Critical Pump Research Articles

Resonantly enhanced polariton wave mixing and parametric instability in a Floquet medium.

We introduce a new theoretical approach for analyzing pump and probe experiments in non-linear systems of optical phonons. In our approach, the effect of coherently pumped polaritons is modeled as providing time-periodic modulation of the system parameters. Within this framework, propagation of the probe pulse is described by the Floquet version of Maxwell's equations and leads to phenomena such as frequency mixing and resonant parametric production of polariton pairs. We analyze light reflection from a slab of insulating material with a strongly excited phonon-polariton mode and obtain analytic expressions for the frequency-dependent reflection coefficient for the probe pulse. Our results are in agreement with recent experiments by Cartella et al. [Proc. Natl. Acad. Sci. U. S. A. 115, 12148 (2018)], which demonstrated light amplification in a resonantly excited SiC insulator. We show that, beyond a critical pumping strength, such systems should exhibit Floquet parametric instability, which corresponds to resonant scattering of pump polaritons into pairs of finite momentum polaritons. We find that the parametric instability should be achievable in SiC using current experimental techniques and discuss its signatures, including the non-analytic frequency dependence of the reflection coefficient and the probe pulse afterglow. We discuss possible applications of the parametric instability phenomenon and suggest that similar types of instabilities can be present in other photoexcited non-linear systems.

Waste heat recovery at low temperature from heat pumps, power cycles and integrated systems – Review on system performance and environmental perspectives

Utilization of unused waste heat energy below 100 °C is a challenging effort. In spite of investing in energy retrieving technology, a considerable amount of heat energy is still dissipating to the surroundings. The recovery of LTWH through different technologies plays a pivotal role in several process industries and domicile application. Heat pumps are widely employed to retrieve low level heat energy and also aid in reducing greenhouse gas emission. Hybrid absorption-compression heat pump showed maximum of 95% waste heat recovery rate, where air-source and CO2 trans critical heat pump reduced energy consumption by 60–75% and centrifugal heat pumps generated 9700 kW capacity of heat. Most of the studies reported the effective performance of absorption heat pump units with heat source temperature lie in the range of 60–120 °C along with maximum energy and exergy production with minor irreversible energy loss. Nanofluids are emerging as a high-performance working fluid for heating and cooling applications. Silver/pentane nanofluids increased overall system efficiency and showed 14% less carbon footprint, which is considered as a most effective alternate to hazardous working fluids. The simultaneous production of potable water and electrical power generation through desalination system was reviewed. The techno-economic assessment of using heat pumps in low grade energy recovery and its integrated prototype were presented in this paper together with the environmental impact of working fluids used in the heat pumps and thermodynamic cycles.

New water pump station for Calgary

To satisfy both current and future demands for safe and reliable drinking water, the City of Calgary has recently embarked on a Can$35 million project to replace the most critical water pump station in the city.

General Approach to Modeling of Non-Contact Seals and Their Effect on the Dynamics of a Centrifugal Machine Rotor

There is a constant demand for higher equipment parameters, such as pressure of a sealing medium and shaft rotation speed. However, as the parameters rise it becomes more difficult to ensure hermetization efficiency. Moreover, sealing systems affect the overall operational safety of the equipment, especially vibratory. Non-contact seals are considered as hydrostatodynamic supports that can effectively damp rotor oscillations. Models of an impulse and a groove seals, models of rotor-seals system and rotor-auto-unloading system, model of a shaftless pump are studied to evaluate an effect of these sealing systems on oscillatory characteristics of rotor. Analytical dependencies for computation the dynamic characteristics of impulse seals, hydromechanical systems rotor-seals and rotor-auto-unloading, as well as shaftless pumps are obtained. These dependencies describe the radial-angular vibrations of a centrifugal machine rotor in seals-supports. Equations for computation the amplitude-frequency characteristics are given. The directions of improving the оperational safety of critical pumping equipment by purposefully increasing the rigidity of non-contact seals that leads to higher rotor vibration stability have been determined.

