Order Modes Research Articles

Proper orthogonal decomposition and physical field reconstruction with artificial neural networks (ANN) for supercritical flow problems

The development of mathematical models, and the associated numerical simulations, are challenging in higher-dimensional systems featuring flows of supercritical fluids in various applications. In this paper, a data-driven methodology is presented to achieve system order reduction, and to identify important physical information within the principal flow features. Firstly, a new hybrid neural network based on radial basis function (RBF) and multi-layer perceptron (MLP) methods, namely RBF-MLP, is tested to achieve a highly nonlinear approximation. When provided with 1000 nonlinear test samples, this model provides an excellent prediction accuracy with a maximum regression coefficient (R) of 0.99 and a minimum root mean square error (RMSE) below 1%. Furthermore, the model is also proven to be flexible enough to capture accurately the turbulent fluctuation characteristics, even at significant nonlinear buoyancy conditions. Secondly, the high-dimensional buoyancy data is collected and integrated into a matrix database. Subsequently, a proper orthogonal decomposition (POD) approach is employed to reduce the high-dimensional database, and to obtain a set of low-dimensional POD basis-spanned space, which defines a reduced-order system with low-dimensional basis vectors. The results reveal that the first five order modes contain dominant flow features, accounting for 93% of the total mode energy, which can be selected to reconstruct the physical flow field. Thirdly, a new data-driven POD-ANN model is established to construct the nonlinear mapping between the full-field buoyancy data and decomposed basis vectors. It is also demonstrated that the POD-ANN model reconstructs the principal flow features accurately and reliably. This POD-ANN model can be used to provide new insights for reduced-order modelling and for reconstructing physical fields of higher-dimensional nonlinear flow cases.

Coherence and reduced order analyses of flow field and aerodynamic noise for full-scale high-speed trains pantograph

Unsteady flow field and far-field noise generated by full-scale high-speed trains pantograph were predicted by large eddy simulation and FW-H equation, and analyzed by coherence and reduced-order analyses. The agreement between simulation and test of tandem square cylinder at close Reynolds number of 1.8 × 105 indirectly validates the numerical method of full-scale pantograph. For the full-scale pantograph running at the speed of 300 km/h, the total sound pressure level radiated to the standard far-field receiver is 81.2 dB. The far-field noise radiated by the pan-head is more significant than that of the support rod and base frame, and the peak noise occurs at the frequencies of 252 Hz and 353 Hz. The coherence analysis shows that the peak noise frequency of 252 Hz generates near the knuckle of the pan-head and the upper arm, and that of 353 Hz generates in the middle position of the pan-head’s three rods, where there is a complete vortex shedding structure with positive and negative phase distribution. The reduced-order analysis shows that the first and second order modes containing the most energy represent the spatial vortex shedding around the pan-head. A typical wake flow with the frequency of 353 Hz is shed behind the pantograph rods, while an alternating vortex with the frequency of 252 Hz is shed on both sides of the rods.

Two-photon microscopy with enhanced resolution and signal-to-background ratio using hollow Gaussian beam excitation.

Two-photon microscopy (TPM) offers deeper imaging depth inside the scattering medium, however, it suffers from limited resolution owing to the longer excitation wavelength. We demonstrate the use of a hollow Gaussian beam (HGB) at the therapeutic window to improve the resolution and signal-to-background ratio (SBR). The HGB was produced by omitting the azimuthal phase term from the vortex mode, and the excitation point spread function (PSF) can be readily tuned by the mode order. The performance of the TPM with HGB was evaluated by experimentally imaging 100 nm fluorescent beads to estimate the PSF. The HGB improved the lateral resolution of the TPM by 36% in contrast to the conventional TPM. The HGB also furnishes an improvement of SBR by eliminating the out-of-focus light owing to its ring shape. Furthermore, we have used a translating lens-based module for additional lateral resolution tuning and reduced the resolution further down to 44% with respect to conventional TPM. Finally, we have performed imaging with merely two-dimensional scanning of a 50 µm thick mouse brain slice (Thy-YFP H-line) using the developed TPM with HGB. Our compact, robust, and low-cost design of the HGB generation scheme can easily be integrated into the commercial TPM to accommodate the improvements.

Characterization of Spray Modes and Factors Affecting the Ionization Efficiency of Paper Spray Ionization.

