scholarly journals Characterization of Nucleobases in Broadband Terahertz Spectra from 0.5 to 10 THz with the Air-Biased-Coherent-Detection Technique

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1148 ◽  
Author(s):  
Miao Yu ◽  
Shihan Yan ◽  
Yong-qiang Sun ◽  
Wang Sheng ◽  
Fu Tang ◽  
...  
Keyword(s):  
Low Frequency ◽  
Frequency Region ◽  
Coherent Detection ◽  
Detection Technique ◽  
Terahertz Time Domain Spectroscopy ◽  
High Frequency Region ◽  
Characteristic Absorption ◽  
Thz Range ◽  
Thz Absorption

Terahertz time-domain spectroscopy (THz-TDS) is an effective coherent detection technique for deeply understanding the structures and functions of biomolecules. However, generally not full information in the whole THz range can be obtained due to the limited detection bandwidth (usually less than 5 THz) of the traditional THz-TDS systems. In this paper, effective THz absorption spectra in 0.5–10 THz range of five typical nucleobases of DNA/RNA are characterized with a super broadband THz detection technique, called the air-biased- coherent-detection (THz-ABCD) technique. Few unexpected characteristic absorption peaks appeared in the low-frequency region and meanwhile a series of anticipated characteristic absorption peaks are found in the high-frequency region. The fingerprint spectra of these nucleobases are helpful for further analysis on the vibration and twisting behavior of hydrogen bonds, van der Waals and electrostatic forces etc. between and within DNA/RNA biomolecules.

Electrochemical Corrosion Characterization of As-Cast Mg-7Li Alloy

2012 ◽  
Vol 557-559 ◽  
pp. 64-67
Author(s):  
Jun Gang Li ◽  
Ying Lv ◽  
Hong Wei Wang ◽  
Zhao Jun Zhu ◽  
Zun Jie Wei ◽  
...  
Keyword(s):  
Electrochemical Impedance ◽  
Low Frequency ◽  
Electrochemical Corrosion ◽  
Frequency Region ◽  
X Ray Diffraction ◽  
High Frequency Region ◽  
Anode Dissolution ◽  
Electrochemical Corrosion Behavior ◽  
Capacitive Reactance

The electrochemical corrosion behavior of as-cast Mg-7Li alloy in 3.5wt% NaCl aqueous solution was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical workstation. Results showed that the Ecorr and the Icorr of Mg-7Li alloy were -1.5857V and 2.235×10-4A/cm2, respectively. The cathode process was chiefly the hydrogen evolution reaction, and the corrosion rate of Mg-7Li alloy was mainly controlled by anode dissolution. The corrosion products on the alloy surface consisted of Mg(OH)2, Li2O2 and Al(OH)3. The electrochemical impedance spectroscopy (EIS) of Mg-7Li alloy contained two capacitive loops and one inductive loop. The inductance value increased to 250 ohm•cm-2 with a rise in frequency at low frequency region. The value of capacitive reactance decreased with increasing frequency at medium frequency. The capacitive reactance maintained the value of 50 ohm•cm-2 with increasing frequency at high frequency region.

Anderson-Stuart Model to Analyze AC and DC Conductivity of Lithium Zinc-Silicate Glass / Glass-Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 919-924
Author(s):  
M.S. Jogad ◽  
V.K. Shrikhande ◽  
A.H. Dyama ◽  
L.A. Udachan ◽  
Govind P. Kothiyal
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Low Frequency ◽  
Frequency Region ◽  
Dc Conductivity ◽  
Frequency Range ◽  
High Frequency Region ◽  
Dc Conductivities ◽  
Conductivity Variation ◽  
Different Temperatures

AC and DC conductivities have been measured by using the real (e¢) and imaginary (e¢¢) parts of the dielectric constant data of glass and glass-ceramics (GC) at different temperatures in the rage 297-642K and in the frequency range 100 Hz to 10 MHz. Using Anderson –Stuart model, we have calculated the activation energy, which is observed to be lower than that of the DC conductivity. The analysis for glass/glass-ceramics indicates that the conductivity variation with frequency exhibits an initial linear region followed by nonlinear region with a maximum in the high-frequency region. The observed frequency dependence of ionic conductivity has been analyzed within the extended Anderson–Stuart model considering both the electrostatic and elastic strain terms. In glass/glassceramic the calculations based on the Anderson-Stuart model agree with the experimental observations in the low frequency region but at higher frequencies there is departure from measured data.