Bi4Br4-based saturable absorber with robustness at high power for ultrafast photonic device

Saturable absorption may be induced at critical pumping power by nonlinear optical effects of nanomaterials, thereby making it possible to generate a high-power ultrafast laser. Recently, Bi4Br4 is theoretically predicted to be a member of topological insulators and is expected to be a promising candidate for saturable absorbers (SAs). We show here that Bi4Br4 features a large modulation depth of 42.3%. The Bi4Br4-based SA enables mode-locking operation at the near-infrared range, as demonstrated here by a 1.5 μm fiber laser with a signal-to-noise ratio (SNR) of 90 dB and a pulse duration of 172 fs. Moreover, the robustness of the Bi4Br4-based SA at relatively high power is of particular interest, which can be proved by a laser's stable operation state. The strong optical nonlinearity and robustness provided by Bi4Br4 may arouse a growing upsurge in the innovation of high-power ultrafast photonic devices and further development of photon applications.

Improvement of the Theis unsteady well flow model with infiltration recharge in a phreatic aquifer

The recharge and discharge of groundwater are mainly vertical surface infiltration recharge, evaporation discharge (evaporation can be shown as negative value of infiltration) and lateral surface water recharge and discharge. One of the most basic problems in hydrogeology is the evaluation criteria of sustainable exploitation of groundwater, which involves the increment of recharge and the decrease of discharge. Therefore, the prediction model of groundwater exploitation must include the above two kinds of recharge and discharge factors, otherwise the evaluation of groundwater cannot meet the requirements. However, the classic Theis unsteady well flow model (1935) only involves the recharge and discharge of the side boundary, and does not considers the surface infiltration recharge of the upper boundary, even when groundwater is pumped near the river. In this way, the analytical model cannot be basically used for prediction, and can only be used for well flow test to obtain the aquifer parameters in dry season. Therefore, the goal of this paper is to develop the Theis unsteady well flow model with surface infiltration recharge. For the problem of phreatic flow, the equation of groundwater flow cannot be established by using head as the dependent variable in a confined aquifer. We use the potential function of the second linearization method to establish groundwater flow equation in the phreatic aquifer. For the solution of the generalized mathematical model of the complex hydrogeological problem with rainfall infiltration and a pumping well, we adopt the method of decomposing it into several simple sub-models and synthesizing them into the solution of the original complex mathematical model. Based on the principle of mass conservation and assuming that the seepage obeys the Darcy’s law and satisfies the Dupuit's assumptions, the differential equation of groundwater flow is established. Then, for the well flow problem with uniform and stable infiltration recharge in two parallel rivers and two kinds of strip regions formed by a river parallel to an impermeable boundary, the general equation of groundwater flow and several kinds of water table equations under specific conditions and their flux equations are obtained. In addition, the “boundary to boundary reflection method” is proposed and applied to solve the same problem in a strip of region between a river boundary in parallel to an impermeable boundary, which reduces many derivation processes. Finally, as a preliminary application of the above theoretical results, it is also an important application, that is, there is a pumping well near the river whose water quality cannot meet the requirements, and the critical flux equation of the pumping well is calculated on the premise of not absorbing the river water. The important and concise relation equation is obtained. The equation can also be used to calculate the critical pumping rate of pumping wells in coastal areas without seawater intrusion. In this paper, the groundwater flow network diagram at a certain time in the process of unstable well flow under the above conditions is given. Compared with the flow network of well flow near the river, which is commonly seen in the literature, the flow network has obvious characteristics.

Pumping Well Layout Scheme Design and Sensitivity Analysis of Total Critical Pumping Rates in Coral Island Based on Numerical Model

