Strong Interference Effects Research Articles

Diagnosis of hydrodynamic regimes from large to micro-fluidized beds

Micro-fluidized bed (MFB) technology is a newly emerging technique that is receiving increasing interest for various industrial applications. MFB is generally characterized by the use of inner diameters (Dt) of a few millimeters, and a large specific contact surface area between the walls and the fluidization system. These specific features have the advantage of enabling ultra-fast heat dissipation for exothermic reactions, as well as isothermal conditions. However, the wall effect also clearly prevails, leading to complicated hydrodynamic phenomena. In addition, the study of MFB is challenging, as a consequence of the difficulties encountered in its characterization, due to strong probe interference effects. In order to understand the wall effect and to make use of suitable fluidization conditions for practical applications of MFB, the present study first establishes a diagnostic methodology, and then applies this to study the influence of a reduction in Dt from large to micro-fluidized bed scales. Experiments were carried out in six glass columns with Dt ranging between 4 and 100 mm, using spherical Geldart group B particles (glass beads). The methodology described here is based on the analysis of pressure fluctuation measurements, which are used to monitor fluidization simultaneously in the time and frequency domains. Fixed bed, pseudo-homogeneous fluidization, bubbling, slugging, and turbulent fluidization regimes are identified in MFBs. When Dt is reduced from large-to micro-fluidized bed scales, minimum fluidization, bubbling and slugging are delayed, whereas the onset of turbulent fluidization occurs more rapidly. The late stage of turbulent fluidization covers a relatively wide range of gas velocities, and is found to have homogeneous fluidization structures, which are of interest for practical MFB applications such as Fischer–Tropsch synthesis.

DOA Estimation for Highly Correlated and Coherent Multipath Signals with Ultralow SNRs

In a typical multipath propagation environment, there exists a strong direct path signal accompanying with several weak multipath signals. Due to the strong direct path interference and other masking effects, the Direction-of-Arrival (DOA) of a weak multipath signal is hard to be estimated. In this paper, a novel method is proposed to estimate the DOA of multipath signals with ultralow signal-to-noise ratio (SNR). The main idea is to increase the SNR and signal-to-interference ratio (SIR) of the desired multipath signal in time-delay domain before DOA estimation processing. Firstly, the cross-correlation functions of the direct path signal and the received array signal are calculated. Then, they are combined and constructed to an enhanced array signal. Under certain conditions, the SNR and SIR of the desired signal can be significantly increased. Finally, the DOAs of multipath signals can be estimated by conventional technologies, and the associated time delays can be measured on the DOA-time-shift map. The SNR and SIR gains of the desired signal are analyzed theoretically, and theoretical analysis also indicates that the Cramer–Rao bound can be reduced. Simulation examples are presented to verify the advantages of the proposed method.

Silicon carbide film-based Fabry-Pérot cavity resonance-enhanced absorption and its application for color filters

We present silicon carbide (SiC)-based Fabry-Perot (F–P) cavities which exhibit highly selective light absorption due to the strong thin film interference effect. Different configurations were discussed here by theoretically exploring the optical response of SiC film on eight metal substrates. Among them, SiC on Al, SiC on Ti and SiC on Pd F–P cavity resonators have the capacity of spectral tunability covering visible light regime, near-perfect absorption and angle dependence resistance. However, SiC on Al substrate architecture, is expected to be the optimal choice in commercial applications, harsh environment and extreme weather. The thickness-dependent properties of SiC-based resonator, in which small thickness variation will result in apparent spectra shift, was also demonstrated. Transfer-Matrix(T-M) method is introduced for calculation. Theoretical results of total round trip phase delay are in very good accordance with the simulations. We believe the SiC-based cavities have a promising application in a variety of research areas such as color filters, photovoltaic devices, no-ink printing and provide an easier way for fabrication.

