Symmetric Transfer Research Articles

Model order reduction of second-order systems with nonlinear stiffness using Krylov subspace methods and their symmetric transfer functions

ABSTRACTIn this investigation, Model Order Reduction (MOR) of second-order systems having cubic nonlinearity in stiffness is developed for the first time using Krylov subspace methods and the associated symmetric transfer functions. In doing so, new second-order Krylov subspaces will be defined for MOR procedure which avoids the need to transform the second-order system to its state space form and thus the main characteristics of the second-order system such as symmetry and positive definiteness of mass and stiffness matrices will be preserved. To show the efficacy of the presented method, three examples will be considered as practical case studies. The first example is a nonlinear shear-beam building model subjected to a seismic disturbance. The second and third examples are nonlinear longitudinal vibration of a rod and vibration of a cantilever beam resting on a nonlinear elastic foundation, respectively. Simulation results in all cases show good accuracy of the vibrational response of the reduced order models when compared with the original ones while reducing the computational load.

Quantitative differential phase contrast imaging at high resolution with radially asymmetric illumination.

Half-circle illumination-based differential phase contrast (DPC) microscopy has been utilized to recover phase images through a pair of images along multiple axes. Recently, the half-circle based DPC using 12-axis measurements significantly provides a circularly symmetric phase transfer function to improve accuracy for more stable phase recovery. Instead of using half-circle-based DPC, we propose a new scheme of DPC under radially asymmetric illumination to achieve circularly symmetric phase transfer function and enhance the accuracy of phase recovery in a more stable and efficient fashion. We present the design, implementation, and experimental image data demonstrating the ability of our method to obtain quantitative phase images of microspheres, as well as live fibroblast cell samples.

Asymmetric transfer efficiencies between fomites and fingers: Impact on model parameterization

Healthcare-associated infections (HAIs) affect millions of patients every year. Pathogen transmission via fomites and healthcare workers (HCWs) contribute to the persistence of HAIs in hospitals. A critical parameter needed to assess risk of environmental transmission is the pathogen transfer efficiency between fomites and fingers. Recent studies have shown that pathogen transfer is not symmetric. In this study,we evaluated how the commonly used assumption of symmetry in transfer efficiency changes the dynamics of pathogen movement between patients and rooms and the exposures to uncolonized patients. We developed and analyzed a deterministic compartmental model of Acinetobacter baumannii describing the contact-mediated process among HCWs, patients, and the environment. We compared a system using measured asymmetrical transfer efficiency to 2 symmetrical transfer efficiency systems. Symmetric models consistently overestimated contamination levels on fomites and underestimated contamination on patients and HCWs compared to the asymmetrical model. The magnitudes of these miscalculations can exceed 100%. Regardless of the model, relative percent reductions in contamination declined after hand hygiene compliance reached approximately 60% in the large fomite scenario and 70% in the small fomite scenario. This study demonstrates how healthcare facility-specific data can be used for decision-making processes. We show that the incorrect use of transfer efficiency data leads to biased effectiveness estimates for intervention strategies. More accurate exposure models are needed for more informed infection prevention strategies.

Separating fast and slow exchange transfer and magnetization transfer using off‐resonance variable‐delay multiple‐pulse (VDMP) MRI

To develop a method that can separate and quantify the fast (>1 kHz) and slow exchange transfer and magnetization transfer components in Z-spectra. Z-spectra were recorded as a function of mixing time using a train of selective pulses providing variable-delay multipulse build-up curves. Fast and slow transfer components in the Z-spectra were separated and quantified on a voxel-by-voxel basis by fitting the mixing time-dependent CEST signal using a 3-pool model. Phantom studies of glutamate solution, bovine serum albumin solution, and hair conditioner showed the capability of the proposed method to separate fast and slow transfer components. In vivo mouse brain studies showed a strong contrast between white matter and gray matter in the slow-transferring map, corresponding to an asymmetric component of the conventional semisolid magnetization transfer contrast. In addition, a fast-transferring proton map was found that was homogeneous across the brain and attributed to the total contributions of the fast-exchanging protons from proteins, metabolites, and a symmetric magnetization transfer contrast component. This new method provides a simple way to extract fast and slow transfer components from the Z-spectrum, leading to novel MRI contrasts, and providing insight into the different magnetization transfer contrast contributions.

