Pump Field Research Articles

Effect of phase fluctuations on atomic Talbot images in three-level ladder-type atomic system

In this article, we study the atomic Talbot effect in a three-level ladder-type atomic system, which consists of a strong microwave field having a finite bandwidth and a weak probe field. The upper levels are coupled with a strong position-dependent microwave field, while a weak probe field interacts with lower levels of the atomic system. We find that phase fluctuations associated with a strong microwave field significantly affect the transmission and corresponding intensity of Talbot images. We show that the choice of various parameters is crucial in the presence of phase fluctuation. An appropriate choice along with a pump field can still improve the intensity of atomic Talbot images. We believe that our results are useful for any practical situation where the effects of phase fluctuations are important.

ẢNH HƯỞNG CỦA ĐỘ KẾT HỢP ĐƯỢC TẠO BỞI PHÁT XẠ TỰ PHÁT VÀ BƠM KHÔNG KẾT HỢP LÊN CHUYỂN MẠCH TOÀN QUANG TRONG MÔI TRƯỜNG NGUYÊN TỬ BA MỨC BẬC THANG KHI CÓ MẶT CỦA PHA TƯƠNG ĐỐI

This paper investigates the impact of spontaneously generated coherence (SGC) and relative phase on the propagation of a probe laser pulse in the presence of an incoherent pump field. It was discovered that when the control laser field is turned on, the medium forms an electromagnetically induced transparency (EIT) effect. Hence, the propagation of the probe laser pulse has a like-soliton form/shape. On the contrary, the probe laser field is rapidly attenuated when the control laser field is turned off. This feature allows the creation of a mechanism to turn “off” and “on” the probe laser field through “turning off” and “on” the control laser field, i.e., an all-optical switching mechanism based on EIT. Besides intensity and frequency, the laser field is also characterized by polarization and phase. The EIT has the nature of quantum interference, so it is very sensitive to changes in polarization, especially in the presence of relative phase between laser fields. Therefore, they also significantly affect pulse propagation and optical switching performance. The research results could be helpful for experimental observations or applications in photonic devices such as logic gates, quantum optical information processors, and quantum computers.

Study on the influence of non-newtonian fluid characteristics on the hydraulic performance and internal flow field of multiphase pump

As a pivotal prospective clean energy source, the secure and efficient extraction of natural gas hydrate has emerged as a forefront concern within the global oil drilling industry in recent years. In this study, a self-developed multiphase pump adapted to "gas-liquid-solid" three-phase mixing is used to extract natural gas hydrate slurries which have non-Newtonian characteristics. Prior research on pumps has primarily focused on water, introducing a significant disparity in handling slurries containing hydrates. This paper investigates the hydraulic performance and flow field variations of a multiphase pump using three different concentrations of Herschel-Bulkley non-Newtonian fluids that exhibit rheological properties similar to natural gas hydrate slurries. Additionally, a viscous Newtonian fluid with seawater as the liquid phase medium is studied for comparison. The results show that the shear-thinning properties of the non-Newtonian fluid improve the efficiency of the pump. However, excessive concentration negatively affects the hydraulic properties. The flow field characteristics such as apparent viscosity and turbulent kinetic energy are closely related to the pump structure and fluid properties. Compared with viscous Newtonian fluid, the non-Newtonian fluid's also have a greater effect on the distribution of gas-solid phases.

INFLUENCE OF GENERATED PUMP ELECTRIC FIELD ON MULTIHARMONIC INTERACTION OF WAVES IN AMPLIFICATION SECTION OF SUPERHETERODYNE FEL

In the cubic nonlinear approximation, we analyze the processes of generating the electric pump field by an electron beam and its effect on the amplification of space charge waves (SCW) in the amplification section of a parametric superheterodyne free-electron laser (FEL). We found that the generated pump electric field amplitude is within 21…33% of the amplitude of the external pump electric field. We showed that the generated pump electric field is in phase with the external one. It leads to an increase in the growth increments of SCW; therefore, the length of the SCW amplification section is reduced by 22%. We found out that this field does not destroy the mode of amplification of multi-harmonic SCW. Thus, the studied effect makes it possible to create FELs with smaller longitudinal dimensions and powerful electromagnetic waves with a complex multi-harmonic spectrum.

