Abstract-We propose a real-time method for odometry and mapping using range measurements from a 2-axis lidar moving in 6-DOF. The problem is hard because the range measurements are received at different times, and errors in motion estimation can cause mis-registration of the resulting point cloud. To date, coherent 3D maps can be built by off-line batch methods, often using loop closure to correct for drift over time. Our method achieves both low-drift and low-computational complexity without the need for high accuracy ranging or inertial measurements. The key idea in obtaining this level of performance is the division of the complex problem of simultaneous localization and mapping, which seeks to optimize a large number of variables simultaneously, by two algorithms. One algorithm performs odometry at a high frequency but low fidelity to estimate velocity of the lidar. Another algorithm runs at a frequency of an order of magnitude lower for fine matching and registration of the point cloud. Combination of the two algorithms allows the method to map in real-time. The method has been evaluated by a large set of experiments as well as on the KITTI odometry benchmark. The results indicate that the method can achieve accuracy at the level of state of the art offline batch methods.

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To rationalize the marked difference in the energy conversion efficiency of dye sensitized solar cells (DSSCs) based on organic dyes 1 and 2 different only in their p spacer, density functional theory (DFT) and time-dependent DFT calculations of the geometries, electronic structures and absorption spectra of the organic dyes before and after binding to titanium oxide were carried out. These enable us to determine factors such as dipole moments associated with the open-circuit photovoltage (V oc ), and to quantify parameters such as the light harvesting efficiency, the electron injection efficiency associated with the short-circuit photocurrent density (J sc ). The results reveal that compared to 2 with a thiazole spacer, 1 with a thiophene spacer could cause a red shift of the absorption spectrum, increase the oscillator strength and improve the driving force for electron injection, thus leading to the larger J sc , in good agreement with experimental data. As for V oc , our results stress that apart from the generally emphasized vertical dipole moment of the dyes pointing outward from the semiconductor surface, the number of photoinjected electrons from the dye to the semiconductor is also crucial to obtain high performance dyes with high V oc . After justifying the reliability of the quantum-chemical methods, we designed another four dyes with different p spacers to screen more efficient organic dyes. Fortunately, taking 1 as reference, we find that dye 4 with a thienothiophene spacer displays an enhanced J sc and V oc , indicating that it will be a more efficient diarylamine-fluorene-based organic dye used in DSSCs, which will play a theoretical guiding role in the design and synthesis of new organic dyes.

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The molecular geometries, infrared vibrational spectra, and thermodynamic properties of octanitrocubane (ONC) are calculated using the density functional theory (DFT) method at the B3LYP/6-31G* level. The IR frequency scaling factor 0.9501 suitable for polynitrocubanes is obtained at the B3LYP/6-31G* level, and the calculated IR frequencies of ONC are scaled. The accurate heat of formation 726.47 kJ/mol of ONC in gas phase is obtained via designed isodesmic reaction in which the cubane cage skeleton has been kept. The sublimation enthalpy, density, and heat of formation for ONC crystal are also calculated, and they are 220.63 kJ/mol, 2.189 g/cm3, and 505.84 kJ/mol, respectively. In addition, the estimated detonation velocity and detonation pressure of ONC are 10.26 mm/ms and 520.86 kbar, respectively. Finally, the pyrolysis mechanism of ONC is studied using various theoretical methods, i.e., MP2, DFT, and selected MINDO/3 semiempirical MO, based on the unrestricted Hartree–Fock model. The calculated results show that the pyrolysis initiation reaction of ONC, i.e., rate-controlling step, is to form a diradical by the single C–C bond breaking in the cube. The second C–C bond breaking is easily followed to form a nitrocyclooctatetraene. The calculated activation energy for the pyrolysis initiation reaction of ONC, obtained from B3LYP/6-31G* method, is 155.30 kJ/mol, which this rather large activation energy indicates that ONC is a new type of energetic material with less sensitivity and better thermal stability, and has highly exploitable values.