Groundwater on small coral islands exists in the form of freshwater lenses that serve as an important water resource for local inhabitants and ecosystems. These lenses are vulnerable to salinization due to groundwater abstraction and precipitation variation. Determination of the sustainable yield from freshwater lenses is challenging because the uncertainties of recharge and hydrogeological characteristics make it difficult to predict the lens response to long-term pumping. In this study, nine pumping well layout schemes along a line are designed using the orthogonal experimental design method, and an optimal well layout scheme is determined by multi-index range analysis and comprehensive balance analysis method. The total critical pumping rates of the freshwater lens corresponding to different schemes are calculated by numerical simulation, and the sensitivity of the total critical pumping rates to hydrogeological parameters is analyzed. The results show that the calculation of the total critical pumping rates needs to be combined with the specific well layout scheme with consideration to the length of well screens, the number of wells and the distance between wells. The difference in total critical pumping rates between different schemes can be up to three times. The uncertainty of hydrogeological parameters has a great impact on the total critical pumping rates. Within the range of a 30% reduction in parameters, α and K are the key risk factors of pumping; within the range of a 30% increase in parameters, α, ne and K are the key risk factors; α-ne combined changes had the greatest impact. The management of freshwater lenses and the assessment of sustainable yield will continue to be important tasks for coral islands in the future, and this study can help with the sustainable exploitation of island freshwater lenses.

Ultrafast Modulations and Detection of a Ferro-Rotational Charge Density Wave Using Time-Resolved Electric Quadrupole Second Harmonic Generation.

We show the ferro-rotational nature of the commensurate charge density wave (CCDW) in 1T-TaS_{2} and track its dynamic modulations by temperature-dependent and time-resolved electric quadrupole rotation anisotropy-second harmonic generation (EQ RA-SHG), respectively. The ultrafast modulations manifest as the breathing and the rotation of the EQ RA-SHG patterns at three frequencies around the reported single CCDW amplitude mode frequency. A sudden shift of the triplet frequencies and a dramatic increase in the breathing and rotation magnitude further reveal a photoinduced transient CDW phase across a critical pump fluence of ∼0.5 mJ/cm^{2}.

Investigating Effect of Pumping Ratio on Effectiveness of Barrier Wells for Saltwater Intrusion: Lab-Scale Experiments and Numerical Modeling

Saltwater intrusion, leading to the salinization of fresh groundwater, is the most challenging problem in coastal regions. Saltwater pumping from a barrier well is widely applied to prevent saltwater intrusion. Owing to its easy installation, many studies have investigated saltwater pumping. However, quantitative relationships between the barrier and inland production wells have not been revealed. In this study, lab-scale experiments were conducted to examine the effectiveness of a barrier well on the possible flow rate of freshwater from a production well. Moreover, a two-dimensional numerical model was created and simulated under the same conditions as those used in the experiments to analyze the experimental results. Consequently, a critical pumping ratio of 1.9 was obtained. In the numerical simulation, it was confirmed that an upconing of highly concentrated saltwater toward the barrier well was observed when the pumping ratio was less than the critical ratio. In conclusion, there is a critical pumping ratio between the barrier and the production well, and saltwater intrusion can be controlled by keeping the pumping rates under the critical ratio. Although further studies have yet to be conducted on a practical scale, this study showed the potential of the pumping ratio control to manage saltwater intrusion.

Experimental and modeling investigation of pumping from a fresh groundwater lens in an idealized strip island

Groundwater lens floating on the seawater in surficial coastal aquifers is an important freshwater supply for small island inhabitants. This study addresses an unanswered, simple but important question for groundwater resources management in small islands: how much freshwater can be sustainably withdrawn from a groundwater lens in small islands. We derive an approximate analytical solution to describe the freshwater-seawater sharp interface profile in an idealized strip island subject to a pumping well located at the domain center to determine the critical or maximum allowable pumping rate that prevents saltwater upconing. A simple formula of the critical pumping rate is provided as a function of hydrogeologic parameters, including the recharge rate, densities, hydraulic conductivity and well penetrating depth. It shows that the critical pumping rate increases linearly with the recharge rate and decreases linearly with the hydraulic conductivity and the squared well penetrating depth. Laboratory visualization experiments and numerical simulations were conducted to validate the derived analytical solution. Results indicate that the maximum pumping rate can be as high as 50% of the total recharge for a single well located at the top of the domain center. Our solutions and results provide useful insights for sustainable groundwater management in small islands and can potentially render significant social and economic impact for inhabitants on small islands.