In this study, we systematically evaluated the factors affecting the ionization efficiency of paper spray ionization (PSI), such as electric field, solvent supply rate, and paper thickness and hydrophobicity. The observed paper spray plume was classified into three modes: single cone-jet, multi-jet, and rim-jet modes. With the increase in the spraying voltage, the spray plume appeared in order of single cone-jet, multi-jet, and rim-jet modes. The rim-jet mode exhibited the lowest standard deviation and high ionization efficiency among the three spray modes. The main parameter determining the spray mode was the charge density of the droplets generated by paper spray, which depends on the electric field and solvent supply rate. A thicker paper reduced the electric repulsion between the jets and lowered the threshold voltage to reach the rim-jet mode. Lowering the solvent supply rate caused mode transitions from the single cone-jet to the rim-jet, possibly due to the increased droplet charge density. The hydrophobic modification on a paper substrate led to a different ionization mechanism or electrostatic spray ionization at low applied voltages.

Two-body hadronic decay of K+ in the presence of a circularly polarized laser field

In this study, we have investigated the two-body hadronic decay of the charged kaon, , in the presence of a laser field with circular polarization. We have derived, by analytical techniques, the laser-assisted decay width and the branching ratio of the charged kaon decay via the two-body hadronic channel. We have also taken into consideration the impressive results obtained for the laser-assisted charged kaon decay via the leptonic mode in order to understand more clearly the effect of the laser field on the quantities related to the charged kaon decay such as the decay width, the branching ratio and lifetime. A precise comparison of the ratios of hadronic-to-muonic decay in the presence of the laser field is made to show that the hadronic mode becomes slightly more important by increasing the laser field intensity.

The Blue House: An analysis of the production of Johar Up in the Air!

This article provides an analysis of a drama therapy process carried out during 2012‐17 with a group of imprisoned persons labelled by the Lebanese Penal Code as ‘insane, mad, or possessed’, some of whom were housed in the notorious Blue Building in Roumieh Prison in Beirut, Lebanon. The author argues for the use of a hybrid approach to drama therapy inside prisons that simultaneously includes forms of self-advocacy, legislative theatre and self-revelatory modes in order to successfully hold up a mirror to Lebanese society, implicating its anachronistic legal codes in the oppression that often leads to chaos and madness. In the course of collaborating on their artistic journey, two segregated populations of participants, one identified by the Lebanese Penal Code as ‘insane’ and the other as ‘regular’, collaborated and revealed stories of domestic violence, traumatic childhoods, social dysfunctions, the lingering impact of an earlier civil war and the deprivation of legal and human rights. Standing up before numerous audiences, including high officials of the government, they dared not only to reflect on their own lives but also to heal their own and their community’s wounds.

Selective Detection of Liquid Viscosity Using Acoustic Plate Waves with In-Plane Polarization.

Using plates of weak piezoeletcric crystal (quartz) loaded with various liquids, it is shown that along with common modes, whose sensitivity towards different liquid parameters comparable with each other, there are some uncommon modes, whose amplitude responses towards viscosity η are much larger than towards temperature T and electric conductivity σ. The search of the modes with the selective properties is accomplished by varying plate thickness h, crystal orientation, wave length λ, and mode order n. It is found that all modes possessing the property are characterized by small surface-normal displacement, avoiding wave radiation into adjacent liquid, large in-plane displacements, enhancing viscous coupling the modes and liquids, and small electro-mechanical constant, reducing electro-acoustic interaction. Basing on the modes, the sensor prototypes with selective operation are developed and tested for η from 1 to 1500 cP, σ from 0 to 1.2 S/m, and t from 0 to 55 °C. Because of operation at ultrasonic frequency (tens MHz) the prototypes have different sensitivities in various η-ranges: 0.3 dB/cP for 1–20 cP, 0.12 dB/cP for 20–100 cP, and 0.015 dB/cP for 100–1500 cP. Viscosity responses of the prototypes become comparable with their electric outputs only for η < 2 cP. Temperature responses are almost zero in air, but when plate is coated with liquid they increase depending on liquid properties, allowing measurements of the temperature dependence of the liquid viscosity.

Perfect Control of Diffraction Patterns with Phase-Gradient Metasurfaces.