SYNTHESIS, PIEZOELECTRIC, DIELECTRIC AND CONDUCTIVITY STUDIES ON Dy2O3 SUBSTITUTED (Bi0.94Na0.94)0.5Ba0.06TiO3 CERAMICS

2011 ◽  
Vol 01 (04) ◽  
pp. 455-464 ◽  
Author(s):  
K. SAMBASIVA RAO ◽  
HAILEEYESUS WORKINEH ◽  
A. SWATHI ◽  
B. S. KALYANI
Keyword(s):  
Low Frequency ◽  
Charge Carrier Concentration ◽  
Frequency Region ◽  
Relaxor Behavior ◽  
Secondary Phases ◽  
X Ray Diffraction ◽  
High Frequency Region ◽  
Pure Perovskite Structure ◽  
Universal Power Law ◽  
Diffraction Patterns

Polycrystalline ( Bi 0.94-x Dy x Na 0.94)0.5 Ba 0.06 TiO 3 ceramics (x = 0, 0.04, and 0.08, designated as BNBT6, BNBT6: 4Dy and BNBT6: 8Dy, respectively) were prepared by conventional high temperature sintering method. The X-ray diffraction patterns show pure perovskite structure with no secondary phases. Lattice parameters and unit cell volumes have decreased due to Dy2O3 substitution. SEM micrographs revealed denser samples (ρrel > 97%) with uniformly distributed grain sizes. The room temperature piezoelectric properties of Dy2O3 substituted sample at x = 0.04 were relatively higher: d33 = 147 pC/N, k p = 28% and Q m = 128. The samples exhibited infinitesimal change in thickness (≈ 15 nm) to an applied voltage of 100 V, which could be utilized in actuator applications. Relaxor behavior and broad dielectric maxima with diffuse phase transition were observed. The value of RT dielectric constant has increased while dielectric loss was decreased due to Dy2O3 substitution. Conductivity in the materials obeys Jonscher's universal power law. The conductivity in the low frequency region is associated with short range translational hopping while it is associated with the reorientational hopping in the high frequency region. The charge carrier concentration term remained constant over the entire temperature range of (30–500°C).

A Thin Cloud Removal Method for Optical Image Based on Improved Homomorphism Filtering

2014 ◽  
Vol 618 ◽  
pp. 519-522
Author(s):  
Guang Yu ◽  
Wen Bang Sun ◽  
Gang Liu ◽  
Mai Yu Zhou
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Component ◽  
Frequency Region ◽  
High Frequency Region ◽  
Filtering Method ◽  
Thin Cloud ◽  
Cloud Removal ◽  
Thin Cloud Removal ◽  
Image Definition

Optical remote image is affected by thin cloud inevitably, which debases image definition. Traditional homomorphism filtering frequently used in thin cloud removing has affect on the cloud in low frequency region, but is not effective for those in high frequency region. An improved homomorphism filtering method is proposed on the basis of statistical characters of image information. Instead of the filtering in frequency field, it isolates the low frequency component of the image representing cloud information with calculating neighborhood average in spatial field. Then, the filtered image is enhanced based on rough set. The experiment results show that the proposed method compared to traditional methods can obtain good results and performs faster.