Field patterns without blow up

Field patterns, first proposed by the authors in Milton and Mattei (2017 Proc. R. Soc. A 473 20160819), are a new type of wave propagating along orderly patterns of characteristic lines which arise in specific space-time microstructures whose geometry in one spatial dimension plus time is somehow commensurate with the slope of the characteristic lines. In particular, in Milton and Mattei (2017 Proc. R. Soc. A 473 20160819) the authors propose two examples of space-time geometries in which field patterns occur: they are two-phase microstructures in which rectangular space-time inclusions of one material are embedded in another material. After a sufficiently long interval of time, field patterns have local periodicity both in time and space. This allows one to focus only on solving the problem on the discrete network on which a field pattern lives and to define a suitable transfer matrix that, given the solution at a certain time, provides the solution after one time period. For the aforementioned microstructures, many of the eigenvalues of this -symmetric transfer matrix have unit norm and hence the corresponding eigenvectors correspond to propagating modes. However, there are also modes that blow up exponentially with time coupled with modes that decrease exponentially with time. The question arises as to whether there are space-time microstructures such that the transfer matrix only has eigenvalues on the unit circle, so that there are no growing modes (modes that blow-up)? The answer is found here, where we see that certain space-time checkerboards have the property that all the modes are propagating modes, within a certain range of the material parameters. Interestingly, when there is no blow-up, the waves generated by an instantaneous disturbance at a point look like shocks with a wake of oscillatory waves, whose amplitude, very remarkably, does not tend to zero away from the wave front.

Infrastructure Development Versus Direct Cash Transfer: A General Equilibrium Comparison

Abstract This paper attempts to provide an explanation to the debate whether infrastructure development is more effective than direct cash transfer to reduce wage disparity between skilled and unskilled workers. We use a simple general equilibrium structure to argue that in presence of symmetric productivity effects direct cash transfer meets the target when such transfer is financed by tax revenue collected from skilled wage bill. Nevertheless, in case of asymmetric productivity effects the arguments boil down to how different sectors absorb infrastructural facility to improve their productivity.

Investigation of heat transfer inside a PCM-air heat exchanger: a numerical parametric study

In this paper, the use of PCMs for thermal storage of energy in HVAC applications was investigated by studying numerically the thermal performance of a PCM-air heat exchanger. The PCM used in this study was dodecanoic acid. A symmetric 3D model, incorporating conductive and convective heat transfer (air only) as well as laminar flow, was created in COMSOL Multiphysics 5.0. Simulations examined the dependence of the heat transfer rate on the temperature and velocity of the incoming air as well as the size of the channels in the heat exchanger. Results indicated that small channels size lead to a higher heat transfer rates. A similar trend was also obtained for high incoming air temperature, whereas the heat transfer rate was less sensitive to the incoming air velocity.

Performance analysis and structural optimization of multi-tube type heat integrated distillation column (HIDiC)

Abstract In this research, a multi-tube type heat integrated distillation column was developed and investigated by process simulation. By proper simplification and assumption, the process simulation model of multi-tube type HIDiC was developed in Aspen Plus. Tested by two different binary mixtures, benzene & toluene as well as p-xylene & o-xylene, a detail performance analysis was implemented based on the results of the process simulation. Besides the traditional evaluating parameters such as compression ratio, temperature profile and energy saving, the available energy efficiency and duty drop ratio were first proposed to give a more complete analysis. A systematic economic evaluation was applied to assist the structural optimization process. Moreover, the concept of a symmetric heat transfer HIDiC was proposed to improve operational flexibility and given an advanced research.

Analysis and experimental results of frequency splitting of underwater wireless power transfer

Underwater wireless power transfer (UWPT) is an important technique to power underwater devices while its frequency splitting phenomena are not fully elucidated. In this study, frequency splitting phenomena of a symmetrical planar two-coil wireless power transfer (WPT) system resonated at 90 kHz are investigated in seawater and freshwater. A concise frequency splitting analysis of this WPT system in air based on circuit model is given first and then experimental data are reported to show there is little difference between power transfer in air, freshwater and seawater in the range of 40–140 kHz of this WPT system. Consequently, the frequency splitting analysis and observations in air are also applicable in freshwater and seawater. It is found a V-type frequency splitting pattern exists in this WPT system under seawater and freshwater. Frequency shift is observed in this UWPT system in overcoupled region, and no frequency shift is observed in undercoupled region. In undercoupled region, in the low frequency zone of 40–90 kHz the load voltage characteristics in three media are identical; in the high-frequency zone of 90–140 kHz, the load voltage in air is slightly larger than those in freshwater and seawater.