Room temperature persisting surface charge carriers driven by intense terahertz electric fields in a topological insulator Bi2Se3

Topologically protected surface current is highly promising for next-generation low-dissipation and disorder-tolerant quantum electronics and computing. Yet, electric transport from the co-existing bulk state dominates the responses of the Dirac surface state, especially at elevated temperatures relevant to technological applications. Here, we present an approach that convincingly showcases the generation, disentanglement, and precise control of enduring surface charge carriers on a topological insulator, Bi2Se3, with high bulk conductivity, all achieved at room temperature. By using pump–probe modulation spectroscopy under ultrabroadband driving tunable from 4 meV to 1.55 eV, we show the terahertz (THz) field-induced surface carriers by discovering their initial temporal responses dominant over high density trivial bulk carriers. Strikingly, the response of the induced surface carrier responses persists for more than ∼5 ps and is enhanced by reducing pump photon energy. The dynamics and lifetime of the distinct surface response manifest themselves as the enhanced THz pump-induced THz transmission, which directly correlates with the transient negative THz conductivity. Increasing the THz driving field reduces the induced surface carrier lifetime and identifies, particularly, an optimal pump field of Es ∼ 224 kV cm−1 for generating the dominant surface response relative to the bulk. This surface carrier dominant regime is suppressed by a joint effect of enhanced surface-bulk scattering and a more rapid saturation of surface excitation compared to the bulk that sets in above Es. The controllability of room temperature topologically surface carriers through pump photon energy offer compelling possibilities for extending this approach to other topological complex materials.

Модель информационно-измерительной системы контроля центробежного грузового насоса на танкере-химовозе типа «Иван Поддубный»

On chemical tankers, the main cargo devices are pumps, so it is necessary to constantly monitor their operating conditions and performance indicators during operation. The article discusses modeling using MATLAB/Simulink software of a single-stage horizontal centrifugal pump, which can be used to create an information-measuring system for monitoring the performance of cargo pumps using the example of a chemical tanker of the Ivan Poddubny type. An analysis of the modeling results is carried out, including an assessment of pump efficiency, pressure loss and other indicators in various operating modes. The results allow us to draw conclusions about the operation of the pump under various loads and variable conditions. The simulated pump worked with seven different liquids pumped in chemical tankers: ethyl alcohol, N-propyl alcohol, phenol, chloroform, castor oil, 55% nitric acid and water. After this, a neural network was created using the MATLAB/Neural Network Fitting Tool application. The input data of the network were volumetric flow, pressure, shaft power, torque and suction pressure. The output value was the pump efficiency, the value of which was estimated for each fluid. The root mean square error of approximation was very close to zero. According to these results, the artificial neural network showed satisfactory results for predicting the efficiency of the centrifugal cargo pump of the Ivan Poddubny type chemical tanker; therefore, it can be used in ship information and measurement systems. Overall, this paper represents a valuable research contribution to the field of modeling horizontal centrifugal pumps using Simulink that can be useful to engineers and researchers involved in the design and optimization of these pumps.