Analysis of Sound Absorption Properties of Three-Leaf Microperforated Panel Absorbers without a Rigid Backing

2014 ◽  
Vol 937 ◽  
pp. 465-471
Author(s):  
Xiao Ling Gai ◽  
Xian Hui Li ◽  
Rui Wu ◽  
Bin Zhang ◽  
Jun Juan Zhao
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Wide Frequency Range ◽  
Structure Design ◽  
Frequency Region ◽  
Theoretical Development ◽  
Frequency Range ◽  
Absorption Properties ◽  
High Frequency Region ◽  
Energy Dissipated

Microperforated panel (MPP) absorbers have been developed rapidly and used in many fields in recent years. First, based on the Maa’s theory, the theoretical development of MPP is reviewed in this paper. Furthermore, structure design and processing technology of MPP are introduced. Finally, the further development of MPP is discussed. Based on the MPP theory and electro-acoustical equivalent circuit principle, sound absorption properties of three-leaf microperforated panel (TMPP) absorbers without a rigid backing are studied to broaden the sound absorption bandwidth of MPP structure. Simulation results show that TMPP absorbers without a rigid backing have two resonance peaks and the energy dissipated coefficient remains constant in the low frequency range. The resonance frequency moves toward low frequency region with the increasing of the distance, thickness and pore diameter of MPP and moves toward high frequency region with the increasing of the perforation when other parameters keep invariant. The energy dissipated coefficient more than 0.5 over 8 octaves by choosing proper parameters. In conclusion, TMPP absorbers without a rigid backing have good sound absorption properties in a wide frequency range.

Modeling of Perforated Screens or Membrane Using Rigid Frame Porous Models Combined with Thin Membrane Resonance Sound Absorbing Theory

2013 ◽  
Vol 357-360 ◽  
pp. 1206-1211
Author(s):  
Xiao Ling Gai ◽  
Xian Hui Li ◽  
Bin Zhang ◽  
Peng Xie ◽  
Zhi Hui Ma
Keyword(s):  
High Frequency ◽  
Sound Absorption ◽  
Mass Density ◽  
Low Frequency ◽  
Frequency Region ◽  
Thin Membrane ◽  
High Frequency Region ◽  
Rigid Frame ◽  
Membrane Resonance

The sound absorption ability of screen or perforated membrane is studied based on rigid frame porous models combined with thin membrane resonance sound absorbing theory in this paper. Results show that the sound absorption of screen or perforated membrane is better considering the role of membrane than using the rigid frame porous models when the mass density of screen or perforated membrane is smaller. The rigid frame porous model is very accuracy to model the sound absorption ability of screen or perforated membrane when the mass density of membrane is greater. The parameter studies present that the sound absorption peaks move toward low frequency region with the increasing of the depth of air-back cavity, mass density and thickness of screens or perforated membrane and moves toward high frequency region with the increasing of the perforation and perforated radius of screens or perforated membrane when other parameters keep invariant.

scholarly journals Image Fusion Algorithm at Pixel Level Based on Edge Detection

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jiming Chen ◽  
Liping Chen ◽  
Mohammad Shabaz
Keyword(s):  
Edge Detection ◽  
Image Fusion ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Region ◽  
Experimental Comparison ◽  
Fusion Algorithm ◽  
High Frequency Region ◽  
Running Time ◽  
Low Efficiency

In the present scenario, image fusion is utilized at a large level for various applications. But, the techniques and algorithms are cumbersome and time-consuming. So, aiming at the problems of low efficiency, long running time, missing image detail information, and poor image fusion, the image fusion algorithm at pixel level based on edge detection is proposed. The improved ROEWA (Ratio of Exponentially Weighted Averages) operator is used to detect the edge of the image. The variable precision fitting algorithm and edge curvature change are used to extract the feature line of the image edge and edge angle point of the feature to improve the stability of image fusion. According to the information and characteristics of the high-frequency region and low-frequency region, different image fusion rules are set. To cope with the high-frequency area, the local energy weighted fusion approach based on edge information is utilized. The low-frequency region is processed by merging the region energy with the weighting factor, and the fusion results of the high findings demonstrate that the image fusion technique presented in this work increases the resolution by 1.23 and 1.01, respectively, when compared to the two standard approaches. When compared to the two standard approaches, the experimental results show that the proposed algorithm can effectively reduce the lack of image information. The sharpness and information entropy of the fused image are higher than the experimental comparison method, and the running time is shorter and has better robustness.