Correlations for the symmetric converging flow and heat transfer between two nearly parallel stationary disks similar to a solar updraft power plant collector

By focusing on the derivation of the corresponding friction factor and Nusselt number for constant temperature absorber, this work considers the internal symmetric sink flow and heat transfer between two nearly parallel disks stationary similar to the fluid motion in the collector of a Solar Updraft Power Plant. For that, a numerical steady state turbulence model for buoyant incompressible fluids exploiting the variation of the duct cross-section was developed. Friction factor and Nusselt number correlations are suggested for intermediate range of Reynolds numbers, where thermo-hydrodynamic aspects are important for Solar Updraft Power Plant performance assessments.

HYBRID CHRIPTOGRAPHY STREAM CIPHER AND RSA ALGORITHM WITH DIGITAL SIGNATURE AS A KEY

Confidentiality of data is very important in communication. Many cyber crimes that exploit security holes for entry and manipulation. To ensure the security and confidentiality of the data, required a certain technique to encrypt data or information called cryptography. It is one of the components that can not be ignored in building security. And this research aimed to analyze the hybrid cryptography with symmetric key by using a stream cipher algorithm and asymmetric key by using RSA (Rivest Shamir Adleman) algorithm. The advantages of hybrid cryptography is the speed in processing data using a symmetric algorithm and easy transfer of key using asymmetric algorithm. This can increase the speed of transaction processing data. Stream Cipher Algorithm using the image digital signature as a keys, that will be secured by the RSA algorithm. So, the key for encryption and decryption are different. Blum Blum Shub methods used to generate keys for the value p, q on the RSA algorithm. It will be very difficult for a cryptanalyst to break the key. Analysis of hybrid cryptography stream cipher and RSA algorithms with digital signatures as a key, indicates that the size of the encrypted file is equal to the size of the plaintext, not to be larger or smaller so that the time required for encryption and decryption process is relatively fast.

Molecular Outflows in Local ULIRGs: Energetics from Multitransition OH Analysis

Abstract We report on the energetics of molecular outflows in 14 local ultraluminous infrared galaxies (ULIRGs) that show unambiguous outflow signatures (P Cygni profiles or high-velocity absorption wings) in the far-infrared lines of OH measured with the Herschel/PACS spectrometer. All sample galaxies are gas-rich mergers at various stages of the merging process. Detection of both ground-state (at 119 and 79 μm) and one or more radiatively excited (at 65 and 84 μm) lines allows us to model the nuclear gas (≲300 pc) and the more extended components using spherically symmetric radiative transfer models. Reliable models and the corresponding energetics are found in 12 of the 14 sources. The highest molecular outflow velocities are found in buried sources, in which slower but massive expansion of the nuclear gas is also observed. With the exception of a few outliers, the outflows have momentum fluxes of (2–5) × L IR/c and mechanical luminosities of (0.1–0.3)% of L IR. The moderate momentum boosts in these sources (≲3) suggest that the outflows are mostly momentum driven by the combined effects of active galactic nuclei (AGNs) and nuclear starbursts, as a result of radiation pressure, winds, and supernova remnants. In some sources (∼20%), however, powerful (1010.5–11 L ⊙) AGN feedback and (partially) energy-conserving phases are required, with momentum boosts in the range of 3–20. These outflows appear to be stochastic, strong AGN feedback events that occur throughout the merging process. In a few sources, the outflow activity in the innermost regions has subsided in the past ∼1 Myr. While OH traces the molecular outflows at subkiloparsec scales, comparison of the masses traced by OH with those previously inferred from tracers of more extended outflowing gas suggests that most mass is loaded (with loading factors of ) from the central galactic cores (a few × 100 pc), qualitatively consistent with an ongoing inside-out quenching of star formation. Outflow depletion timescales are <108 yr, shorter than the gas consumption timescales by factors of 1.1–15, and are anticorrelated with the AGN luminosity.

Analysis of Low Excitation HDO Transitions toward the High-mass Star-forming Regions G34.26+0.15, W51e1/e2, and W49N

Abstract We present observations of the ground state 10,1–00,0 rotational transition of HDO at 464.925 GHz and the 11,0–10,1 transition at 509.292 GHz, toward three high-mass star-forming regions: G34.26+0.15, W49N, and W51e1/e2, carried out with the Caltech Submillimeter Observatory. For the first time, the latter transition is observed from the ground. The spectra are modeled, together with observations of higher-energy HDO transitions, as well as submillimeter dust continuum fluxes from the literature, using a spherically symmetric radiative transfer model to derive the radial distribution of the HDO abundance in the target sources. The abundance profile is divided into an inner hot core region, with kinetic temperatures higher than 100 K, and a cold outer envelope with lower kinetic temperatures. The derived HDO abundance with respect to H2 is (0.3–3.7) × 10−8 in the hot inner region (T > 100 K) and (7.0–10.0) × 10−11 in the cold outer envelope. We also used two fundamental transitions to constrain the H2O abundances in the outer envelopes. The HDO/H2O ratios in these cold regions are found to be (1.8–3.1) × 10−3 and consequently are higher than in the hot inner regions of these sources.

