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Vol. 16, No. 4 (1960)

1960-02-20
CONTENT
1960, 61 (4): 187-188. doi: 10.7498/aps.16.187
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THEORY OF HIGH ORDER ABERRATIONS
WANG CHIH-CHIANG
1960, 61 (4): 189-204. doi: 10.7498/aps.16.189
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This paper is to discuss the properties of high order aberrations taking advantage of as much as possible of using the methods of approximation. The number of independent terms of secondary aberrations is first accessed and its geometrical significance ascertained. By a coordinate transformation the effects of the change of stop position on aberration coefficients are determined. The relations between the position of the object and its aberration coefficients are found on the basis of Fermat principle, by regarding each ray as emitting from different object points lying along this ray.The high order aberrations can be regarded as coming from two sources. The first is of "intrinsic" origin caused by the refracting surface proper, the incident beam being regarded free from abberations. All aberrations of this origin can be represented in terms of high order spherical aberration and off-axis spherical aberration introduced by the respective surface. The other is of sequential character, introduced on account of the presence of primary aberration of the incident beam introduced by the preceeding refracting surfaces.The derivations so arrived may not accord exactly with theory but they are close enough for practical purposes so as to access the origin of various aberrations as well as to give a quantitative estimation of them.The application of Fermat principle to the question of high order chromatic aberration with advantage takes into account of the fact that the method is true only because all other aberrations are already nearly corrected in a given optical system.
THE ABERRATIONS OF CYLINDRICAL OPTICAL SYSTEMS
WANG CHIH-CHIANG
1960, 61 (4): 205-213. doi: 10.7498/aps.16.205
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This paper deals with the aberrations of optical systems consisting of cylindrical components with their axes, parallal and having a common axis of symmetry. By symmetry and by a proper choice of the parameters for describing an optical ray, it is found that for primary aberrations the independent aberration terms amount to eight. For a. telescopic system the number of terms reduces to six. By method of vector analysis, it is further proved that the skew rays passing through such a systems is equivalent to a ray-tracing passing through its principal section but with the respective refractive index of each medium changed from n to (n2-η2)1/2, η being the direction cosine of the ray in the direction of cylindrical axes times n, an invariant throughout the system for a given ray. Thus the two term specifying "cylindrical" aberrations proper in a telescopic system (the other four terms being exactly the same as for spherical surfaces) can be treated in a similar way as longitudinal and transversal "chromatic" aberrations. However, the connection of such aberrations requires choice of optical materials difficult to comply with what is necessary for proper chromatic correction. On the otherhand, the serious effect of distortion usually found in cylindrical telescopic systems should be attributed as mainly intrinsic to Gaussian optics with which the practical requirement in imagery in such systems does not fully agree.
A MAGNETIC STUDY OF SOME IRON-NICKEL-ALUMINUM ALLOYS
WANG HUAN-YUAN, CHANG SHOU-KUNG, PAN SHIAO-THUR
1960, 61 (4): 214-228. doi: 10.7498/aps.16.214
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A detailed thermomagnetic analysis was carried out on a number of alloys along a tie-line in the two-phase (β+β′) region of the Fe-Ni-Al ternary system. The supersaturated solid solution, obtained by quenching an alloy close to the composition Fe2NiAl, broke up very fast at relatively high temperatures (~850℃), precipitation being completed in a little more than a minute. The β′ phase formed at 850℃ still contained about 35 at. % iron, with a Curie point near 400℃. When this alloy, after going through such a short tempering at 850℃ followed by quenching, was heated up to 600-700℃ again, the β′ phase formed during the first tempering continued to decompose rapidly, losing enough iron to become nonmagnetic in not much more than ten minutes. This caused the room-temperature coercive force of the alloy to rise to about 500 Oe. Such a phenomenon is in agreement with Б.Г.Лившнц's. suggestion of "post-precipitation". The magnetic measurements showed, moreover, that the post-precipitatioa of the β′ phase was "reversible", that is, when the alloy was brought up to 850℃ again after quenching from the second tempering at 600-700℃, the β′ phase could recover its equilibrium composition for 850℃ in a few minutes. Decomposition of the supersaturated solid solution Fe2NiAl at relatively low temperatures (below 700℃) was quite slow, and, furthermore, there was considerable evidence that the process was "non-uniform". On the basis of the above findings, the fact that high coercive force in the alloy Fe2NiAl cannot be obtained by quenching from above the solution temperature plus tempering at relatively low temperatures (600-700℃) is interpreted in the light of the single-domain particle theory.
BRIEF REPORT
1960, 61 (4): 241-244. doi: 10.7498/aps.16.241
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1960, 61 (4): 245-246. doi: 10.7498/aps.16.245
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