Phase-gradient metasurfaces (PGMs) constitute an efficient platform for deflection of a beam in a desired direction. According to the generalized Snell's law, the direction of the reflected/refracted wave can be tuned by the spatial phase function provided by the PGMs. However, most studies on PGM focus only on a single diffraction order, that is, the incident wave can be reflected or refracted to a single target direction. Even in the case of multiple beams pointing in different directions, the beams are still in the same order mode, and the energy carried by different beams cannot be controlled. In addition, the energy ratio of multiple beams is generally uncontrollable. Here, we propose a general method to perfectly control diffraction patterns based on a multi-beam PGM. An analytical solution for arbitrarily controlling diffraction beams is derived through which the generation and energy distribution in high-order diffraction beams can be achieved. Three metasurfaces with different diffraction orders and energy ratios are designed and fabricated to demonstrate the proposed method. The efficiencies of diffraction for the desired channels are close to 100%. The simulated and measured far-field patterns are in good agreement with theoretical predictions, validating the proposed method that provides a new way to design multi-beam antennas and that has significance in wireless communication applications.

High-energy Q-switched 16-core tapered rod-type fiber laser system.

High-energy Q-switched master oscillator power amplifier systems based on rod-type 4 × 4 multicore fibers are demonstrated, achieving energy up to 49 mJ in ns-class pulses. A tapered fiber geometry is tested that maintains low mode order in large multimode output cores, improving beam quality in comparison to a similar fiber with no taper. The tapered fiber design can be scaled both in the number of amplifying cores and in the dimensions of the cores themselves, providing a potential route toward joule-class fiber lasers systems.

Research on the Application of Data Mining Technology in College Students’ Mental Health Education in the Network Age

As the marcher of life in the times, the network has penetrated into all fields of life and played an immeasurable role. As a specific contemporary group, college students have a weak sense of self-protection and are very vulnerable to adverse factors. Some colleges and universities are trying to explore various psychological intervention modes in order to conduct psychological counselling and prediction more objectively. Network mental education means that, on the premise of using social networks, educators use psychological science methods to exert a positive impact on all aspects of students' mental health education, so as to promote the development of contemporary mental health of college students under social networks and cultivate the correct mentality of using social networks. It is combined with the established college students' rational correlation analysis system. Based on the collected data and basic information of college students' rational evaluation, the improved mining algorithm is used, and some rules and characteristics of college students' psychological related factors are analyzed from the results, which provides a new idea for college students' rational health education. Aiming at realizing the embedded data mining technology in the psychological management system, this paper expounds in detail the design and implementation of the data mining technology module suitable for the psychological management system and discusses the factors affecting students' mental health.

Experimental study on flexural behavior of GFRP reinforced concrete beams

Glass fiber reinforced polymer (GFRP) has been investigated and popularly used as internal reinforcement in the construction field worldwide. Although GFRP is not easy to be corroded, employing it requires an avoidance of the brittle failure mode in order to replace traditional reinforced concrete in designing flexural elements. Therefore, this study brings an incisive view to flexural behavior of concrete beams with GFRP as reinforcements in contribution to apply GFRP to coastal and island construction in Vietnam. This study is based on the tested beams under 3-point bending test and theoretical analysis. The moment resistance of GFRP reinforced concrete beams was designed according to ACI 440-1R code. Materials including GFRP bars and concrete to fabricate tested beams were produced in Vietnam. The investigation reached a conclusion that GFRP is eligible for manufacturing flexural components, which is a potential alternative for traditional concrete in the construction industry.

Tunable terahertz Bessel beams with orbital angular momentum

In this work we demonstrate a frequency-tunable terahertz (THz) Bessel beam with zero- and first- order modes and orbital angular momentum, by utilizing a Tsurupica Axicon lens in combination with a picosecond difference frequency generation laser. This system enabled the selective generation of zero- or first-order THz Bessel beams with frequency-tunability across the range 3–7 THz.

Multiple Periodic Vibrations of Auxetic Honeycomb Sandwich Plate with 1:2 Internal Resonance

In this paper, we focus on the multiple periodic vibration behaviors of an auxetic honeycomb sandwich plate subjected to in-plane and transverse excitations. Nonlinear equation of motion for the plate is derived based on the third-order shear deformation theory and von Kármán type nonlinear geometric assumptions. The Melnikov method is extended to detect the bifurcation and multiple periodic vibrations of the plate under 1:2 internal resonance. The effects of transverse excitation on nonlinear vibration behaviors are discussed in detail. Evolution laws and waveforms of multiple periodic vibrations are obtained to analyze the energy transfer process between the first two order modes. Even quite small transverse excitation can cause periodic vibration in the system, and there can be at most three periodic orbits in certain bifurcation regions. The periodic orbits are classified into two families by tracing their sources. The study provides the possibility for the classification study on generation mechanism of system complexity and energy transfers between different modes.