Universal level statistics of the out-of-time-ordered operator

The out-of-time-ordered correlator has been proposed as an indicator of chaos in quantum systems due to its simple interpretation in the semiclassical limit. In particular, its rate of possible exponential growth at $\hbar \to 0$ is closely related to the classical Lyapunov exponent. Here we explore how this approach to quantum chaos relates to the random-matrix theoretical description. To do so, we introduce and study the level statistics of the logarithm of the out-of-time-ordered operator, $\hat{\Lambda}(t) = \ln \left( - \left[\hat{x}(t),\hat{p}_x(0) \right]^2 \right)/(2t)$, that we dub the "Lyapunovian" or "Lyapunov operator" for brevity. The Lyapunovian's level statistics is calculated explicitly for the quantum stadium billiard. It is shown that in the bulk of the filtered spectrum, this statistics perfectly aligns with the Wigner-Dyson distribution. One of the advantages of looking at the spectral statistics of this operator is that it has a well-defined semiclassical limit where it reduces to the matrix of uncorrelated classical finite-time Lyapunov exponents in a partitioned phase space. We provide a heuristic picture interpolating these two limits using Moyal quantum mechanics. Our results show that the Lyapunov operator may serve as a useful tool to characterize quantum chaos and in particular quantum-to-classical correspondence in chaotic systems, by connecting the semiclassical Lyapunov growth at early times, when the quantum effects are weak, to universal level repulsion that hinges on strong quantum interference effects.

All fibre Q-switched Thulium-doped fibre laser incorporating Thulium–Holmium co-doped fibre as a saturable absorber

A novel all fibre Q-switched Thulium-doped fibre laser (TDFL) is reported which includes a short length of a Thulium–Holmiumco-doped fibre (THDF) as a saturable absorber. A high repetition rate (27.26 kHz) coupled with a low pulse width (19.06μs) is obtained for single wavelength Q-switched pulse operation at an output wavelength of 1911.5 nm using a pump power of 200 mW. Increasing the pump power from 200 mW to 700 mW results in the repetition rate increasing from 27.26 kHz to 99.67 kHz and the pulse width decreasing from 19.06μs to 920 ns. The centre wavelength of the single Q-switched pulse was also red shifted from 1911.5 nm to 1932.5 nm with increasing the pump power. A 45 m length single-mode fibre (SMF-28) provided dispersion compensation, and effectively an SMF-THDF-SMF structure is inserted in the cavity which operates in a similar manner to an SMF-MMF-SMF structure, providing a strong multimode interference effect which supports dual-wavelength operation. A stable dual-wavelength Q-switched pulse was achieved at a threshold pump power of 213 mW. The dual-wavelength Q-switched pulse operation was generated at 1911.5 nm and 1914.5 nm with a repetition rate of 8.45 kHz and pulse width of 20.02μs. The dual-wavelength spacing of this pulse operation was 3 nm, which was in good agreement with calculations based on the multimode interference effect induced by the THDF. The repetition rate increased from 8.45 kHz to 70.65 kHz and the pulse width decreased from 20.02μs to 870 ns with increasing pump power. At the maximum pump power of 700 mW, the maximum output power was measured as 27.4 mW. The experimental results confirm that the THDF can be utilized as a SA to generate a stable and tunable single-wavelength Q-switched pulse output as well as dual-wavelength Q-switched pulse in the 2.0μm wavelength region.

Bismuth-based metamaterials: from narrowband reflective color filter to extremely broadband near perfect absorber

Abstract In recent years, sub-wavelength metamaterials-based light perfect absorbers have been the subject of many studies. The most frequently utilized absorber configuration is based on nanostructured plasmonic metals. However, two main drawbacks were raised for this design architecture. One is the fabrication complexity and large scale incompatibility of these nano units. The other one is the inherent limitation of these common metals which mostly operate in the visible frequency range. Recently, strong interference effects in lithography-free planar multilayer designs have been proposed as a solution for tackling these drawbacks. In this paper, we reveal the extraordinary potential of bismuth (Bi) metal in achieving light perfect absorption in a planar design through a broad wavelength regime. For this aim, we adopted a modeling approach based on the transfer matrix method (TMM) to find the ideal conditions for light perfect absorption. According to the findings of our modeling and numerical simulations, it was demonstrated that the use of Bi in the metal-insulator-metal-insulator (MIMI) configuration can simultaneously provide two distinct functionalities; a narrow near unity reflection response and an ultra-broadband near perfect absorption. The reflection behavior can be employed to realize additive color filters in the visible range, while the ultra-broadband absorption response of the design can fully harvest solar irradiation in the visible and near infrared (NIR) ranges. The findings of this paper demonstrate the extraordinary potential of Bi metal for the design of deep sub-wavelength optical devices.