Analysis and optimization of injection characteristics and comprehensive performance of low GWP refrigerant HP-1 in high temperature heat pump systems

In the context of low-GWP refrigerants becoming a research hotspot, the environmentally friendly refrigerant HP-1 with independent intellectual property rights in China has demonstrated significant advantages in fields such as data centers and 5G base stations. However, there are few applied studies in the field of high-temperature heat pumps (HTHPs), therefore, in this study, HP-1 was utilized in HTHP system and this process was combined with the injection technology. It has been proven to be an effective approach for performance improvement. The injection characteristics of HP-1-based HTHP were analyzed and optimized with a focus on safety, stability, and efficient operation. The application advantages of HP-1 were compared and analyzed in terms of thermodynamic performance and Total Equivalent Warming Impact. The results indicated that there were three types of characteristic injection pressures based on system performance, corresponding to the maximum coefficient of performance (COP), the lowest electronic expansion valve inlet refrigerant temperature, and the lowest exhaust temperature of the compressor. Further, the corresponding control equations for injection pressure were obtained. Based on the safety injection pressure, the optimal COP under injection pressure could effectively improve the COP of the system by 2.1–5.2 %, and the exhaust temperature also increased by 6.1–10.1 %. When the temperature of the heat source was 50 °C and the target heating temperature was 120 °C, the heating capacity of HP-1 increased by 10.8 % compared with that of R245fa, the COP of the system increased by 2.7 %, and the volume heating capacity increased by 10.3 %. Moreover, the emission reduction effect of HP-1 was significant, and the carbon dioxide emissions were reduced by 15.4–39.1 %. The analysis shows that HP-1 exhibits better performance and environmental characteristics than HFC-245fa. This study is of guiding significance to improve the thermodynamic performance of HTHP, for the safe and efficient operation and energy saving and emission reduction in the industrial field.

Data-based, high spatiotemporal resolution heat pump demand for power system planning

Decarbonizing the residential building sector by replacing gas boilers with electric heat pumps will dramatically increase electricity demand. Existing models of future heat pump demand either use daily heating demand profiles that do not capture heat pump use or do not represent sub-national heating demand variation. This work presents a novel method to generate high spatiotemporal resolution residential heat pump demand profiles based on heat pump field trial data. These spatially varied demand profiles are integrated into a generation, storage, and transmission expansion planning model to assess the impact of spatiotemporal variations in heat pump demand. This method is demonstrated and validated using the British power system in the United Kingdom (UK), and the results are compared with those obtained using spatially uniform demand profiles. The results show that while spatially uniform heating demand can be used to estimate peak and total annual heating demand and grid-wide systems cost, high spatiotemporal resolution heating demand data is crucial for spatial power system planning. Using spatially uniform heating demand profiles leads to 15.1 GW of misplaced generation and storage capacity for a 90% carbon emission reduction from 2019. For a 99% reduction in carbon emissions, the misallocated capacity increases to 16.9-23.9 GW. Meeting spatially varied heating load with the system planned for uniform national heating demand leads to 5% higher operational costs for a 90% carbon emission reduction. These results suggest that high spatiotemporal resolution heating demand data is especially important for planning bulk power systems with high shares of renewable generation.

Mid-infrared idler-resonant optical vortex parametric oscillator based on MgO:PPLN

We present a high beam quality, mid-infrared, wavelength tunable, idler-resonant optical vortex parametric oscillator based on a single-grating MgO-doped periodically poled lithium niobate (MgO:PPLN) crystal. The compact, plane-concave cavity used in this work enabled transfer of the orbital angular momentum (OAM) of the pump field to the idler field, to deliver high beam quality, mid-infrared vortex beam emission with measured M2 factors of 2.2 in both orthogonal directions. The wavelengths of the signal (which had a TEM00/Gaussian-like spatial profile) and the idler vortex outputs could be tuned across the ranges 1.505–1.566 µm and 3.318–3.628 µm, respectively, by changing the MgO:PPLN crystal temperature in the range 25 to 200℃. We also investigate the mechanism of OAM transfer within the idler-resonant MgO:PPLN optical parametric oscillator (OPO) by tuning the cavity length. Here, we find that the OAM of the pump beam can be selectively transferred to the signal field by simply extending the cavity length. The maximum measured signal and idler vortex output energies were 3.3 mJ and 1.1 mJ, respectively, and were achieved using both compact and extended cavities at a pump energy of 21 mJ.

