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The goal of Inductive Logic Programming (ILP) is to find a hypothesis that explains a set of examples in the context of some pre-existing background knowledge. Until recently, most research on ILP targeted learning definite logic programs. This thesis constitutes the first comprehensive work on learning answer set programs, introducing new learning frameworks, theoretical results on the complexity and generality of these frameworks, algorithms for learning ASP programs, and an extensive evaluation of these algorithms. Although there is previous work on learning ASP programs, existing learning frameworks are either brave -- where examples should be explained by at least one answer set -- or cautious where examples should be explained by all answer sets. There are cases where brave induction is too weak and cautious induction is too strong. Our proposed frameworks combine brave and cautious learning and can learn ASP programs containing choice rules and constraints. Many applications of ASP use weak constraints to express a preference ordering over the answer sets of a program. Learning weak constraints corresponds to preference learning, which we achieve by introducing ordering examples. We then explore the generality of our frameworks, investigating what it means for a framework to be general enough to distinguish one hypothesis from another. We show that our frameworks are more general than both brave and cautious induction. We also present a new family of algorithms, called ILASP (Inductive Learning of Answer Set Programs), which we prove to be sound and complete. This work concerns learning from both non-noisy and noisy examples. In the latter case, ILASP returns a hypothesis that maximises the coverage of examples while minimising the length of the hypothesis. In our evaluation, we show that ILASP scales to tasks with large numbers of examples finding accurate hypotheses even in the presence of high proportions of noisy examples.

Infrared overtone absorption spectra of vapour phase methyl fluoride, and methyl bromide-d3 have been measured and these results, combined with existing near infrared and visible spectra, have been analysed in terms of a model of local mode C-H/D stretching vibrations including the effects of Fermi resonances with the overtones of the C-H/D bending modes. Comparable analyses of CH3Cl, CH3Br, CH3I and CHD2Cl, up to 6 quanta of C-H stretching, improve earlier studies through the more quantitative treatment of the stretch/bend interactions. The empirical vibration frequencies, anharmonicity constants and vibration interaction constants determined in these analyses are found to be in good agreement with literature ab initio results. In particular discrepancies between the effective empirical Fermi resonance parameters and the theoretical normal coordinate cubic force constants are rationalised by consideration of higher order effects within the framework of the traditional perturbation theory treatment. An important feature of this work is the development of the understanding of the relationship between the local mode and normal mode models of coupled X-H stretching vibrations. In particular the simple harmonically coupled local mode model has been extended to include the effects of anharmonic interactions. Explicit relationships have been derived between this extended local mode parameter set and those of the conventional mode description for the X-H stretching vibrations of ammonia, methane, allene, ethylene and benzene type systems. The complete general harmonic force field of methyl fluoride has been recalculated using the most recent literature frequency, Coriolis and centrifugal distortion data for 12CH3F, 13CH3F, 12CD3F, 12CHD2F and 12CH2DF. The anharmonic corrections applied to the observed frequency data are considered to be more realistic than those used hitherto. There is excellent overall agreement between the fitted force constants and the highest quality ab initio force field currently available.

Sunflowers (Helianthus annuus L.) rank third in acreage among the world's oil crops. Approximately 185, 000 ha of sunflowers are grown in South Dakota each year. Despite sunflower's economic importance, few herbicides are available for use in the crop and many of the herbicides commonly used on soybeans (Glycine Max (L.) Merr.) and corn (Zea mays L.) will harm sunflowers. Therefore, weed infestations are a major factor confronting the sunflower grower. Wild mustard (Brassica kaber (DC.) Wheeler) and green foxtail (Setaria viridis (L.) Beauv) commonly infest sunflower fields in North and South Dakota. According to a survey in North Dakota, 94% of the sunflower fields contained green foxtail and 75% contained wild mustard. Wild mustard is very competitive and one wild mustard plant/m of crop row reduces yield. EPTC (S-ethyl dipropylthiocarbamate), trifluralin (a, a,a-trifluoro-2, 6-dinitro-N-N-dipropyl-p-toluidine), and chloramben (3-amino-2, 5-dichlorobenzoic acid) are labeled for control of annual grasses and certain broadleaf weeds in sunflower fields. Although herbicides are available for grass control, more effective ones are needed to control broadleaf weeds in sunflower fields. A postemergence herbicide would significantly aid weed control and could be used in conservation tillage.

The molecular structures of the Si2HX, Si2Li2, SiGeHLi and C2H2 species (where X= H, Li, F and Cl) were studied. All of these species have more than one isomeric form. The critical points on the potential energy surfaces of the Si2HX, Si2Li2and C2H2 species and the minima on the SiGeHLi surface were located. The full six-dimensional potential energy surface (PES) of the Si2Li2 molecule was calculated (for the first time) using the CCSD(T)-F12a/cc-pVTZ-F12 level of theory. The core-valence, zero-point energy and relativistic corrections for the Si2HLi and Si2Li2 species were calculated. Additionally, the electron affinity and Li+ /H+ binding energies for the Si2HLi and Si2Li2 structures were investigated. Furthermore, the anharmonic vibrational-rotational properties for the Si2HLi and Si2Li2 structures were calculated using second-order perturbation theory. The recently developed CCSD(T)-F12a method with the cc-pVTZ-F12 basis set was employed to obtain geometries and relative energies (for the Si2HLi, Si2HF, Si2HCl and Si2Li2 structures) and vibrational frequencies (for the Si2H2 and Si2Li2 structures). The CCSD(T) method with the cc-pVXZ, aug-cc-pVXZ and aug-cc-pV(X+d)Z basis sets, CCSD(T)-F12a/cc-pVXZ (where X=2-4) and the B3LYP/6-311+G(d) levels of theory were also used. Comparison was made of the geometric properties and vibrational frequencies calculated at the different levels of theory. The calculated geometric properties for all the studied species and vibrational frequencies (for the Si2H2 structures) show good agreement with the experimental and theoretical literature. The PES of Si2Li2 was used to perform large scale variational vibrational calculations using the WAVR4 program. The first 2400 totally symmetric energy levels were calculated. The low-lying energy levels were qualitatively correct. Conclusive assignments of the vibrational modes of the Si2Li2 structures were made for the eleven lowest lying energy levels.