Charge Transport in Borophene: Role of Intrinsic Line Defects

Very recently, the borophene line defects assembled with υ1/6 and υ1/5 rows were experimentally observed. As the lightest 2D metal sheet, borophene may realize applications in transparent electronic interconnects and electrodes. It is very important and timely to reveal the effects of line defects on quantum transport, which is directly related to borophene-based applications. By using the nonequilibrium Green’s functions and the density-functional theory, here we investigate the charge transport of borophene line defects observed by ultrahigh vacuum scanning tunnelling microscopy in the experiment. It is shown that the presence of υ1/6–υ1/5 boundary weakens the π transmission but almost completely blocks the σ transmission. Furthermore, line defects are found to give rise to quasibound states that strongly hinder propagating electrons in a wide energy region, which is confirmed to originate from strong backscattering and quantum interference effects. This result indicates that borophene with line defects has profound potential for developing novel types of switching devices.

Analysis of Hydrodynamic Performance of L-Type Podded Propulsion with Oblique Flow Angle

In this study, the Reynolds-averaged Navier–Stokes (RANS) method and a model experimental test in a towing tank are used to investigate the unsteady hydrodynamic performance of L-type podded propulsion under different oblique flow angles and advance coefficients. The results show that the load of the operative propeller increases with oblique flow angle and the bracket adds resistance to the pod due to the impact of water flow, leading to a reduced propeller thrust coefficient with increased oblique flow angle. Under a high advance coefficient, the speed of increase of the pressure effect is higher than that of the viscosity effect, and the propeller efficiency increases with the oblique flow angle. The nonuniformity of the inflow results in varying degrees of asymmetry in the horizontal and vertical distributions of the propeller blade pressure. Under high oblique flow angle, relatively strong interference effects are seen between venting vortexes and the cabin after blades, leading to a disorderly venting vortex system after the blade. The numerical simulation results are in good agreement with the experimental values. The study findings provide a foundation for further research on L-type podded propulsors.

Pair production in differently polarized electric fields with frequency chirps

Electron-positron pair production in strong electric fields, i.e., the Sauter-Schwinger effect, is studied using the real-time Dirac-Heisenberg-Wigner formalism. Hereby, the electric field is modeled to be a homogeneous, single-pulse field with subcritical peak field strength. Momentum spectra are calculated for four different polarizations - linear, elliptic, near-circular elliptic or circular - as well as a number of linear frequency chirps. With details depending on the chosen polarization the frequency chirps lead to strong interference effects and thus quite substantial changes in the momentum spectra. The resulting produced pairs' number densities depend non-linearly on the parameter characterizing the polarization and are very sensitive to variations of the chirp parameter. For some of the investigated frequency chirps this can provide an enhancement of the number density by three to four orders of magnitude.

Overall Lifting Technology of Aluminum Plate Unit in the Air Corridor of Raffles City in Chongqing

In this paper, we explore the installation method and process of large-span air corridor curtain wall of Chongqing Raffles Square Project. The curtain wall is positioned at the lower part of the sightseeing overpass, with the spans of 48.5m, 52.6m and 54.1m respectively, and the lengths of the cantilever sections are 25.1m and 26.8m. At the junction of two rivers in Chongqing, several super high-rise buildings nearby exert strong aerodynamic interference effects. It is difficult to construct this project in a conventional way because intense airflow exists. Through an analysis of two construction options, with consideration to difficulties, quality, safety and economic costs of construction by the two options, the overall lifting of aluminum plate unit is chosen as the final plan. An introduction is made to practical operations of this option, including assembly of aluminum plate unit V-frame, tire frame installation, aluminum plate surface layer assembly, hydraulic synchronous lifting and unit body fixing. The hydraulic synchronous lifting process details the technical key points such as lifting point setting, lifting angle control, lifting and windproof measures, hydraulic lifting force control, hydraulic synchronous lifting control, etc. Finally, by utilizing this option, the quality, construction schedule, safety and cost for the overall lifting of units aloft can be guaranteed and good results are achieved in practice.

