Pump Frequency Research Articles

A novel perspective of addressing the hydraulic dynamic imbalance in district heating network: The application of nonlinear programming

Hydraulic balance within the heating system's pipeline network is essential for efficient operation. Hydraulic imbalances can result in increased energy consumption and heat loss. Accordingly, a new dynamic hydraulic model has been developed, leveraging the topological structure of the network. This model incorporates the nonlinear constraints associated with flow coupling between electric valves and variable frequency pumps, with the objective of minimizing energy used in pump operation. It determines the optimal pump frequency and valve settings for operational adjustments. The model's predictive accuracy was validated using real operational data from a campus heating system. Additionally, it calculates the campus's ideal load and evaluates the potential for energy savings. Three adjustment strategies were established based on different temporal scales: hourly, day-and-night, and daily. Findings indicate that the optimized system offers substantial energy savings, particularly the hourly adjustment, which reduces pump energy consumption by 38.2 % and total system flow by 9.0 %. The day-and-night variable frequency was the next most effective, reducing pump energy consumption by 32.8 %, and total system flow by 7.6 %. The daily variable frequency strategy showed the least energy savings, with pump energy consumption by 25.0 %, and total system flow by 5.5 %. This dynamic hydraulic regulation optimization model serves as a valuable tool for developing intelligent heating systems.

Raman-phonon-polariton condensation in a transversely pumped cavity

Phonon polaritons are hybrid states of light and matter that are typically realised when optically active phonons couple strongly to photons. We suggest a new approach to realising phonon polaritons, by employing a transverse-pumping Raman scheme, as used in experiments on cold atoms in optical cavities. This approach allows hybridisation between an optical cavity mode and any Raman-active phonon mode. Moreover, this approach enables one to tune the effective phonon–photon coupling by changing the strength of the transverse pumping light. We show that such a system may realise a phonon-polariton condensate. To do this, we find the stationary states and use Floquet theory to determine their stability. We thus identify distinct superradiant and lasing states in which the polariton modes are macroscopically populated. We map out the phase diagram of these states as a function of pump frequencies and strengths. Using parameters for transition metal dichalcogenides, we show that realisation of these phases may be practicably obtainable. The ability to manipulate phonon mode frequencies and attain steady-state populations of selected phonon modes provides a new tool for engineering correlated states of electrons.

Exceptional points in the microcavity with phonon pump enhance the transparency and slow light

We theoretically investigated optomechanically induced transparency (OMIT) and slow light in a microcavity optomechanical system containing three nanoparticles, where the pump-probe field drives the cavity and a weak phonon pump drives the mechanical resonator. When the phonon pump frequency matches the pump-probe field frequency difference, adjusting the phonon pump's amplitude and phase can result in the transparency window exceeding unity. Tuning the relative positions of nanoparticles can periodically steer the system to exceptional points (EPs), further enhancing and modulating the transparency window. Furthermore, the phonon pump causes the phase dispersion at the transparency window to become highly steep, resulting in a large value and tunable group delay. Notably, when the system is at EPs, the slow light can be enhanced by approximately two times compared to when the system is not at EPs. Our research demonstrates a way to control optical transmission with potential applications in quantum communications and optical buffers.

Effective nonlinearity of trigonal BaGa2GeS6

Implementing second-harmonic and sum-frequency generation processes with a specially oriented sample, we determine the magnitude and sign of the nonlinear optical coefficients d11, d22, and d31 of the recently developed trigonal BaGa2GeS6. We conclude that it is a viable alternative to the widely used chalcopyrite AgGaS2 for 1 µm pumped frequency downconversion to the mid-IR spectral range.