Laboratory Physical Experiments on the Saltwater Upconing and Recovery of Island Freshwater Lenses: Case Study of a Coral Island, China

The research of saltwater upconing is crucial for the development and utilization of island freshwater resources. In this paper, a laboratory physical experiment device was developed, and the saltwater upconing and recovery of island freshwater lenses were investigated using rainfall simulations and single-well and multi-well pumping tests with various pumping intensities. The results of the experiment revealed that: (1) The thickness of the freshwater lens increased continuously and linearly during the early stages of rainfall. As the rainfall continued, the upward trend slowed and eventually leveled off. (2) Under the same pumping duration, when the pumping intensity was less than the critical pumping intensity, the increasing height rate of the saltwater upconing increased linearly at a small gradient, and when the pumping intensity was greater than the critical value, the rising height rate of the saltwater upconing increased linearly at a large gradient. (3) Under the same pumping intensity conditions, the pumping duration of the multi-well was longer than that of the single-well pumping, and the pumping volume of the multi-well was also greater than that of the single-well pumping. The experiment results can provide support for the development and utilization of island freshwater lens.

Cavity-enhanced magnetometer with a spinor Bose–Einstein condensate

We propose a novel type of composite light–matter magnetometer based on a transversely driven multi-component Bose–Einstein condensate coupled to two distinct electromagnetic modes of a linear cavity. Above the critical pump strength, the change of the population imbalance of the condensate caused by an external magnetic field entails the change of relative photon number of the two cavity modes. Monitoring the cavity output fields thus allows for nondestructive measurement of the magnetic field in real time and we show that the sensitivity of the proposed magnetometer exhibits Heisenberg-like scaling with respect to the atom number. For state-of-the-art experimental parameters, we calculate the lower bound on the sensitivity of such a system to be of the order of fT –pT for a condensate of 104 atoms with coherence times on the order of several ms.

Many-body phases of a planar Bose-Einstein condensate with cavity-induced spin-orbit coupling

We explore the many-body phases of a two-dimensional Bose-Einstein condensate with cavity-mediated dynamic spin-orbit coupling. By the help of two transverse non-interfering, counterpropagating pump lasers and a single standing-wave cavity mode, two degenerate Zeeman sub-levels of the quantum gas are Raman coupled in a double-$\Lambda$-configuration. Beyond a critical pump strength the cavity mode is populated via coherent superradiant Raman scattering from the two pump lasers, leading to the appearance of a dynamical spin-orbit coupling for the atoms. We identify three quantum phases with distinct atomic and photonic properties: the normal ``homogeneous'' phase, the superradiant ``spin-helix'' phase, and the superradiant ``supersolid spin-density-wave'' phase. The latter exhibits an emergent periodic atomic density distribution with an orthorhombic centered rectangular-lattice structure due to the interplay between the coherent photon scattering into the resonator and the collision-induced momentum coupling. The transverse lattice spacing of the emergent crystal is set by the dynamic spin-orbit coupling.

The Ncoa7 locus regulates V-ATPase formation and function, neurodevelopment and behaviour

Members of the Tre2/Bub2/Cdc16 (TBC), lysin motif (LysM), domain catalytic (TLDc) protein family are associated with multiple neurodevelopmental disorders, although their exact roles in disease remain unclear. For example, nuclear receptor coactivator 7 (NCOA7) has been associated with autism, although almost nothing is known regarding the mode-of-action of this TLDc protein in the nervous system. Here we investigated the molecular function of NCOA7 in neurons and generated a novel mouse model to determine the consequences of deleting this locus in vivo. We show that NCOA7 interacts with the cytoplasmic domain of the vacuolar (V)-ATPase in the brain and demonstrate that this protein is required for normal assembly and activity of this critical proton pump. Neurons lacking Ncoa7 exhibit altered development alongside defective lysosomal formation and function; accordingly, Ncoa7 deletion animals exhibited abnormal neuronal patterning defects and a reduced expression of lysosomal markers. Furthermore, behavioural assessment revealed anxiety and social defects in mice lacking Ncoa7. In summary, we demonstrate that NCOA7 is an important V-ATPase regulatory protein in the brain, modulating lysosomal function, neuronal connectivity and behaviour; thus our study reveals a molecular mechanism controlling endolysosomal homeostasis that is essential for neurodevelopment.Graphic abstract