The square lattice Ising model on the rectangle I: finite systems

The partition function of the square lattice Ising model on the rectangle with open boundary conditions in both directions is calculated exactly for arbitrary system size and temperature. We start with the dimer method of Kasteleyn, McCoy and Wu, construct a highly symmetric block transfer matrix and derive a factorization of the involved determinant, effectively decomposing the free energy of the system into two parts, , where the residual part contains the nontrivial finite-L contributions for fixed M. It is given by the determinant of a matrix and can be mapped onto an effective spin model with M Ising spins and long-range interactions. While becomes exponentially small for large L/M or off-critical temperatures, it leads to important finite-size effects such as the critical Casimir force near criticality. The relations to the Casimir potential and the Casimir force are discussed.

Inflowing gas onto a compact obscured nucleus in Arp 299A

Aims. We probe the physical conditions in the core of Arp 299A and try to put constraints on the nature of its nuclear power source. Methods. We used Herschel Space Observatory far-infrared and submillimeter observations of H2O and OH rotational lines in Arp 299A to create a multi-component model of the galaxy. In doing this, we employed a spherically symmetric radiative transfer code. Results. Nine H2O lines in absorption and eight in emission, as well as four OH doublets in absorption and one in emission, are detected in Arp 299A. No lines of the 18O isotopologues, which have been seen in compact obscured nuclei of other galaxies, are detected. The absorption in the ground state OH 2?3/2-2?3/2(5/2)+-(3/2)-?3/22-2?3/2 52+-32-doublet at 119 ?m is found redshifted by ? 175 km s-1 compared with other OH and H2O lines, suggesting a low excitation inflow. We find that at least two components are required in order to account for the excited molecular line spectrum. The inner component has a radius of 20-25 pc, a very high infrared surface brightness (3 × 1013L·kpc-2), warm dust (Td > 90 K), and a large H2 column density (NH2 > 1024 cm-2). The modeling also indicates high nuclear H2O (1-5 × 10-6) and OH (0.5-5 × 10-5) abundances relative to H nuclei. The outer component is larger (50-100 pc) with slightly cooler dust (70-90 K) and molecular abundances that are approximately one order of magnitude lower. In addition to the two components that account for the excited OH and H2O lines, we require a much more extended inflowing component to account for the OH 2?3/2-2?3/2(5/2)+-(3/2)- ?3/22-2?3/2 52+-32-doublet at 119 ?m. Conclusions. The Compton-thick nature of the core makes it difficult to determine the nature of the buried power source, but the high surface brightness indicates that it is an active galactic nucleus and/or a dense nuclear starburst. Our results are consistent with a composite source. The high OH/H2O ratio in the nucleus indicates that ion-neutral chemistry induced by X-rays or cosmic-rays is important. Finally we find a lower limit to the 16O/18O ratio of 400 in the nuclear region, possibly indicating that the nuclear starburst is in an early evolutionary stage, or that it is fed through a molecular inflow of, at most, solar metallicity.

Gigahertz frequency doubler based on millimeter-scale single-crystal graphene

Graphene shows great potential applications in ultrahigh speed electronics due to its high carrier mobility and velocity. Nowadays, many radio frequency circuits based on graphene have been realized. For example, graphene frequency doubler is a promising option for signal generation at high frequencies. Graphene frequency doubler can achieve excellent spectral purity, because of its ambipolar transport and highly symmetric transfer characteristics. Here, we present high performance graphene frequency doublers based on millimeter-scale single-crystal graphene on HfO2 and Si substrates. We achieve a high spectral purity degree of larger than 94% without any filtering and the conversion gain is -23.4 dB at fin=1 GHz. The high conversion gain and spectral purity can be attributed to the high-quality millimeter-scale single-crystal graphene and high-quality high- substrates. Furthermore, we investigate the relation of conversion gain to source-drain voltage Vd and input signal power Pin. The results show that the conversion gain increases with source-drain voltage increasing, and the conversion gain also increases with input signal power increasing. The dependence of conversion gain on Vd and Pin can be attributed to the transconductance increasing with Vd and Pin. We compare the conversion gains and spectral purity degrees of graphene frequency doublers with different transconductances and electron-hole symmetries at different frequencies. The result shows that the conversion gain is larger for device with higher transconductance and the spectral purity has a moderate tolerance for the electron-hole symmetry of the graphene transistor at fin=1 GHz. As the working frequency increases to 4 GHz, the spectral purity of the device with weak electron-hole symmetry decreases dramatically, while the spectral purity of the device with better electron-hole symmetry is kept around 85%. We attribute this phenomenon to the different carrier transit times and different electron-hole symmetries of graphene transistors. In conclusion, the short channel graphene transistor with ultrathin gate dielectric and high electron-hole symmetry is needed in order to achieve high performance graphene frequency doubler.