Frequency stabilization of self-sustained oscillations in a sideband-driven electromechanical resonator

We present a method to stabilize the frequency of self-sustained vibrations in micromechanical and nanomechanical resonators. The method refers to a two-mode system with the vibrations at significantly different frequencies. The signal from one mode is used to control the other mode. In the experiment, self-sustained oscillations of micromechanical modes are excited by pumping at the blue-detuned sideband of the higher-frequency mode. Phase fluctuations of the two modes show near-perfect anticorrelation. They can be compensated in either of the modes by a stepwise change of the pump phase. The phase change of the controlled mode is proportional to the pump phase change, with the proportionality constant independent of the pump amplitude and frequency. This finding allows us to stabilize the phase of one mode against phase diffusion using the measured phase of the other mode. We demonstrate that phase fluctuations of either the high-frequency mode or the low-frequency mode can be significantly reduced. The results open new opportunities in generating stable vibrations in a broad frequency range via parametric down-conversion in nonlinear resonators. Published by the American Physical Society 2024

DRQN-based global optimal control of air conditioning water system

The intelligent control of the air conditioning water system, a critical component of HVAC systems, plays a crucial role in reducing building energy consumption. Reinforcement learning (RL), an emerging interactive learning method capable of self-optimization according to environmental changes, has been widely applied in the field of HVAC control. This paper focuses on an air conditioning water system with chiller group control. Initially, a load-based sequencing control strategy is adopted, and deadband ranges are set based on empirical knowledge to coordinate the sequencing control of multiple devices. Subsequently, cooling load, wet-bulb temperature, and the number of chillers are used as the state space. By incorporating the implicit temporal information associated with these changes, the Deep Recurrent Q-Network (DRQN) is introduced to effectively leverage historical data for optimizing operational parameters such as chiller supply water temperature, pump frequency, and cooling tower fan speed. Experimental results show that compared with traditional rule-based control and Deep Q-Network (DQN) control, the proposed control framework achieves energy savings of 20.38%-24.59% and 1.82%-3.48%, respectively, under different sequencing control strategies.

Enhanced temperature regulation in compound heating systems: Leveraging guided policy search and model predictive control

With the widespread application of solar-energy-air-source heat pump composite heating, optimizing the regulation of air temperature in heating zones, enhancing system thermal comfort, and reducing energy consumption have become crucial. To ensure residential comfort while minimizing HVAC system energy costs, a control method combining guided policy search (GPS) with model predictive control (MPC) is proposed for composite heating systems. This method replaces state estimation in MPC with policy search and substitutes the offline trajectory optimization used in guided policy search with MPC, thus integrating the strengths of both approaches. This strategy not only improves control precision but also reduces energy consumption and enhances system robustness. The GPS-MPC control algorithm was validated against reinforcement learning and MPC. A simulation model was developed and validated on a real physical platform. Simulations compared the control effects of on-off control and MPC on pump frequency, flow rate, stratified thermal storage tank temperature, component, and system energy consumption. The data results indicate that the GPS-MPC algorithm offers superior predictive accuracy, efficiency, and robustness in composite heating control systems compared to conventional methods. Under the GPS-MPC strategy, indoor temperature fluctuations, pump frequency response speed, and energy consumption were significantly improved, with temperature fluctuation limited to only 0.8 °C, and the system achieving energy savings of over 12 %.

Operational characteristics and performance optimizations of the organic Rankine cycle under different heat source/condensing environment conditions

The fluctuating heat sources and seasonal condensing environments are critical to the operation of Organic Rankine Cycle (ORC) under off-design conditions. This paper presents a comprehensive steady-state mathematical model developed using a newly built experimental platform. Focusing on the operational characteristics, including the evaporation pressure, condensation temperature, mass flow rate, and the performance of key equipment during the regulation of the expander, working fluid pump, and cooling water pump. Results show that the net efficiency initially increases before decreases, with both evaporation pressure and mass flow rate rising alongside the working fluid pump frequency. The quasi-two-stage single screw expander achieves an isentropic efficiency above 65 %. Additionally, flexible adjustments to the cooling water pump effectively regulate the cooling system, with timely cleaning of cooling pipelines enhancing net efficiency by up to 3.27 %. Optimization using the particle swarm algorithm improves system performance, achieving net efficiency enhancements of 1.8 % and 12.3 % under specific conditions. The novelty of this study lies in directly regulation of the expander, working fluid pump, and cooling water pump, significantly enhancing the off-design performance. This research provides valuable insights for researchers and designers, enabling flexible regulation of ORC operations to ensure efficient performance under varying conditions.