Математичне моделювання режимів запирання при кавітаційних автоколиваннях у гідравлічних системах з кавітуючими насосами РРД

As known from the study of cavity flows in fixed channels (Venturi tube), with decreasing channel outlet pressure there comes a point where the flow rate ceases to increase. To increase the flow rate, the inlet pressure must be increased. This phenomenon of flow rate limitation at a fixed inlet pressure is due to a critical regime of cavity flow at the narrowest cross-section and is termed choking. Impeller pumps also exhibit choking regimes described by the so-called chocking characteristic, which relates the critical pump flow rate to the inlet pressure. This work is aimed at extending a hydrodynamic model of cavitating pumps of liquid-propellant rocket engines (LPREs) by including a mathematical simulation of chocking regimes. A mechanism of realization of the chocking process in pumps is proposed. The mechanism is as follows. When the parameter oscillation amplitudes are high enough, the inlet flow rate and pressure computed at integration step i may be in the inadmissible range, i.e., below the chocking regime characteristic. In this case, the flow rate and the pressure must be refined. It is found that the computed decrease in the cavitation self-oscillation frequency in comparison with the eigenfrequency of a hydraulic system with a cavitating pump is close to its experimental value in the case where the inlet flow rate and pressure are assumed to be coordinates of the point of intersection of the choking characteristic and the line that connects the values of the pump inlet flow rate and pressure computed at integration steps i-1 and i. It is shown that the LPRE pump choking characteristic is a specific nonlinearity associated with the critical cavity flow in the pump and may manifest itself at high parameter oscillation amplitudes. It is found that the choking characteristic of an LPRE pump affects the cavitation oscillation parameters to a greater extent than the cavity volume vs. pump inlet pressure and flow rate relationship does and is the governing nonlinearity in the pump system in choking.

ANALISA PENYEBAB KERUSAKAN PADA IMPELLER POMPA SENTRIFUGAL DENGAN MENGGUNAKAN METODE FAILURE MODE EFFECTS ANALYSIS (FMEA) DI PT. MESKOM AGRO SARIMAS (IN PRESS)

Centrifugal pump is one type of dynamic pump, centrifugal pump is also one of the hydraulic fluid flow machines basically used to machines basically used to move incopessible fluid flow from one place to another. At PT. MESKOM AGRO SARIMAS, one of the production processes uses a centrifugal pump to supply canal water in the manufacture of mineral water. These centrifugal pumps often experience small or large damage specifically in the impeller. This study uses a failure mode effect analysis (FMEA) method to analyze the causes of damage to the pump used at PT. MESKOM AGRO SARIMAS . The FMEA method is a method used to analyze damage to components that might cause damage to centrifugal pumps. The results of the analysis found that the critical pump components based on the diagram are fishbone which has 5 failures with the highest value of Rpn. Keywords : FMEA, fishbone , impeller , centrifugal pump

Predicting RUL of Bearings in the Pumps of a Critical Industrial Air Treatment System

Predictive maintenance is emerging as a promising technique to overcome the limitations of periodic maintenance. It integrates automatic condition monitoring to evaluate the health status of a system or device, with the estimation of Remaining Useful Life (RUL) of its components, in order to schedule maintenance only when really needed, minimizing the downtime of a plant.
 In this paper, we report our results in evaluating the health conditions of the rotating ball bearings of a critical air pump which is part of the Clean Room industrial facility operating in the Micro-Technologies Laboratory of Fondazione Bruno Kessler. We instrumented such component with vibration and acoustic sensors with the aim of identifying a model of the evolving degradation and estimating the RUL of the bearings. The current dataset covers a period of one month before bearing replacement and about six months after the replacement. The first models, based on regression and particle filter processing of critical spectral components extracted from the sensors, indicate an estimated RUL of about 12 months that is in agreement with the average lifetime based on scheduled maintenance. Subsequent model evolutions have been observed in conjunction with scheduled greasing and periods of lower stress, which resulted in remarkable deviations from the initial degradation trends and in a consequent notable increase of the estimated RUL.
 Results achieved so far are promising and could be used to extend the temporal distance among periodic maintenance interventions according to the estimated RUL.