Unsteady Cavitation Analysis of the Centrifugal Pump Based on Entropy Production and Pressure Fluctuation

A numerical method using combined detached-eddy simulation (DES) and a cavitation model considering the rotation effect is used for unsteady cavitation flow field of the centrifugal pump. A closed-type pump test system was established to obtain the pump performance and pressure pulsation characteristics under different flow rates and cavitation condition, which provide boundary conditions and verification of calculations. Based on the calculation results of the unsteady flow field of the centrifugal pump cavitation, the entropy generation analysis of the flow field and an analysis of the pressure fluctuation characteristics were carried out. Then, we tried to reveal the relationship between cavitation and the deterioration of the centrifugal pump performance and the generation of the unstable operation excitation force. The internal energy loss is mainly concentrated in the impeller, volute, and pump cavity area, which accounts for more than 85% of the total entropy generation. The characteristic frequency of a Strouhal number of about 0.333 appears at the volute tongue due to the cavitation flow spread downstream.

Polarization-dependent intensity ratios in double resonance spectroscopy.

Double Resonance is a powerful spectroscopic method that unambiguously assigns the rigorous quantum numbers of one state of a transition. However, there is often ambiguity as to the branch (ΔJ) of that transition. Spectroscopists have resolved this ambiguity by using the dependence of the double resonance intensity on the relative polarization directions of pump and probe radiation. However, published theoretical predictions for this ratio are based upon a weak (i.e., non-saturating) field approximation. This paper presents theoretical predictions for these intensity ratios for cases where the pump field is strongly saturating in the two limits of transitions dominated by homogeneous or of inhomogeneous broadening. Saturation reduces but does not eliminate the magnitude of the polarization effect (driving the intensity ratio closer to unity) even with strong pump saturation. For the case of an inhomogeneously broadened line, such as when Doppler broadened linewidth dominates over the power-broadened homogeneous line width, a large fraction of the low pump power polarization anisotropy remains. This paper reports predicted polarization ratios for both linear and circular pump and probe field polarizations. The present predictions are compared with experimental measurements on CH4 ground state → ν3 → 3ν3 transitions recently reported by de Oliveira et al.63 and these are in better agreement than with the weak field predictions.

Single-longitudinal-mode lasing based on enhanced scattering in eccentric-hole microstructured optical fiber resonators

In this paper, we propose a dual-core eccentric-hole fiber (DCEHF) microresonator to achieve single-longitudinal-mode (SLM) laser emission based on enhanced pump light field induced by scattering effect of the two fiber cores. The directional dependences of the scattered pump field distribution on incident angle as well as overlap integrals between scattered pump light fields and WGMs have been theoretical investigated, and the calculation results show that when the incident angle of the pump light is close to 180°, significant discrepancies would occur in the overlap integrals between WGMs and the scattered field. And consequently, specific mode having the largest overlap integral would outperform through the mode competition process to excite SLM lasing. We have experimentally obtained SLM lasing emission when the DCEHF-based microresonator is rotated by 206°, which is in good accordance with our calculation results. Additionally, experimental observation of the output laser spectrum shows that the proposed fiber microcavity supports highly stable SLM laser emission. The proposed microresonator based on DCEHFs possesses several desirable merits such as compact size, good laser stability, single-mode operation, and good compatibility with existent fiber-optic systems, which make it a good candidate for applications as functional photonic device in future micro-optics systems.