Characterizing Skeleton Structure and Stacking Properties of Continuous and Gap Graded Aggregate Mixtures

In order to optimize the skeletal properties of granular pavement materials, a numerical discrete element model for continuous and gap graded aggregate mixtures was developed using a step‐by‐step filling method. The penetration tests were conducted, and indexes such as penetrating resistance, average coordination number, California bearing ratio, and void ratio of coarse aggregates obtained from the tests were used to evaluate the skeleton structure and the stacking properties of aggregate mixtures. The results show that the skeleton structure of aggregate mixtures is closely related to the combination of particle size. Smaller difference in particle size leads to stronger interference effect. The parameters of stacking properties of continuous and gap graded aggregate mixtures are not significantly different in the natural stacking condition. However, gap graded aggregate mixtures are affected by external loads significantly due to structural reconstruction.

Modulated Resonant Transmission of Graphene Plasmons Across a λ /50 Plasmonic Waveguide Gap

We theoretically demonstrate the nontrivial transmission properties of a graphene-insulator-metal waveguide segment of deeply subwavelength scale. We show that, at midinfrared frequencies, the graphene-covered segment allows for the resonant transmission through the graphene-plasmon modes as well as the nonresonant transmission through background modes, and that these two pathways can lead to a strong Fano interference effect. The Fano interference enables a strong modulation of the overall optical transmission with a very small change in graphene Fermi level. By engineering the waveguide junction, it is possible that the two transmission pathways perfectly cancel each other out, resulting in a zero transmittance. We theoretically demonstrate the transmission modulation from 0% to 25% at 7.5-µm wavelength by shifting the Fermi level of graphene by a mere 15 meV. In addition, the active region of the device is more than 50 times shorter than the free-space wavelength. Thus, the reported phenomenon is of great advantage to the development of on-chip plasmonic devices.

Study of selective sensing of Hg2+ ions by green synthesized silver nanoparticles suppressing the effect of Fe3+ ions

In this present study, we eliminate the strong interference effect of Fe3+ ions commonly observed in silver nanoparticles (AgNPs) based selective detection of toxic metal ions by localized surface plasmon resonances (LSPRs) of AgNPs. The photoinduced green crystalline silver nanoparticles (NPs) are synthesized using Allium sativum (garlic) extract. The bio ligands act as reducing as well as stabilizing agents and presence of ambient light source enhances the process of nanoparticles formations. The nanoparticles are well characterized by different measurement techniques (UV–vis, DLS-zeta sizer, XRD, TEM). The average particle size as calculated from TEM histogram study was found to be around 10 nm. The as synthesized nanoparticles are employed for selective and sensitive detection of Hg2+ showing excellent sensitivity with a lower detection limit of 2 μM. Fe3+ ions are also capable of oxidizing metallic Ag nanoparticles into ionic Ag+ in water medium and we are able to sense Fe3+ ions are by this green synthesized AgNPs. But the etching of Ag+ ions from AgNPs by Fe3+ ions are extremely quenched by the components of phosphate buffer medium. So the phosphate buffer medium provides good environment around AgNPs for selective and sensitive sensing of Hg2+ ions by lowering the localized surface plasmon resonances.

Achieving nonlinear optical modulation via four-wave mixing in a four-level atomic system

We propose an accessible scheme for implementing tunable nonlinear optical amplification and attenuation via a synergetic mechanism of four-wave mixing (FWM) and optical interference in a four-level ladder-type atomic system. By constructing a cyclic atom-field interaction, we show that two reverse FWM processes can coexist via optical transitions in different branches. In the suitable input-field conditions, strong interference effects between the input fields and the generated FWM fields can be induced and result in large amplification and deep attenuation of the output fields. Moreover, such an optical modulation from enhancement to suppression can be controlled by tuning the relative phase. The quantum system can be served as a switchable optical modulator with potential applications in quantum nonlinear optics.

Spiro-Conjugated Molecular Junctions: Between Jahn-Teller Distortion and Destructive Quantum Interference.

