6,964 research outputs found
Active vibration control of rotating beam with moving mass using piezoelectric actuator
The robotic arm carrying a moving end effector can be modeled as a rotating beam with moving mass. Active vibration control of rotating beam with moving mass using piezoelectric actuator is presented. Simply supported beam and cantilevered beam are considered in this studying. The equations of the system are derived by Lagrange’s equation with the assumed mode method. The linear classical optimal control algorithm with displacement-velocity feedback is used to determine the control voltage. The numerical simulations reveal that the transverse displacements of the beam can be effectively reduced by the actuators. The effect of rotational speed and acceleration to the dynamic responses of the beam are also investigated
Monolayer Molybdenum Disulfide Nanoribbons with High Optical Anisotropy
Two-dimensional Molybdenum Disulfide (MoS2) has shown promising prospects for
the next generation electronics and optoelectronics devices. The monolayer MoS2
can be patterned into quasi-one-dimensional anisotropic MoS2 nanoribbons
(MNRs), in which theoretical calculations have predicted novel properties.
However, little work has been carried out in the experimental exploration of
MNRs with a width of less than 20 nm where the geometrical confinement can lead
to interesting phenomenon. Here, we prepared MNRs with width between 5 nm to 15
nm by direct helium ion beam milling. High optical anisotropy of these MNRs is
revealed by the systematic study of optical contrast and Raman spectroscopy.
The Raman modes in MNRs show strong polarization dependence. Besides that the
E' and A'1 peaks are broadened by the phonon-confinement effect, the modes
corresponding to singularities of vibrational density of states are activated
by edges. The peculiar polarization behavior of Raman modes can be explained by
the anisotropy of light absorption in MNRs, which is evidenced by the polarized
optical contrast. The study opens the possibility to explore
quasione-dimensional materials with high optical anisotropy from isotropic 2D
family of transition metal dichalcogenides
Spatially resolved pump-probe study of single-layer graphene produced by chemical vapor deposition
Carrier dynamics in single-layer graphene grown by chemical vapor deposition
(CVD) is studied using spatially and temporally resolved pump-probe
spectroscopy by measuring both differential transmission and differential
reflection. By studying the expansion of a Gaussian spatial profile of carriers
excited by a 1500-nm pump pulse with a 1761-nm probe pulse, we observe a
diffusion of hot carriers of 5500 square centimeter per second. We also observe
that the expansion of the carrier density profile decreases to a slow rate
within 1 ps, which is unexpected. Furthermore, by using an 810-nm probe pulse
we observe that both the differential transmission and reflection change signs,
but also that this sign change can be permanently removed by exposure of the
graphene to femtosecond laser pulses of relatively high fluence. This indicates
that the differential transmission and reflection at later times may not be
directly caused by carriers, but may be from some residue material from the
sample fabrication or transfer process.Comment: 9 pages, 3 figure
New Supernova Candidates from SDSS-DR7 of Spectral Survey
The letter presents 25 discovered supernova candidates from SDSS-DR7 with our
dedicated method, called Sample Decrease, and 10 of them were confirmed by
other research groups, and listed in this letter. Another 15 are first
discovered including 14 type Ia and one type II based on Supernova
Identification (SNID) analysis. The results proved that our method is reliable,
and the description of the method and some detailed spectra analysis procedures
were also presented in this letter.Comment: 6 pages, 3 figure
Building quantum neural networks based on swap test
Artificial neural network, consisting of many neurons in different layers, is
an important method to simulate humain brain. Usually, one neuron has two
operations: one is linear, the other is nonlinear. The linear operation is
inner product and the nonlinear operation is represented by an activation
function. In this work, we introduce a kind of quantum neuron whose inputs and
outputs are quantum states. The inner product and activation operator of the
quantum neurons can be realized by quantum circuits. Based on the quantum
neuron, we propose a model of quantum neural network in which the weights
between neurons are all quantum states. We also construct a quantum circuit to
realize this quantum neural network model. A learning algorithm is proposed
meanwhile. We show the validity of learning algorithm theoretically and
demonstrate the potential of the quantum neural network numerically.Comment: 10 pages, 13 figure
Epigenetic Alterations in Anesthesia-Induced Neurotoxicity in the Developing Brain
Before birth and early in life, the developing brain is particularly sensitive to environmental and pharmacological influences. Increasing experimental evidence suggests that an association exists between exposure to anesthesia during a vulnerable period of brain development and subsequent poor neurodevelopmental outcomes. However, the mechanisms underlying this association are not fully understood. Epigenetics, broadly defined as the regulation of gene expression without alterations of DNA sequence, has become a field of tremendous interest in neuroscience. In recent years, a growing body of literature suggests that anesthesia-induced long-term changes in gene transcription and functional deficits in learning and behavior later in life are mediated via epigenetic modifications. This brief review provides an overview of epigenetic mechanisms and highlights the emerging roles played by epigenetic dysfunctions in the processes of anesthesia-induced neurotoxicity in the developing brain. Epigenetic targeting of DNA methyltransferases and/or histone deacetylases may have some therapeutic value. Epigenetics may lead to the identification of novel markers that contribute toward considerable translational significance in the field of neuroprotection
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