Second-order coherence across the Brillouin lasing threshold

Brillouin–Mandelstam scattering is one of the most accessible nonlinear optical phenomena and has been widely studied since its theoretical discovery one hundred years ago. The scattering mechanism is a three-wave-mixing process between two optical fields and one acoustic field and has found a broad range of applications spanning microscopy to ultra-narrow-linewidth lasers. Building on the success of utilizing this nonlinearity at a classical level, a rich avenue is now being opened to explore Brillouin scattering within the paradigm of quantum optics. Here, we take a key step in this direction by employing quantum optical techniques yet to be utilized for Brillouin scattering to characterize the second-order coherence of Stokes scattering across the Brillouin lasing threshold. We use a silica microsphere resonator and single-photon counters to observe the expected transition from bunched statistics of thermal light below the lasing threshold to Poissonian statistics of coherent light above the threshold. Notably, at powers approaching the lasing threshold, we also observe super-thermal statistics, which arise due to instability and a “flickering” in and out of lasing as the pump field is transiently depleted. The statistics observed across the transition, including the “flickering,” are a result of the full nonlinear three-wave-mixing process and cannot be captured by a linearized model. These measurements are in good agreement with numerical solutions of the three-wave Langevin equations and are well demarcated by analytical expressions for the instability and the lasing thresholds. These results demonstrate that applying second-order-coherence and photon-counting measurements to Brillouin scattering provides new methods to advance our understanding of Brillouin scattering itself and progress toward quantum-state preparation and characterization of acoustic modes.

Pump-probe response and four-wave mixing in quantum dot exciton-biexciton – metal nanoparticle hybrid

We investigate theoretically the pump-probe response and the four-wave mixing spectrum in a hybrid system composed of a semiconductor quantum dot coupled to a spherical metal nanoparticle including both ground to exciton and exciton-biexciton transitions. We use a density matrix methodology for the calculation of the absorption/gain, dispersion and four-wave mixing spectra and examine their spectral characteristics, for different interparticle distances and under different pump field detuning conditions with respect to the one-photon and the two-photon resonance transitions. We also analyze the form of the spectra using a metastate theory, a description based on the coupling between the excitonic and the plasmonic transitions, while the dressed-state picture is applied in order to predict the positions at which the spectral resonances arise on the spectra.

One-Step Implementation of Collective Anti-Blockade in a Rydberg Ring

In contrast to Rydberg blockade, Rydberg anti-blockade allows multiple atoms to be simultaneously excited in the presence of significant nonlocal interactions and can lead to distinct phenomena and applications. This inspires us to examine here general conditions, numerical verifications, and realistic restrictions regarding the collective anti-blockade excitations of N Rydberg atoms equally arranged along a ring. We find that by adjusting the detuning of a pump field to compensate for nonlocal interactions between one atom and all others, it is viable to realize resonant excitations of N atoms but suppress far-detuned excitations of N−1 and fewer atoms under different conditions for an odd and an even number of atoms. Population dynamics of this Rydberg ring further show that one-step anti-blockade implementation can be attained at a cutoff time of the pump field, which increases quickly with the number of atoms. Hence, roughly perfect anti-blockade excitations are attainable only for a not-too-large N due to inevitable spontaneous Rydberg decay.

Fluid-induced vibration analysis of centrifugal pump including rotor system based on Computational Fluid Dynamics and Computational Structural Dynamics coupling approach

The flow-induced vibration of centrifugal pump under the effect of stator-rotor interaction are studied by Computational Fluid Dynamics method and Computational Structural Dynamics method based on the principle of one-way decomposition fluid-structure interaction. Firstly, the unsteady flow characteristics in centrifugal pump are studied by adopting the Computational Fluid Dynamics method, the numerical model of the whole flow field of the centrifugal pump is established, and the pulsating pressure characteristics of volute and impeller in the centrifugal pump are analyzed. The accuracy of the flow field modeling method and calculation method in this paper is verified by external characteristic test. Secondly, the vibration characteristic test of centrifugal pump is carried out, and the structural dynamic model and boundary conditions of centrifugal pump are verified and corrected in the modal test. Finally, the flow-induced excitation calculated by the flow field is simultaneously applied to the structural dynamics model of the centrifugal pump according to different transmission ways, and the flow-induced vibration of the whole centrifugal pump including the rotor system is calculated and analyzed by the Computational Structural Dynamics method in conjunction with rotor dynamics. Compared with the vibration test results, the validity of the flow-induced vibration calculation method of centrifugal pump in this paper is verified. The results show that under the influence of stator-rotor interaction effect, the blade passing frequency and shaft frequency are the main characteristic frequencies of pressure pulsation and dynamic response in the centrifugal pump.