Optimizing The Pump Power and Frequencies of Raman Amplifiers for Gain Flatness

The Internet has become an indispensable part of daily life, accessible to anyone with coverage via smartphones or computers. Extending internet coverage to remote areas necessitates long-distance transmission, which requires optical amplifiers to combat signal degradation and dispersion between the transmitter and receiver. This challenge restricts the reach and bandwidth of long-distance telecommunications. Among optical amplifiers, the Raman amplifier (RA) stands out due to its lower noise gain advantage compared to other amplifiers. The RA shows promise in overcoming the limitations of long-distance telecommunications. Its gain can be controlled by adjusting the pump power or wavelength. This paper investigates the performance optimization of RA with the objective of enhancing its effectiveness in long-distance telecommunication systems. Using the Optiwave simulation tool, we conducted a series of experiments to optimize RA performance by varying pump power and frequency. The results, analyzed through a spectrum analyzer, demonstrate significant improvements in gain flatness post-optimization, with an observed enhancement of 1-1.5 dB. A comparative analysis of gain flatness before and after optimization highlights the RA's potential in mitigating long-distance communication limitations. These findings suggest that optimized RA can significantly improve bandwidth and signal quality, offering a viable solution for current and future telecommunication challenges.

High-Yield Expressed Human Ferritin Heavy-Chain Nanoparticles in K. marxianus for Functional Food Development.

The use of Generally Recognized as Safe (GRAS)-grade microbial cell factories to produce recombinant protein-based nutritional products is a promising trend in developing food and health supplements. In this study, GRAS-grade Kluyveromyces marxianus was employed to express recombinant human heavy-chain ferritin (rhFTH), achieving a yield of 11 g/L in a 5 L fermenter, marking the highest yield reported for ferritin nanoparticle proteins to our knowledge. The rhFTH formed 12 nm spherical nanocages capable of ferroxidase activity, which involves converting Fe2+ to Fe3+ for storage. The rhFTH-containing yeast cell lysates promoted cytokine secretion (tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and -1β (IL-1β)) and enhanced locomotion, pharyngeal pumping frequency, egg-laying capacity, and lifespan under heat and oxidative stress in the RAW264.7 mouse cell line and the C. elegans model, respectively, whereas yeast cell lysate alone had no such effects. These findings suggest that rhFTH boosts immunity, holding promise for developing ferritin-based food and nutritional products and suggesting its adjuvant potential for clinical applications of ferritin-based nanomedicine. The high-yield production of ferritin nanoparticles in K. marxianus offers a valuable source of ferritin for the development of ferritin-based products.

High repetition-Rate laser diode side-Pumped burst-mode Nd:YAG laser with enhanced output pulse uniformity

A theoretical and experimental investigation is conducted on a high repetition-rate side-pumped burst-mode Nd:YAG laser. The absorbed pumping power distribution and laser resonator are meticulously optimized to enlarge the area of the fundamental mode and improve thermal stability. With the 1 ms pumping duration and a pumping frequency of 10 Hz, the pulsed laser’s burst energy, peak power, and pulse width achieve 0.29 J, 347 kW, and 16 ns, respectively, with the Q-switched repetition rate of 50 kHz. The minimum coefficient of variation for the laser pulse train remains below 5 %. This study represents the first demonstration of a long-term reliable output from a high-energy, nanosecond-pulsed, side-pumped Nd:YAG burst laser operating at 50 kHz.

A cavalpulmonary assist device utilising impedance pumping enhanced by peristaltic effect.

Fontan procedure, the standard surgical palliation to treat children with single ventricular defects, causes systemic complications over years due to lack of pumping at cavopulmonary junction. A device developed specifically for cavopulmonary support is thus considered, while current commercial ventricular assist devices (VAD) induce high shear rates to blood, and have issues with paediatric suitability. To demonstrate the feasibility of a small, valveless, non-invasive to blood and pulsatile rotary pump, which integrates impedance and peristaltic effects. A prototype pump was designed and fabricated in-house without any effort to optimise its specification. It was then tested in vitro, in terms of effect of pumping frequency, background pressure differences and pump size on output performance. Net flow rate (NFR) and maximum pressure head delivery are both reasonably linearly dependent on pumping frequency within normal physiological range. Positive linearity is also observed between NFR and the extent of asymmetric pumping. The device regulates NFR in favourable pressure head difference and overcomes significant adverse pressure head difference. Additionally, performance is shown to be insensitive to device size. The feasibility of the novel rotary pump integrating impedance and peristaltic effects is demonstrated to perform in normal physiological conditions without any optimisation effort. It provides promising results for possible future paediatric cavopulmonary support and warrants further investigation of miniaturisation and possible haemolysis.

