32,173 research outputs found
A data driven deep neural network model for predicting boiling heat transfer in helical coils under high gravity
In this article, a deep artificial neural network (ANN) model has been proposed to predict the boiling heat transfer in helical coils under high gravity conditions, which is compared with experimental data. A test rig is set up to provide high gravity up to 11 g with a heat flux up to 15100 W/m 2 and the mass velocity range from 40 to 2000 kg m −2 s −1. In the current work, a total 531 data samples have been used in the ANN model. The proposed model was developed in a Python Keras environment with Feed-forward Back-propagation (FFBP) Multi-layer Perceptron (MLP) using eight features (mass flow rate, thermal power, inlet temperature, inlet pressure, direction, acceleration, tube inner surface area, helical coil diameter) as the inputs and two features (wall temperature, heat transfer coefficient) as the outputs. The deep ANN model composed of three hidden layers with a total number of 1098 neurons and 300,266 trainable parameters has been found as optimal according to statistical error analysis. Performance evaluation is conducted based on six verification statistic metrics (R 2, MSE, MAE, MAPE, RMSE and cosine proximity) between the experimental data and predicted values. The results demonstrate that a 8-512-512-64-2 neural network has the best performance in predicting the helical coil characteristics with (R 2=0.853, MSE=0.018, MAE=0.074, MAPE=1.110, RMSE=0.136, cosine proximity=1.000) in the testing stage. It is indicated that with the utilisation of deep learning, the proposed model is able to successfully predict the heat transfer performance in helical coils, and especially achieved excellent performance in predicting outputs that have a very large range of value differences
Modelling flan wear of carbide tool insert in metal cutting
In this paper theoretical and experimental studies are carried out to investigate the intrinsic relationship between tool flank wear and
operational conditions in metal cutting processes using carbide cutting inserts.Anewflank wear rate model, which combines cutting mechanics
simulation and an empirical model, is developed to predict tool flank wear land width. A set of tool wear cutting tests using hard metal coated
carbide cutting inserts are performed under different operational conditions. The wear of the cutting inset is evaluated and recorded using
Zygo New View 5000 microscope. The results of the experimental studies indicate that cutting speed has a more dramatic effect on tool life
than feed rate. The wear constants in the proposed wear rate model are determined based on the machining data and simulation results. A
good agreements between the predicted and measured tool flank wear land width show that the developed tool wear model can accurately
predict tool flank wear to some extent
Direct laser acceleration of electrons in free-space
Compact laser-driven accelerators are versatile and powerful tools of
unarguable relevance on societal grounds for the diverse purposes of science,
health, security, and technology because they bring enormous practicality to
state-of-the-art achievements of conventional radio-frequency accelerators.
Current benchmarking laser-based technologies rely on a medium to assist the
light-matter interaction, which impose material limitations or strongly
inhomogeneous fields. The advent of few cycle ultra-intense radially polarized
lasers has materialized an extensively studied novel accelerator that adopts
the simplest form of laser acceleration and is unique in requiring no medium to
achieve strong longitudinal energy transfer directly from laser to particle.
Here we present the first observation of direct longitudinal laser acceleration
of non-relativistic electrons that undergo highly-directional multi-GeV/m
accelerating gradients. This demonstration opens a new frontier for direct
laser-driven particle acceleration capable of creating well collimated and
relativistic attosecond electron bunches and x-ray pulses
Inhibition of Rice Germination by Ustiloxin A Involves Alteration in Carbon Metabolism and Amino Acid Utilization
Ustiloxins are the main mycotoxin in rice false smut, a devastating disease caused by Ustilaginoidea virens. A typical phytotoxicity of ustiloxins is strong inhibition of seed germination, but the physiological mechanism is not clear. Here, we show that the inhibition of rice germination by ustiloxin A (UA) is dose-dependent. The sugar availability in UA-treated embryo was lower while the starch residue in endosperm was higher. The transcripts and metabolites responsive to typical UA treatment were investigated. The expression of several SWEET genes responsible for sugar transport in embryo was down-regulated by UA. Glycolysis and pentose phosphate processes in embryo were transcriptionally repressed. Most of the amino acids detected in endosperm and embryo were variously decreased. Ribosomal RNAs for growth was inhibited while secondary metabolites salicylic acid was also decreased under UA. Hence, we propose that the inhibition of seed germination by UA involves the block of sugar transport from endosperm to embryo, leading to altered carbon metabolism and amino acids utilization in rice plants. Our analysis provides a framework for understanding of the molecular mechanisms of ustiloxins on rice growth and in pathogen infection
X-Ray Flares of Gamma-Ray Bursts: Quakes of Solid Quark Stars?
We propose a star-quake model to understand X-ray flares of both long and
short Gamma-ray bursts (GRBs) in a solid quark star regime. Two kinds of
central engines for GRBs are available if pulsar-like stars are actually
(solid) quark stars, i.e., the SNE-type GRBs and the SGR-type GRBs. It is found
that a quark star could be solidified about 10^3 to 10^6 s later after its
birth if the critical temperature of phase transition is a few MeV, and then a
new source of free energy (i.e., elastic and gravitational ones, rather than
rotational or magnetic energy) could be possible to power GRB X-ray flares.Comment: 8 pages, latex file. 2 figures. To appear in Science in China Series
A method to widen the scattering bandwidth of closed cylindrical active coated nano particles
Plane wave scattering from two closely spaced, closed cylindrical active coated nano particles (CNPs), which have slightly different resonance frequencies, is studied numerically. Although the distance between them is only 0.4λ, the scattering cross-section(SCS) background value of this two-CNP system is increased 5dB when r2 = 15.1 nm and the 3dB SCS bandwidth is 599.95THz-600.1THz, which is a substantially wider working bandwidth near the SCS peak than the one associated with either single CNP, i.e. 600.01THz-600.1THz. © 2013 IEEE
Numerical Study of the Near-Field and Far-Field Properties of Active Open Cylindrical Coated Nanoparticle Antennas
A very electrically small, active open cylindrical coated nanoparticle model is constructed, and its electromagnetic properties are investigated in the visible frequency band. Its optical response under both planewave and electric dipole antenna excitations shows very strong dipole behavior at its lowest resonance frequency. The scattering cross section at that dipole resonance frequency is increased by more than +50 dBsm for the planewave excitation. When the open structure is excited by a small current (I0 = 1 × 10−3 A) driven dipole antenna, the maximum radiated power of the composite nanoantenna can be increased by +83.35 dB over its value obtained when the dipole antenna radiates alone in free space. The behaviors under various locations and orientations of the dipole are explored. Dipole orientations along the cylinder axis and symmetric locations of the dipole produced the largest radiated power enhancements. © 2011, IEEE. All rights reserved
Detailed performance characteristics of vertically polarized, cylindrical, active coated nano-particle antennas
The electromagnetic properties of active cylindrical coated nano-particle antennas are investigated. It is demonstrated that the active cylindrical coated nano-particle, whether illuminated by a plane wave or an electric Hertzian dipole (EHD) (small current) element, acts as a strong dipole radiator at its resonant frequency. It is shown that the plane wave scattering cross section could be increased by about 40 dBsm, and the maximum peak of the power radiated by an EHD element could be increased more than 65 dB in the presence of the active nano-particle over its value when radiating into free space. An array, constructed with four active cylindrical coated nano-particles and excited by an EHD element located at or near its center is also studied. Large directivity values, more than 8 dB, are obtained for particular array configurations and EHD locations. © 2012 by the American Geophysical Union
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