Non-Coulomb strong electron-hole binding in Ta2NiSe5 revealed by time- and angle-resolved photoemission spectroscopy

We reveal an ultrafast purely electronic phase transition in \TNS, which is a plausible excitonic insulator, after excited by an ultrafast infrared laser pulse. Specifically, the order parameter of the strong electron-hole binding shrinks with enhancing the pump pulse, and above a critical pump fluence, a photo-excited semimetallic state is experimentally identified with the absence of ultrafast structural transition. In addition, the bare valence and conduction bands and also the effective exciton binding energy in \TNS~are determined. These findings and detailed analysis suggest a bare nonequilibrium semimetallic phase in $Ta_2NiSe_5$ and the strong electron-hole binding cannot be exclusively driven by Coulomb interaction.

Cryo-EM Structures of a Gonococcal Multidrug Efflux Pump Illuminate a Mechanism of Drug Recognition and Resistance.

Neisseria gonorrhoeae is an obligate human pathogen and causative agent of the sexually transmitted infection (STI) gonorrhea. The most predominant and clinically important multidrug efflux system in N. gonorrhoeae is the multiple transferrable resistance (Mtr) pump, which mediates resistance to a number of different classes of structurally diverse antimicrobial agents, including clinically used antibiotics (e.g., β-lactams and macrolides), dyes, detergents and host-derived antimicrobials (e.g., cationic antimicrobial peptides and bile salts). Recently, it has been found that gonococci bearing mosaic-like sequences within the mtrD gene can result in amino acid changes that increase the MtrD multidrug efflux pump activity, probably by influencing antimicrobial recognition and/or extrusion to elevate the level of antibiotic resistance. Here, we report drug-bound solution structures of the MtrD multidrug efflux pump carrying a mosaic-like sequence using single-particle cryo-electron microscopy, with the antibiotics bound deeply inside the periplasmic domain of the pump. Through this structural approach coupled with genetic studies, we identify critical amino acids that are important for drug resistance and propose a mechanism for proton translocation.IMPORTANCENeisseria gonorrhoeae has become a highly antimicrobial-resistant Gram-negative pathogen. Multidrug efflux is a major mechanism that N. gonorrhoeae uses to counteract the action of multiple classes of antibiotics. It appears that gonococci bearing mosaic-like sequences within the gene mtrD, encoding the most predominant and clinically important transporter of any gonococcal multidrug efflux pump, significantly elevate drug resistance and enhance transport function. Here, we report cryo-electron microscopy (EM) structures of N. gonorrhoeae MtrD carrying a mosaic-like sequence that allow us to understand the mechanism of drug recognition. Our work will ultimately inform structure-guided drug design for inhibiting these critical multidrug efflux pumps.

ABCG2 transports anticancer drugs via a closed-to-open switch

ABCG2 is an ABC transporter that extrudes a variety of compounds from cells, and presents an obstacle in treating chemotherapy-resistant cancers. Despite recent structural insights, no anticancer drug bound to ABCG2 has been resolved, and the mechanisms of multidrug transport remain obscure. Such a gap of knowledge limits the development of novel compounds that block or evade this critical molecular pump. Here we present single-particle cryo-EM studies of ABCG2 in the apo state, and bound to the three structurally distinct chemotherapeutics. Without the binding of conformation-selective antibody fragments or inhibitors, the resting ABCG2 adopts a closed conformation. Our cryo-EM, biochemical, and functional analyses reveal the binding mode of three chemotherapeutic compounds, demonstrate how these molecules open the closed conformation of the transporter, and establish that imatinib is particularly effective in stabilizing the inward facing conformation of ABCG2. Together these studies reveal the previously unrecognized conformational cycle of ABCG2.