Frequency control strategies in a renewable energy intensive power system: options for South Africa

Inertia reduction due to high-level penetration of converter interfaced components may result in frequency stability issues. The paper analyses different frequency strategies for both solar photovoltaic (PV) and wind generators to support inertia, and also evaluates the contribution of synchronous condensers (SCs) to the system inertia of the power grid. Decommissioned power plants can potentially be retrofitted to SC mode in order to provide inertia support after they are retired. This paper investigates the various frequency control strategies available to the South Africa power grid in the face of increasing renewable energy integration, and makes a case for the modification of the many mothballed coal-fired power plants to SC mode.

Emissions assessment of bulk carriers in China's east Coast-Yangtze River maritime network based on different shipping modes

In the past decades, resources such as iron ore were transported to the upper-middle reaches of the Yangtze River by river-sea combined mode in order to support the rapid economic development of Yangtze River Economic Zone. However, emissions from vessels have caused serious negative effect on the environment along the Yangtze River. Therefore, the Chinese government took a series of measures so as to control the emissions in this area. This paper draws comparisons among river-sea combined mode, river-sea mode and mixed mode (combination of the river-sea combined mode and river-sea mode) based on the ship emissions inventory of SOx, PM10, PM2.5, NOx, CO, HC, CO2, N2O and CH4 for 13 common cases in the existing network by bottom-up method. In addition, the paper carries out in-depth analyses, providing evidence for future ship operation directions. The results indicate river-sea mode and mixed mode which implement river-sea vessels record less unit emissions compared to the traditional river-sea combined mode. Moreover, shorter transshipment (lightning) times, proper ports of transshipping and cleaner fuels are able to reduce ship emissions significantly. Hence, we conclude that first, river-sea vessels should be encouraged; second, the initiative of a deep-water channel of the Yangtze River should be continued; and last, stricter regulations of fuels have played a significant role in reducing ship emissions.

Observation of Squeezed States of Light in Higher-Order Hermite-Gaussian Modes with a Quantum Noise Reduction of up to 10dB.

Mirror thermal noise will be a main limitation for the sensitivities of the next-generation ground-based gravitational-wave detectors (Einstein Telescope and Cosmic Explorer) at signal frequencies around 100Hz. Using a higher-order spatial laser mode instead of the fundamental mode is one proposed method to further mitigate mirror thermal noise. In the current detectors, quantum noise is successfully reduced by the injection of squeezed vacuum states. The operation in a higher-order mode would then require the efficient generation of squeezed vacuum states in this mode to maintain a high quantum noise reduction. In our setup, we generate continuous-wave squeezed states at a wavelength of 1064nm in the fundamental and three higher-order Hermite-Gaussian modes up to a mode order of 6 using a type-I optical parametric amplifier. We present a significant milestone with a quantum noise reduction of up to 10dB at a measurement frequency of 4MHz in the higher-order modes and pave the way for their usage in future gravitational-wave detectors as well as in other quantum noise limited experiments.

Investigation on Mode Characteristics of Rotating Instability and Rotating Stall in an Axial Compressor

Abstract Rotating instability (RI) and rotating stall (RS) are two types of aerodynamic instability in axial compressors. The former features the side-by-side peaks below the blade passing frequency (BPF) in frequency spectra, and the latter represents one or more stall cells rotating in the compressor. This article presents an experiment on the nearfield pressure and farfield acoustic characteristics of RI phenomenon in a low-pressure axial compressor rotor, which endures both RI and RS at several working conditions. To obtain the high-order modes of RI and other aerodynamic instability, a total of 9 or 20 Kulites are circumferentially mounted on the casing wall to measure the nearfield pressure fluctuation using a mode order calibration method. Meantime in the farfield 16 microphones are planted to measure the acoustic mode order using the compressive sensing method. Through calibration, the experiments acquire the mode orders generated by RI and the interaction between RI and BPF, which are higher than the number of transducers. As for RS, the mode decomposition shows a mode order of 1, indicating one single stall cell rotating in the compressor. This experiment also shows that the amplitudes of RI modes are decreased when RS occurs, but both RS modes and RI modes will be enhanced if the flowrate is further reduced. This experiment reveals that RI experiences three stages of “strengthen-weaken-strengthen,” and hence, RI may not be regarded only as “prestall” disturbance.

