Everyone who develops software knows that it is a complex and risky business, and its participants are always on the lookout for new ideas that will lead to better software. Fortunately, software engineering is still a young and growing profession that sees innovations and improvements in best practices every year. Just look, for example, at the improvements and benefits that lean and agile thinking have brought to software-development teams. Successful software-development teams need to strike a balance between quickly delivering working software systems, satisfying their stakeholders, addressing their risks, and improving their ways of working. For that, they need an effective thinking framework that bridges the gap between their current ways of working and any new ideas they want to adopt. This article presents such a thinking framework in the form of an actionable kernel, which could benefit any team wishing to balance their risks and improve their way of working. INSPIRATION Work on the kernel, the essence of software engineering, was inspired by and is a direct response to the SEMAT (Software Engineering Methods and Theory) call for action (see figure 1). It is, in its own way, one small step toward redefining software engineering. SEMAT was founded in September 2009 by Ivar Jacobson, Bertrand Meyer, and Richard Soley, who felt the time had come to fundamentally change the way people work with software-development methods. 3,4,8 They wrote a call for action statement, which in a few lines identifies a number of critical problems, explains why there is a need to act, and suggests what needs to be done. The call for action is: Some areas of software engineering today suffer from immature practices. Specific problems include: • The prevalence of fads more typical of the fashion industry than an engineering discipline. • The lack of a sound, widely accepted theoretical basis. • The huge number of methods and method variants, with differences little understood and artificially magnified.

A thinking framework in the form of an actionable kernel.

Proton and fluorine magnetic resonance spectra have been observed in twelve liquid polysubstituted ethanes over temperature ranges of 2500 to 450 0 K6 in each Of these compounds, reorientations about the C-C bond are fast enough to yield high resolution nmr spectra which are averages of the three rotational isomers. The change in the proportions of the isomers with temperature is large enough for CHC1aCHCla, CHClgCHF&, CFgClCFCl 3 , CHCl2CHFCl, And CFaBrCFBrCl, and also CFCl 2 CHCig for which JHF> has been reported, to permit a least-squares type analysis of the averaged shifts (Vk> and coupling constants (3) with a high-speed digital computer. The latter evaluates the physical parameters, three or five depending upon molecular symmetry, which govern the temperature dependence of and (J). These parameters, in our approximation, are the values of the spectral quantity in question for each of the "rotamers, and the relative energies aZ of the latter. This procedure could not be applied to CH 2 CH 2 (CO0), CflraCIIBr, HH CH20CH 2 Cl and CHa2CH2Br for which LE is sufficiently small that (J is virtually temperature independent. However, an approximation was developed The nmr methods developed appear to be very versatile in principle.With improved instrumentation, higher quality data, and a better understanding of the factors which can affect the results, nmr may well be the best approach to 4X for liquid or even gaseous molecules containing hydrogen or fluorine.Certainly, such studies are useful in establishing the dependence of nmr parameters upon rotational configuration.

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This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 216.165.95.74 On: Wed, 03 Dec 2014 17:54:41R H E 0 -0 P TIC ALP R 0 PER TIE S 0 F PVC HOM 0 POL Y MER F I L M S 4123 by a combination of stress and temperature acting in a mutually interchangeable way. If this is a correct point of view, the glass transition must then be regarded not as a temperature, but as a phenomenon which is a function of temperature, stress level, and time,To=G (T, u, t).( 1)This clearly has important implications for the theory of the glass transition, and provides a new experimental approach to its study. This is not a completely new idea, since Bryant 12 has previously interpreted drawing in modacrylic fibers (acrylonitrile/vinyl chloride copolymer) as a stress-induced glass transition. He has interpreted the effects of stress in terms of a free-volume change, produced by the Poisson's ratio effect, together with a critical freevolume criterion for the glass transition. This is related to a similar treatment of the effect of stress on viscoelastic relaxation rates which has been given by Ferry and Stratton.I 3 Bryant's experiments involved the measurement of hysteresis in stress-strain cycles as a means of identifying the glass transition; this type of data seems less satisfactory for interpretation than the creep data obtained in the present investigation. Similar ideas on the relation of stress to the 12 G. M. Bryant, Textile Res. J. 31, 399 (1961). 13 J. D. Ferry and R. A. Stratton, Kolloid-Z. 171,107 (1960). glass transition and yield have also been arrived at independently by Kurtz 14 and Yannas. 15 The effect of stress on the glass transition, and the equivalence of temperature and stress in changing the free volume, has also been discussed in a recent article by Eirich.I 6 The effects of stress and temperature on the glass transition are not precisely identical, however, because stress can be applied in a directional way, whereas temperature is a homogeneous and isotropic property. This means that the effects of multiaxial stresses can be investigated and combined with temperature in different ways in order to produce the yield or cold drawing phenomenon. This seems to be an extremely fruitful area for future research. An investigation of the quantitative relationships between stress and temperature, as they influence the yield phenomenon, is clearly needed. ACKNOWLEDGMENTSAppreciation is expressed to the Kao Soap Co. Ltd. for the financial support of one of the authors (Y.K.) during his stay at Stevens Institute. We also wish to thank the Stauffer Chemical Company for supplying the polymer used in this investigation. 14 s. J. Kurtz, Princeton Univ. (private communication). I.Certain properties of crystalline polymers can be associated with the presence of local defects, e.g., deviations of short segments of the chain from the predominant conformation allied with the crystal structure. General methods are develope...