Biomarker-based text messages to promote lactation success in mothers of critically Ill infants: a randomized controlled pilot study.

Infrequent breast pumping limits mother's own milk production in mothers of infants admitted to the neonatal intensive care unit. We aimed to determine the feasibility and benefit of biomarker-based personalized text messages on pumping frequency and milk sodium levels. A secondary aim examined lactation outcomes. In this randomized controlled pilot study, 51 mothers were randomized to receive personalized text messages regarding pumping frequency or standard care. There were no differences in pumped milk volume or sodium level, however, there was a trend towards the intervention group pumping more frequently, which was significant on day 5 (p = 0.035), and they lactated nearly 9 days longer. Post-hoc analysis found the intervention group tended to be more likely to pump ≥ 500 mL by day14 (p = 0.08), a marker of long-term lactation success. Personalized biomarker-based text messages are feasible and may support lactation in mothers of critically ill infants.

Hybrid model-free control based on deep reinforcement learning: An energy-efficient operation strategy for HVAC systems

At present, most optimization objectives of heating, ventilation, and air-conditioning (HVAC) systems focus on the local optimization of equipment during cooling hours, usually ignoring the importance of the end conditions. In addition, traditional control methods may not perform well in complex or dynamic systems. Therefore, in this study, a hybrid model-free control (HMFC) strategy was developed that combines deep reinforcement learning (DRL) with L-BFGS-B and expert knowledge to improve its ability to cope with complex system environments. This strategy was used to optimize the cooling and heating periods of a groundwater source heat pump system in a bitterly cold region of China throughout the year, considering the end-of-system conditions. L-BFGS-B optimized the fresh-air ratios for the end air-handling unit, whereas DRL achieved global optimization of the heat pump outlet temperature, air-conditioning water circulation pump frequency, and submersible-pump frequency. To verify the effectiveness of the strategy, a simulation platform was built based on actual data and device parameters, and the simulation results of HMFC and model predictive control (MPC) were output, compared, and analyzed with data of the system measured in 2022 under expert rule-based manual control (RBC). The results show that HMFC was 7.38 % and 9.38 % more energy efficient than RBC during heating hours, respectively. HMFC was 24.26 % more energy efficient than RBC and 10.03 % more energy efficient than MPC during cooling hours. Moreover, the distribution of the system coefficient of performance under the HMFC method was more concentrated in the higher range, indicating that the proposed HMFC can save energy savings. Thus, it is a feasible optimization scheme for buildings without a large number of historical data. Finally, the strategy was applied to a real engineering experimental analysis, and the engineering practice results show that the strategy is robust and practical.

Cross-phase modulation induced microcomb generation in the normal-dispersion region.

Microcomb generation in the normal-dispersion region usually requires specially designed microresonators with mode interactions, increasing the complexity of device design and control. Here we demonstrate a novel, to the best of our knowledge, scheme of frequency comb generation by bidirectionally pumping an ordinary normal-dispersion microresonator. The cross-phase modulation from the counter-propagating light reshapes the cavity response, facilitating the emergence of modulational instability for comb initiation. By properly adjusting the pump power ratio and frequency detuning in two directions, frequency combs can be formed at any pumped resonance. The proposed method provides a universal pathway to flexible microcomb generation in the normal-dispersion regime.

Laser pulse induced second- and third-harmonic generation of gold nanorods with real-time time-dependent density functional tight binding (RT-TDDFTB) method.