The quest for molecular structures exhibiting strong quantum interference effects in the transport setting has long been on the forefront of chemical research. We establish theoretically that the unusual geometry of spiro-conjugated systems gives rise to complete destructive interference in the resonant-transport regime. This results in a current blockade of the type not present in meta-connected benzene or similar molecular structures. We further show that these systems can undergo a transport-driven Jahn-Teller distortion, which can lift the aforementioned destructive-interference effects. The overall transport characteristics are determined by the interplay between the two phenomena. Spiro-conjugated systems may therefore serve as a novel platform for investigations of quantum interference and vibronic effects in the charge-transport setting. The potential to control quantum interference in these systems can also turn them into attractive components in designing functional molecular circuits.

Colorimetric detection of ultrathin dielectrics on strong interference coatings.

Metal films covered with ultrathin lossy dielectrics can exhibit strong interference effects manifested as the broad absorption of the incident light resulting in distinct surface colors. Despite their simple bilayer structures, such surfaces have only recently been scrutinized and applied mainly to color printing. Here, we report the use of such surfaces for colorimetric detection of ultrathin dielectrics. Upon deposition of a nanometer-thick dielectric on the surface, the absorption peak red shifts, changing the surface color. The color contrast between the bare and dielectric-coated surfaces can be detected by the naked eye. The optical responses of the surfaces are characterized for nanometer-thick SiO2, Al2O3, and bovine serum albumin molecules. The results suggest that strong interference surfaces can be employed as biosensors.

Quantum interference and complex photon statistics in waveguide QED

We obtain photon statistics by using a quantum jump approach tailored to a system in which one or two qubits are coupled to a one-dimensional waveguide. Photons confined in the waveguide have strong interference effects, which are shown to play a vital role in quantum jumps and photon statistics. For a single qubit, for instance, bunching of transmitted photons is heralded by a jump that increases the qubit population. We show that the distribution and correlations of waiting times offer a clearer and more precise characterization of photon bunching and antibunching. Further, the waiting times can be used to characterize complex correlations of photons which are hidden in $g^{(2)}(\tau)$, such as a mixture of bunching and antibunching.

Color printing enabled by phase change materials on paper substrate

We have coated phase change materials (PCMs) on rough and flexible substrates to achieve multicolor changeable devices. The principle of the device is based on an earlier discovery that lights have strong interference effect in PCM films, leading to various colors by reflection. In this work, paper substrates are laminated by parylene layers to protect the device from water before coated with functional PCM films. The PCM-based color printing (PCP) on paper is not affected by rough surfaces and shows a similar color appearance as that on smooth surfaces. In particular, the color-printed device can be patterned by UV lithography to display a clear and tunable optical image, and it exhibits a low sensitivity to the angle of view. Such PCP has potential applications for low-cost, disposable, and flexible displays.

Photorecombination studies of highly charged tungsten ions at Shanghai EBIT

In this paper, we report studies on photorecombination (PR) processes for highly charged W ions. The experiment was performed at Shanghai electron beam ion trap by employing a fast electron beam-energy scanning technique. The KLL dielectronic recombination (DR) resonance strengths for He- up to O-like W ions were determined. The strong interference effect between DR and radiative recombination (RR) was observed and the Fano factor, which measures the interference degree, was determined for the main resonances of ground state He-, Be-, B-, C-, N-, and O-like W ions. In addition, we show experimentally that an autoionizing state can have both Fano and Lorentzian behavior naturally, depending on the processes involved. A fully relativistic configuration interaction method implemented in the flexible atomic code was employed to calculate DR, RR processes and also the inference effect.

음원 간격에 따른 FFR 트랜스듀서 배열의 송신특성 연구

A free flooded ring (FFR) transducer is a ring type projector which has a open backing, cavity, to the water, and it can be applied to a deep sea sound source. A a vertical line array should be constructed to improve the source level but a height of the vertical array should be limited shortly to ensure the sonar operation at sea. In this compact array case, complex interferences caused by cavity modes and mutual radiation impedances may affect on the transmitting responses of the array. Therefore, effects of the element spacing on transmitting characteristics of the FFR transducer array should be understood since the element spacing is the dominant parameter of those interactions. First of all, the transmitting responses of the arrays are numerically calculated according to the element spacing. Strong interference effects related with transmitting characteristics are expected especially around the cavity mode. Simulated results are verified experimentally by underwater acoustic test. Several practical aspects regarding the interference effects are discussed for a sonar design and an operation in this work.