We propose a new approach for vision based longitudinal and lateral vehicle control which makes extensive use of binocular stereopsis. Longitudinal control --- i.e. maintaining a safe, constant distance from the vehicle in front --- is supported by detecting and measuring the distances to leading vehicles using binocular stereo. A known camera geometry with respect to the locally planar road is used to map the images of the road plane in the two camera views into alignment. Any significant residual image disparity then indicates an object not lying in the road plane and hence a potential obstacle. This approach allows us to separate image features into those lying in the road plane, e.g. lane markers, and those due to other objects. The features which lie on the road are stationary in the scene and appear to move only because of the egomotion of the vehicle. Measurements on these features are used for dynamic update of (a) the camera parameters in the presence of camera vibration and changes in road slope (b) the lateral position of the vehicle with respect to the lane markers. In the absence of this separation, image features due to vehicles which happen to lie in the search zone for lane markers would corrupt the estimation of the road boundary contours. This problem has not yet been addressed by any lane marker based vehicle guidance approach, but has to be taken very seriously, since usually one has to cope with crowded traffic scenes where lane markers are often obstructed by vehicles. Lane markers are detected and used for lateral control, i.e. following the road while maintaining a constant lateral distance to the road boundary. For that purpose we model the road and hence the shape of the lane markers as clothoidal curves, the curvatures of which we estimate recursively along the image sequence. These curvature estimates also provide desirable look-ahead information for a smooth ride in the car.
The chemistry of titanocene bisborane complexes Cp2Ti(HBcat')2 (1a−g) (HBcat' = catecholborane or a substitued catecholborane) and monoborane complexes Cp2Ti(HBcat')(L) (2−4) (L = PMe3, PhSiH3, or PhCCPh) is reported. These complexes are unusual σ-complexes. The B−H bond in the catecholborane of 1 acts as a two-electron-donor ligand. The 4-tert-butyl version 1a was studied in depth and underwent ligand substitution reactions with PMe3, CO, PhSiH3, and PhCCPh. The products of the reaction of 1a with PMe3 and PhSiH3 are the novel monoborane σ-complexes Cp2Ti(HBcat')(PMe3) (2a; HBcat' = HBO2C6H3-4-t-Bu) and Cp2Ti(HBcat')(PhSiH3) (3; HBcat' = HBO2C6H3-4-t-Bu), in which the catecholborane remains a two-electron-donating ligand. Reaction with CO formed Cp2Ti(CO)2. Reaction with PhCCPh formed Cp2Ti(HBcat')(PhCCPh) (4; HBcat' = HBO2C6H3-4-t-Bu), which was observed in solution and reductively eliminated the vinyl boronate ester (Ph)(Bcat')CC(Ph)(H). The rates for the reactions of 1a with these substrates showed a first-order dependence on the concentration of 1a and a zero-order dependence on the concentrations of both the departing HBcat' and the incoming ligand. The substitution reaction proceeded at the same rate ((3.8 ± 0.3) × 10-4) regardless of the identity of the incoming ligand. The entropy of activation was +30 ± 5 eu. These data are consistent with a dissociative substitution mechanism for the reaction of 1a with these substrates. The ΔH⧧ value of 25 ± 3 kcal mol-1 for these reactions provides an upper limit for the strength of the borane−metal interaction. Electronic effects on the reaction rate support a bonding model involving back-donation from titanium to the borane, and the unusual steric effects allow a proposal for the geometric changes that occur upon formation of the transition state.
The single-operation deracemization of 3H indolines and tetrahydroquinolines is described. An asymmetric redox approach was employed, in which a phosphoric acid catalyst, oxidant, and reductant are present in the reaction mixture. The simultaneous presence of both oxidant and reductant was enabled by phase separation and resulted in the isolation of highly enantioenriched starting materials in high yields.
The principal goals of this project are to develop advanced electrochemical emission spectroscopic (EES) methods for monitoring the corrosion of carbon steel in simulated DOE liquid waste and to develop a better understanding of the mechanisms of the corrosion of metals (e.g. iron, nickel, and chromium) and alloys (carbon steel, low alloy steels, stainless steels) in thes e environments. During the first two years of this project, significant advances have been made in developing a better understanding of the corrosion of iron in aqueous solutions as a function of pH, on developing a better understanding of the growth of passive films on metal surfaces, and on developing EES techniques for corrosion monitoring. This report summarizes work on beginning the third year of the 3-year project.
New rhodium and iridium complexes supported by the phenyl-substituted PNP pincer ligand PNPPhH (HN(2-PPh2-4-Me-C6H3)2) (1) were synthesized. The reaction of 2 equiv. of 1 with [(COD)IrCl]2 afforded the coordination complex [(PNPPhH)Ir(COD)]Cl (2) featuring hydrogen bonding between the N–H group and the chloride anion, as characterized by NMR spectroscopy and X-ray crystallography. Reaction of 1 with [(COE)2IrCl]2 or [(COE)2RhCl]2 in benzene provided a mixture of complexes including (PNPPhH)MHCl2 (M = Ir (4), M = Rh (7)) and (PNP)M(COE) (M = Ir (5), M = Rh (8)). Alkene complexes of the type (PNPPh)M(L) (M = Ir, L = COD (3) and COE (5); M = Rh, L = COE (8) and L = ethylene (9)) were synthesized by reaction of (PNPPh)Li with the appropriate alkene chloride complexes. Reactions of silanes with 5, 8 or 9 produced silyl hydride complexes (PNPPh)MH(SiR3) (M = Ir, R = Ph (16) and R = Et (17); M = Rh, R = Ph (18), Et (19) and Ph2Cl (20)) via Si–H oxidative addition. The JSiH coupling constants for rhodium complexes 18, 19 and 20 were determined to be ca. 35 Hz, while iridium complexes 16 and 17 exhibited coupling constants less than 10 Hz. X-Ray crystal structures of 16 and 18 reveal isostructural complexes featuring a trigonal bipyramidal geometry about iridium with a mer binding of the PNPPh ligand. A hydride ligand, located from the Fourier map for 18, has a short contact of 1.83(3) Å with the silicon atom. Oxidative addition of iodomethane to 5 and 8 afforded (PNPPh)M(Me)(I)(THF) (M = Rh (14), M = Ir (12)), respectively. Arene C–H activation upon thermolysis of 12 in benzene produced (PNPPh)M(Ph)(I)(THF). Iridium silyl iodide complexes (PNPPh)IrI(SiR3) (SiR3 = SiPh3 (21), SiH2Mes (22) and SiH2Xyl (23)) resulted from addition of organosilanes to 12, via elimination of CH4.