In this study, we investigate second- and third-harmonic generation processes in Au nanorod systems using the real-time time-dependent density functional tight binding method. Our study focuses on the computation of nonlinear signals based on the time dependent dipole response induced by linearly polarized laser pulses interacting with nanoparticles. We systematically explore the influence of various laser parameters, including pump intensity, duration, frequency, and polarization directions, on harmonic generation. We demonstrate all the results using Au nanorod dimer systems arranged in end-to-end configurations, and disrupting the spatial symmetry of regular single nanorod systems is crucial for second-harmonic generation processes. Furthermore, we study the impact of nanorod lengths, which lead to variable plasmon energies, on harmonic generation, and estimates of polarizabilities and hyper-polarizabilities are provided.

Design and testing of a high power piezo pump for hydraulic actuation

Traditional valve-controlled hydraulic cylinders are usually very inefficient due to power loss through the control valve. An efficient alternative architecture is to distribute power electrically rather than hydraulically to a group of cylinders and drive each cylinder via individual servomotor-driven pumps. This arrangement is called electrohydrostatic actuation. Such actuators are currently available for power ratings of several hundred watts or greater, but not in the sub-100 W range. This paper details the design, simulation and testing of a piezopump which is intended to address this gap. The motivation is for aerospace applications, and in particular accessory actuators used in the landing gear system. The 10–100 W range is a high-power output for a piezopump, and to achieve this a novel design using disc-style reed valves was developed to allow pumping frequencies above 1 kHz. These high frequencies necessitated the development of custom power electronics capable of delivering 950 V peak-peak sine wave excitation to a largely capacitive load. Experimental results show that the piezopump is capable of delivering over 30 W of hydraulic power, and at no-load can deliver up to 2 L/min of flow at 1250 Hz. Future development includes a transition to multi-cylinder pumps, and improved reed-valve modelling to improve the accuracy of simulated performance.

Mitigating vibration from building systems in a second-floor laboratory

A second-floor laboratory reported excessive vibrations that were impacting the calibration of microscopes, as well as human comfort. Based on a review of the building floor plans and discussions with the Design-Build team, potential vibration sources were narrowed to various MEP equipment in the first-floor mechanical room, rooftop, and outdoor utility pad. Vibration measurements were collected in the laboratory and near each piece of mechanical equipment as the equipment was turned ON and OFF to determine its vibration impact on the laboratory. The narrowband frequency data indicated that the rotational frequency of the ceiling-mounted hot water pumps coincided with the frequencies of excessive vibration in the lab. Vibration isolation for the hot water pumps and surrounding piping and equipment was reviewed, and recommendations were provided based on ASHRAE guidance to minimize vibration propagation to the laboratory.

Optimasi Jaringan Pipa Sumur ESP Pada Manifold A dan Manifold Satelite untuk Meningkatkan Laju Aliran Minyak dan Analisis Perubahan Tekanan di Lapangan J

The wells in Field J, using Electrical Submersible Pumps (ESP), have replaced their natural flow operations. To optimize this ESP well and pipeline network, the research focuses on adjusting the ESP pump frequency within the Pipesim simulator, increasing it to enhance oil flow rates. This study employs a quantitative approach, where field data is analyzed and input into a simulation model that replicates real-world conditions. The analysis encompasses changes in flow rates and pressures, comparing the base case to post-optimization simulations. The results indicate a substantial increase in the initial oil flow rate from 578 STB to 720 STB/d, with an increase of 142 STB/d, when the pump frequency is raised to 60 Hz. This frequency adjustment significantly boosts pump discharge pressure, providing the added energy needed to transport fluid to the surface. Keyword: esp; pipeline network; production optimization; production simulation

Low-noise short-wavelength pumped frequency downconversion for quantum frequency converters

We present a highly efficient low-noise quantum frequency converter from the visible range to telecom wavelengths, combining a pump laser at intermediate frequency resonantly enhanced in an actively stabilized cavity with a monocrystalline bulk crystal. A demonstrator for photons emitted by nitrogen-vacancy-center qubits achieves 43% external efficiency with a noise photon rate per wavelength (frequency) band of 2 s−1/pm(17 s−1/GHz) – reducing the noise by two orders of magnitude compared with current devices based on periodically poled crystals with waveguides. With its tunable output wavelength, this device enables the generation of indistinguishable telecom photons from different network nodes and is, as such, a crucial component for a future quantum internet based on optical fiber.