up to a factor of 3 are measured, whereas the Kemer formula would predict a much lower value. 

Initially, of course, we heard about the Inuit Eskimos of Greenland and how they almost never developed heart disease even though they ate large amounts of fat in the form of fish and marine animals. At first glance, that appeared paradoxical. Then came the realization that the fat consumed was a kind of polyunsaturated fatty acid termed omega-3.Think about it if the fat in coldwater fish were saturated, those fish would be as stiff and hard as a stick of butter in the refrigerator. 

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