Mehmet Can ÇAPAR 030070131 10th week definitions Part 2

3-Measurement Circularity (measurment property)

(there is no old answer)

(new answer)

In his famous discussion of the difficulties of the empirical testing of scientific theories, Pierre Duhem made the curious statement that "the experimental testing of a theory does not have the same logical simplicity in physics as in physiology" ([19061 1962, sec. 2.6.1, 180-183). The physiologists can make their observations by means of laboratory instruments that are based on the theories of physics, which they take for granted. However, in testing the theories of physics, "it is impossible to leave outside the laboratory door the theory we wish to test." The physicists are forced to test the theories of physics on the basis of the theories of physics. Among physicists, those who are involved in the testing of complicated and advanced theories by means of elementary observations would be in a relatively straightforward epistemic position, much like Duhem's physiologists. But for those who try to justify the reasoning that justifies the elementary observations themselves, it is very difficult to escape circularity. The basic problem is clear: empirical science requires observations based on theories, but empiricist philosophy demands that those theories should be justified by observations, And it Is. in the context of quantitan"ve measurement, where the Justification needs to be made most precisely, that the problem of circularity emerges with utmost and unequivocal clarity.

In each of the preceding chapters I examined how this circularity of justification manifested itself in a particular episode in the development of thermometry and how it was dealt with, Chapter 1 asked how certain phenomena could have been Judged to be constant in temperature, when no standards of constancy had been established previously. The answer was found within the self-improving spi_ral of quantification-starting with sensations, going through ordinal thermoscopes, and finally arriving at numerical thermometers. Chapter 2 asked how thermometers relying on certain empirical regularities could be tested for correctness, when those regularities themselves would have needed to be tested with the help of thermometer readings. The answer was that theml ometers could be tested by the criten.on of comparability, even if we could not verify their theoretical justification. Chapter 3 asked how extensions of the established thermometric scale could be evaluated, when there were no pre-existing standards to be used in the new domains, The answer was that the temperature concept in a new domain was partly built through the establishment of a convergence among various proposed measurement methods applying there, Chapter 4 asked how methods of measuring abstract concepts of temperature could be tested, when establishing the correspondence between the abstract concept and the physical operations relied on some theory that would itself have required empirical verification using results of temperature measurement, The answer was found in the iterative investigation based on the provisional assumption of an unjustified hypothesis, leading to a correction of that initial hypothesis.

(Hasok Chang, Inventing Temperature: Measurement and Scientific Progress, pg: 221)

4- Single spindle automatic lathes (mechanism)
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(new answer)

            This machine often called a screw machine because of its widespread use for rapid manufacture of turned and die-threaded small screws from bar-stack, is representative of the majority of the ideas incorporated in mechanically controlled automatic machines.

            Figure 7.4 gives a schematic arrangement of an SS Auto. Mechanical control of this machine depends upon the drive to the back shaft on which clutch mechanisms of the type shown Figure 7.1 and other devices are mounted. The back shaft is linked by change gears and a worm reduction gear to the front shaft and the turret cam shaft. These shafts are arranged to make one completed revolution while the headstock spindle makes the number of revolutions needed for machining the parts. The front shaft rotates the front and rear slide cams and, via trip mechanisms, operates collet opening, spindle speed changes, turrets indexing etc. Data are given in the machine handbook for preparing an operation layout with timing based on headstock spindle revolutions, and fort he design of the special cams where the unit used is 1/100 of the cam circle. Such a machine is automatic in operation except fort he manual loading of bar stock as it is consumed.

V. Chiles,Stewart C. Black,A. Lissaman, Principles of Engineering Manufacture, pg: 186,187)