On the Assignment and Directional Dispersion of Polar Phonon Modes in K3Cu(CN)4 and K3Ag(CN)4

1974 ◽  
Vol 29 (7) ◽  
pp. 1011-1016
Author(s):  
W. Nitsch ◽  
H. J. Falge ◽  
R. Claus
Keyword(s):  
Light Scattering ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Region ◽  
Longitudinal Vibrations ◽  
Phonon Modes ◽  
High Frequency Region ◽  
Single Crystalline ◽  
Scattering Measurements ◽  
Stretching Vibrations

Polar phonon modes in single crystalline K3Cu(CN)4 and K3Ag(CN)4 have been experimentally studied by light scattering. Measurements at 293, 82 and 6 K made possible assignments in the low frequency region from 0 to about 700 cm-1 and the high frequency region from 2030 to about 2100 cm-1 originating from the C≡N stretching vibrations. Directional dispersion due to the anisotropy of K3Cu(CN)4 has been studied and allowed the identification of the transversal and longitudinal vibrations in the high frequency region. IR-reflectivity measurements, partly on the basis of the ATR-method, have been used in order to support the assignments in this region.

WAVE PROPAGATION IN LIPOSOMES

2013 ◽  
Vol 13 (01) ◽  
pp. 1350015
Author(s):  
KE DONG ◽  
GUOXING LU
Keyword(s):  
Wave Propagation ◽  
Wave Speed ◽  
Critical Frequency ◽  
Low Frequency ◽  
Wave Mode ◽  
Frequency Region ◽  
Wave Number ◽  
Rotary Inertia ◽  
High Frequency Region ◽  
Wave Modes

The general behavior of wave propagation in liposomes, including the effect of rotary inertia, is examined in this paper, based on a continuum cylindrical shell model. The disperse curves are obtained by solving an eigenvalue problem. The characteristics of wave propagation in liposomes are described using numerical examples. The results show that wave propagation in liposomes has a threshold critical frequency beyond which the wave speed drops dramatically and also a cut-off critical frequency below which the corresponding wave mode does not appear. The torsional wave speed is obtained for the symmetrical circumferential mode n = 0. The cut-off or threshold critical frequency decreases with the increase of liposomal radius, but the effect of radius on wave speed is not significant in the frequency region higher than the critical frequency. On the other hand, the wave number n leads to an increase in the critical frequency. For the first and second wave modes, the wave speed is insensitive to the wave number when the frequency is greater than the critical frequency. For the third wave mode in the low frequency region, the wave number leads to an increase in the wave speed. The rotary inertia has little influence on those wave modes which contain cut-off frequencies. For other wave modes, the rotary inertia results in a decrease in the wave speed in the high frequency region. This investigation may provide a useful guide in the applications of liposomes in ultrasound-based drug delivery and release.

AC Characterization of Heated Microcantilevers for Femtogram-Level Thermophysical Property Measurement

2010 ◽  
Author(s):  
Andrew M. Gauffreau ◽  
William DiPippo ◽  
Keunhan Park
Keyword(s):  
Thermal Analysis ◽  
Finite Element Analysis ◽  
High Frequency ◽  
Frequency Region ◽  
Element Analysis ◽  
High Frequency Region ◽  
Doped Silicon ◽  
Before And After ◽  
Property Measurement

This article investigates the electrothermal properties and responses of a doped silicon microcantilever under periodic (ac) Joule heating. To this end, a numerical model using a finite element analysis (FEA) was implemented to compute the steady periodic solutions in the frequency domain. The FEA results agree well with the cantilever ac behavior that was not possible with a previous 1-D analysis. Based on the acquired ac characteristics of the heated cantilever, its feasibility as a probe for nanoscale property measurement was studied by comparing the 3ω voltage signals before and after sampling 449 fg of polyethylene directly on the cantilever. The 3ω signal of the sampled cantilever is considerably different from that of the bare cantilever, suggesting that sample properties can be determined using the processes discussed here. The heater size effect on the ac behavior of the cantilever was also investigated, confirming that the high frequency region is closely related with the thermal diffusion at the heater. The obtained results willexpand the characterization and functionality of microcantilevers leading to advancements in localized thermal analysis.

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