Property of Rational Functions Related to Band-Pass Transformation With Application to Symmetric Filters Design

This paper considers the condition when a rational function $F(s)$ may be represented as the function of the argument $s+(1/s)$ . If this condition is satisfied then $F(s)$ is the ratio of recursive (symmetric) polynomials. This paper investigates the network properties of such rational functions and their realization. Then the symmetric polynomials are applied for synthesis of symmetric band-pass filters. Substituting $p=s+(1/s)$ into symmetric band-pass filter transfer function one obtains its low-pass generating filter. The slew rate and overshoot of generating filter step-response is closely connected with the step-response duration of symmetric band-pass filter. The choice of generating filter becomes an additional factor of symmetric band-pass filter design. As the generating filters the paper proposes using Lommel polynomial filters which have easy control of overshoot and slew rate. An example of six order symmetric band-pass filter is given.

Blind image quality assessment based on wavelet power spectrum in perceptual domain

Blind image quality assessment (BIQA) can assess the perceptual quality of a distorted image without a prior knowledge of its reference image or distortion type. In this paper, a novel BIQA model is developed in wavelet domain. Considering the multi-resolution and band-passing characteristics of discrete wavelet transform (DWT), an improvement over the power spectrum is put forward, i.e., dubbed wavelet power spectrum (WPS) estimation. Then, the concept of directional WPS is applied to simplify the calculation. Moreover, a rotationally symmetric modulation transfer function (MTF) of human visual system (HVS) is integrated as a filter, which makes the metric to be consistent with the human vision perception and more discriminative. Experiments are conducted on the LIVE databases and three other databases, and the results show that the proposed metric is highly correlated with subjective evaluations and it competes well with other state-of-the-art metrics in terms of effectiveness and robustness.

Analysis of electrostatic doped Schottky barrier carbon nanotube FET for low power applications

This paper presents the analysis of electrostatic doped Schottky barrier carbon nanotube FET (ED-SBCNTFET) for low power applications. Electrostatic doping is introduced in intrinsic CNT as a channel material which reduces the process complexity; moreover dynamic configuration provides symmetric transfer characteristics for n-type and p-type for ED-SBCNTFET. Simulation results demonstrate that ED-SBCNTFET is better than conventional CNTFET in terms of IOFF and subthreshold swing (SS) which makes it suitable for low power applications. Simulations are performed and sensitivity analysis is carried out for CNT diameter, effective oxide thickness (EOT), high-k dielectric and polarity gate bias. It is observed that CNTs are most sensitive to diameter, since CNT with diameter 0.85 nm exhibits ION/IOFF ratio of ~109 and SS of 60.8 mv/dec whereas diameter of 0.55 nm results into ION/IOFF ratio of ~1011 with SS of 58.5 mv/dec. Optimized parameters are proposed for low power applications in terms of IOFF and SS. ED-SBCNTFET has been analysed for various process parameters and it has been demonstrated to be less sensitive to process variations.

Numerical study of a PCM-air heat exchanger's thermal performance

In this paper, the use of PCMs in HVAC applications is investigated by studying numerically the thermal performance of a PCM-air heat exchanger. The PCM used in this study is dodecanoic acid. A symmetric 3D model, incorporating conductive and convective heat transfer (air only) as well as laminar flow, was created in COMSOL Multiphysics 5.0. Simulations examined the dependence of the heat transfer rate on the temperature and velocity of the incoming air as well as the size of the channels in the heat exchanger. Results indicated that small channels size lead to a higher heat transfer rates. A similar trend was also obtained for high incoming air temperature, whereas the heat transfer rate was less sensitive to the incoming air velocity.