Rensselaer Polytechnic Institute

About: Rensselaer Polytechnic Institute is a education organization based out in Troy, New York, United States. It is known for research contribution in the topics: Terahertz radiation & Population. The organization has 19024 authors who have published 39922 publications receiving 1414699 citations. The organization is also known as: RPI & Rensselaer Institute.

First-principles Raman spectra of MoS2, WS2 and their heterostructures

Abstract: Raman spectra of MoS2, WS2, and their heterostructures are studied by density functional theory. We quantitatively reproduce existing experimental data and present evidence that the apparent discrepancy between intensity ratios observed experimentally can be explained by the high sensitivity of the Raman-active modes to laser polarization. Furthermore, MoS2/WS2 heterostructures up to four layers are considered in every possible combination and stacking order. Each heterostructure configuration possesses a unique Raman spectrum in both frequency and intensity that can be explained by changes in dielectric screening and interlayer interaction. The results establish a set of guidelines for the practical experimental identification of heterostructure configurations.

Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars

Abstract: The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150–300 parts per billion by weight (ppbw)) and C2 to C4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles.

Field-effect transistors based on few-layered α-MoTe2

Abstract: Here we report the properties of field-effect transistors based on a few layers of chemical vapor transport grown α-MoTe2 crystals mechanically exfoliated onto SiO2. We performed field-effect and Hall mobility measurements, as well as Raman scattering and transmission electron microscopy. In contrast to both MoS2 and MoSe2, our MoTe2 field-effect transistors are observed to be hole-doped, displaying on/off ratios surpassing 106 and typical subthreshold swings of ∼140 mV per decade. Both field-effect and Hall mobilities indicate maximum values approaching or surpassing 10 cm2/(V s), which are comparable to figures previously reported for single or bilayered MoS2 and/or for MoSe2 exfoliated onto SiO2 at room temperature and without the use of dielectric engineering. Raman scattering reveals sharp modes in agreement with previous reports, whose frequencies are found to display little or no dependence on the number of layers. Given that MoS2 is electron-doped, the stacking of MoTe2 onto MoS2 could produce amb...

An embedded wavelet video coder using three-dimensional set partitioning in hierarchical trees (SPIHT)

Abstract: The SPIHT (set partitioning in hierarchical trees) algorithm by Said and Pearlman (see IEEE Trans. on Circuits and Systems for Video Technology, no.6, p.243-250, 1996) is known to have produced some of the best results in still image coding. It is a fully embedded wavelet coding algorithm with precise rate control and low complexity. We present an application of the SPIHT algorithm to video sequences, using three-dimensional (3D) wavelet decompositions and 3D spatio-temporal dependence trees. A full 3D-SPIHT encoder/decoder is implemented in software and is compared against MPEG-2 in parallel simulations. Although there is no motion estimation or compensation in the 3D SPIHT, it performs measurably and visually better than MPEG-2, which employs complicated motion estimation and compensation.

A Modified Quadtree Approach To Finite Element Mesh Generation

Abstract: By allowing the use of quadrants with cut corners, this modeling technique overcomes some of the drawbacks of standard quadtree encoding for finite element mesh generation.