Study of ultrafast Rabi flopping in colloidal quantum dots at room temperature

The interaction between high-intensity ultrashort optical pulses and materials has led to a number of fascinating optical phenomena, including Rabi flopping and self-induced transparency. Until now, there have been few reports on ultrashort coherent pulse propagation and reshaping in semiconductor materials. Here we investigate Rabi flopping and Rabi splitting in colloidal quantum dots with Fabry-Perot cavity of SU8/Si. The Rabi flopping phenomenon is monitored via the pump-probe differential reflection spectroscopy. A high excitation power reshapes the temporal oscillations so that the fast Fourier transform spectra display several peaks. The photoluminescence spectrum by continuous-wave excitation splits under a proper incident angle, and the splitted photoluminescence spectrum is generally consistent with the amplitude of differential reflectivity as function of wavelength. These results demonstrate that both of the temporal oscillations and the splitting of the continuous-wave excited photoluminescence spectra are due to strong coupling between colloidal quantum dots and the Fabry-Perot cavity.

Analysis of changes in the angular velocity of the crankshaft of the marine engine for diagnosing the wear and location the failure of the fuel injection system

The combustion process can be simply described as periodic explosions in a cylinder with its frequency dependent on the number of cylinders and the rotational speed of the shaft. In practice, uniformity of combustion parameters in every cylinder is almost impossible. Due to this fact, instantaneous angular acceleration does not remain the same at the ends of the crankshaft. These observations formed the basis for the investigation of the instantaneous angular speed of the crankshaft ends. To investigate the influence of the failure behavior of the fuel systems during a shaft's rotational movement, a series of experiments were planned. For the simulations, a medium-speed marine engine driving electro generator was selected. The failure simulation was based on the installation of clogged spray holes, draining of part of fuel dose from high-pressure pump and decreasing of injection pressure by a lower tension of the injector spring. The results of measurement were processed and analyzed through a comparison of the fast Fourier transform spectra. As a general conclusion, a difference between general harmonics order of magnitudes was detected.

Synchrotron spectroscopy of the CSH-bending and CH3-rocking bands of methyl mercaptan

The CSH-bending and CH3-rocking infrared bands of CH3SH have been investigated in Fourier transform spectra recorded at 0.001 cm−1 resolution employing synchrotron radiation at the Canadian Light Source in Saskatoon. The relative band strengths and structures are quite different from those of the CH3OH methanol analogue, with the CSH bend being very weak and both the in-plane and out-of-plane CH3 rocks being strong with intensities greater than the C–S stretch. The CSH bend has parallel a-type character with no detectable b-type component. The out-of-plane CH3 rock is a purely c-type perpendicular band, whereas the in-plane rock is of mixed a/b character. Sub-bands have been assigned for A and E torsional species up to about K = 10 for each vibrational mode, providing upper-state term values from which K-reduced substate origins were determined. For the CSH bend, the origins follow the customary oscillatory torsional pattern as a function of K with a sharply reduced amplitude of 0.362 cm−1 compared to the 0.653 cm−1 for the ground state. The torsional energy curves for the out-of-plane rock are also well-behaved but have inverted ordering of the A–E torsional splitting components and a larger amplitude of 1.33 cm−1. In contrast, the substate origins for the in-plane rock are scattered over a range of about 2 cm−1 without clear oscillatory structure. Several instances of coupling among the lower modes and the ground state via resonances between accidentally near-degenerate levels have been observed and characterized. Ab initio calculations are found to give a good representation of the frequency and relative intensity patterns for the lower vibrational modes.

Quantity of Hydrophobic Functional CH-Groups – Decisive for Soil Water Repellency Caused by Digestate Amendment

Anaerobic digestates are used as organic fertilizers; however, they are suspected to interfere negatively with soils. To investigate the relevance of the anaerobic digestates composition on potential wettability and contact angle of the soil, we mixed in a laboratory experiment 30 m³ ha-1 of anaerobic digestates derived from mechanically pre-treated substrates from maize and sugar beet with a homogenized Cambic Luvisol. Fourier transform infrared-spectra and diffuse reflectance infrared Fourier transform-spectra of particle intact and finely ground soilanaerobic digestates-mixtures were analyzed to determine the quantities of hydrophobic functional groups in the soil-anaerobic digestates-mixtures that are used here as an indicator for the potential hydrophobicity. The anaerobic digestates application increased the amount of hydrophobic functional groups of the mixtures and reduced the wettability of the soil. However, for intact particle samples an up to threefold higher amount of hydrophobic groups was found as compared to the finely ground ones, indicating a dilution effect of mechanical grinding on the effectivity of the organic matter that is presumably located as a coating on mineral soil particles. For the particle intact samples, the intensity of hydrophobic functional groups bands denoting hydrophobic brickstones in organic matter is indicative for the actual wettability of the soil-anaerobic digestates-mixtures.