Structural Optimization of Vented Brake Rotors with a Fully Parameterized Model

Vented brake rotors used in an automobile behave similarly to centrifugal fans, drawing cool air from the inboard side, passing it through the disc vents, and exhausting it from the periphery. A vented brake rotor with a better heat dispersing ability is often superior to a solid rotor, in both thermal performance and brake efficiency. In this research, a fully parameterized model for a ventilated brake rotor is created using the ANSYS Parametric Design Language, to uniquely define the rotor’s geometry. With this parameterized model, two structural optimization cases are studied in this paper. The first one investigated is a modal frequency separation problem: The frequency differences in a tangential mode sandwiched between two nodal diameter modes of the brake rotor model are maximized. An automatic identification scheme for extracting correct mode orders is implemented in the program to track the correct modes during optimization. The second case is a thermal deformation problem: The distortion on the frictional surfaces of the rotor loaded with heat flux generated during the braking process is minimized. The optimization results show that a brake rotor design with a thinner outboard disc and a thicker inboard disc provides a great choice for rotor coning reduction.

Effects of Game Mode in Multiplayer Video Games on Intergenerational Social Interaction: Randomized Field Study.

BackgroundMaintaining social relationships is a basic human need and particularly essential in old age, including when living in a retirement home. Multiplayer video games can promote positive social interactions among players from different generations while playing. Yet, such facilitation of positive social interactions depends on specific game design. To systematically investigate the effects of game design on social interaction between seniors and their coplayers, the game Myosotis FoodPlanet was developed in this study, and the impacts of 3 different game modes on social interaction were compared in a controlled field trial.ObjectiveThis study aims to compare the effects of 3 different game modes (competitive, cooperative, and creative) on social interactions (verbal and nonverbal communication) between seniors and their younger coplayers.MethodsThis study was conducted in a Swiss retirement home as a controlled field trial. Participants were residents of the retirement home (N=10; mean age 84.8 years, SD 5.9 years) and played in pairs with their caregivers. Each pair played 3 game modes in random order. This resulted in 30 game sequences of 20 minutes each. A within-subject design was applied with game mode as the within-factor and social interaction as the outcome variable. To assess the quality of social interaction, 30 video-recorded game sequences were analyzed based on an event sampling method.ResultsAnalysis of variance for repeated measurements revealed significant effects: there was significantly more verbal communication in the creative mode than in the cooperative mode (P=.04) with a strong effect size (Cohen f=0.611). An examination of verbal communication revealed more game-related communication in the creative mode than in the cooperative mode (P=.01) and the competitive mode (P=.09) with marginally significant effects and strong effect sizes (Cohen f=0.841). In addition, significantly more biography-related communication occurred in the creative mode than in the cooperative mode (P=.03), with a strong effect size (r=0.707). Regarding nonverbal communication (eg, laughing together), analysis of variance for repeated measurements showed significant differences among the game modes (P=.02) with a strong effect size (Cohen f=0.758). Results showed that there was significantly more laughing together in the competitive mode (competitive>cooperative>creative).ConclusionsThe results show that game mode can be an important factor for shaping the social interactions of players playing together. Compared with other modes, creative game modes can increase verbal communication. In contrast, competitive modes may stimulate more laughing together. This has important implications for game design and the use of computer games to promote social interaction between seniors and their coplayers in practice.

Quality Assurance for the Appearance of Paint Coatings

The article provides information on the application of statistical methods of product quality management to the analysis of the process of obtaining paint and varnish coatings with desired properties. A correlation has been established between the standard deviations of the roughness indicators of the coating surface and the surface to be painted. The relationship between the standard deviations for the surface roughness of the coatings and the surface to be painted is given. The results of calculating the values of the root-mean-square deviation of the roughness of the coatings and the class of roughness of the substrate surface, providing with a probability of 0.95 a given class of roughness of the coating surface. The calculation results make it possible to choose a more optimal staining mode in order to obtain a smaller spread in the roughness index of the formed coating. This provides a guaranteed level of quality for the painted surface.