Investigation of cavitation and flow characteristics of tip clearance of bidirectional axial flow pump with different clearances

With the increasing application of bidirectional axial pump, it is necessary to study the flow and cavitation characteristics of bidirectional pump. In this paper, the cavitation and flow characteristics of the tip clearance under different clearances and different cavitation numbers of the S-hydrofoil bidirectional axial flow pump were studied by combining experimental and numerical simulation methods under reverse operation conditions. The section of the bidirectional pump was experimentally studied by high-speed photography and pressure pulsation. Based on the method of RANS, the SST-CC turbulence model and ZGB cavitation model were used to simulate the clearance cavitation of the bidirectional pump, and the cavitation morphology, velocity distribution, clearance vortex structure and energy distribution of blade tip clearance were investigated. The study reveals the flow characteristics of the clearance flow field of the bidirectional pump, and provides reference for the design and operation of it.

Photon pumping, photodissociation and dissipation at interplay for the fluorescence of a molecule in a cavity

We introduce a model description of a diatomic molecule in an optical cavity, with pump and fluorescent fields, and electron and nuclear motion are treated on equal footing and exactly. The model accounts for several optical response temporal scenarios: A Mollow spectrum hindered by electron correlations, a competition of harmonic generation and molecular dissociation, a dependence of fluorescence on photon pumping rate and dissipation. It is thus a general and flexible template for insight into experiments where quantum photon confinement, leakage, nuclear motion and electronic correlations are at interplay.

Photonic negative differential transistor based on cavity polaritons

We theoretically provide a scheme for realizing a photonic negative differential transistor (NDT) by using a two-port asymmetric system with cavity exciton polaritons. In such a hybrid optomechanical system, the transmission of the probe light can be completely regulated by the pump field. Interestingly, the resonance transmission curve of probe light has a negative (positive) slope to the pump intensity, which depends on the coupling among excitons, photons and phonons. Therefore, the probe transmission exhibits the characteristic of negative (positive) differential transistors. The transmission spectrum of probe fields is modified by Stokes and anti-Stokes scattering effects, resulting in the output probe light be either attenuated or amplified. Moreover, we find that the transmission of pump fields has a bistability characteristic with appropriate parameters due to nonlinear effects. Our results open up exciting new possibilities for designing a photonic NDT, which may be applied to implement polariton integrated circuits.

Effect of Blade Twist on The Flow Characteristics of Gas-Liquid Two-Phase Flow in a Spiral Axial Flow Pump

The mixing of oil and gas forms the foundation of deep-sea oil and gas extraction and transportation. However, traditional conveying equipment has low efficiency and high failure rates. In this study, a spiral axial flow gas and liquid multiphase pump was used as the base model. The Eulerian multiphase flow model and RNG turbulence model were used for numerical simulations to analyze the internal flow field of the multiphase pump. A modification scheme was proposed to twist the airfoil shape and create a twisted vane. The twisted blade with the center of the hub-side flange chord length as the twisting center was twisted in the counterclockwise direction to help reduce the relative volume of gas in the flow channel. When the twisted vane with the hub-side airfoil type trailing edge point as the twisting center was twisted in the suction side direction, it helped to accelerate the movement of the gas-liquid mixture at the trailing edge of the back of the vane and further reduced the low velocity zone at the back of the vane. When the twist center is located at the hub side wing type trailing edge point of the twist vane, the twist degree is 0.214. This results in the maximum head and efficiency of the pump, improves gas phase aggregation phenomenon, and enhances the performance of the multiphase pump.