Pumping Effect Research Articles

Control of the Dynamic Regimes of a Superconducting Nanointerferometer

An analytical solution has been found to describe dynamic processes in a superconducting nanointerferometer with negligibly low inductances that is included in a high-Q factor resonator. The effect of nonlinearity in the system, as well as the effect of external parametric pumping, has been analyzed. The screening of detected dynamic modes in the studied nanostructure in the resonator is performed in a wide range and their positions on the plane of the parameters have been determined. A significant influence of phase effects on the evolution of the system has been demonstrated and phase relations allowing one to control the output signal intensity have been evaluated. The detected effects open new possibilities for developing and testing basic elements of modern quantum computing systems.

An Analysis of the Carreau Fluid Pumping According to the Saffman Slip Condition Using an Asymmetric Direction by Peristaltic Pumps

Hall Effect of the peristalsis pump on a Carreau fluid is analyzed in the Saffman slip boundary conditions at the walls. Asymmetric channel is taken into consideration by wave’s propagation on the channel walls. Long wavelength and low Raynold number assumption an asymmetric into consideration for obtaining the fluid flow solution. The perturbation method is applied for solving the constructed mathematical model and the results are obtained for various characteristics of the fluid. Different graphical representations and comparisons have been examined to discuss various developments of fluid characteristics parameters of interest individually.

Hydrocarbon accumulation characteristics in basement reservoirs and exploration targets of deep basement reservoirs in onshore China

Based on the global basement reservoir database and the dissection of basement reservoirs in China, the characteristics of hydrocarbon accumulation in basement reservoirs are analyzed, and the favorable conditions for hydrocarbon accumulation in deep basement reservoirs are investigated to highlight the exploration targets. The discovered basement reservoirs worldwide are mainly buried in the Archean and Precambrian granitic and metamorphic formations with depths less than 4 500 m, and the relatively large reservoirs have been found in rift, back-arc and foreland basins in tectonic active zones of the Meso-Cenozoic plates. The hydrocarbon accumulation in basement reservoirs exhibits the characteristics in three aspects. First, the porous-fractured reservoirs with low porosity and ultra-low permeability are dominant, where extensive hydrocarbon accumulation occurred during the weathering denudation and later tectonic reworking of the basin basement. High resistance to compaction allows the physical properties of these highly heterogeneous reservoirs to be independent of the buried depth. Second, the hydrocarbons were sourced from the formations outside the basement. The source-reservoir assemblages are divided into contacted source rock-basement and separated source rock-basement patterns. Third, the abnormal high pressure in the source rock and the normal–low pressure in the basement reservoirs cause a large pressure difference between the source rock and the reservoirs, which is conducive to the pumping effect of hydrocarbons in the deep basement. The deep basement prospects are mainly evaluated by the factors such as tectonic activity of basement, source-reservoir combination, development of large deep faults (especially strike-slip faults), and regional seals. The Precambrian crystalline basements at the margin of the intracontinental rifts in cratonic basins, as well as the Paleozoic folded basements and the Meso-Cenozoic fault-block basements adjacent to the hydrocarbon generation depressions, have favorable conditions for hydrocarbon accumulation, and thus they are considered as the main targets for future exploration of deep basement reservoirs.

Biomimetic Dual Absorption-Adsorption Networked MXene Aerogel-Pump for Integrated Water Harvesting and Power Generation System.

Harvesting atmospheric water and converting it into electricity play vital roles in advancing next-generation energy conversion systems. However, the current water harvester systems suffer from a weak water capture ability and poor recyclability due to high diffusion barriers and low sorption kinetics, which significantly limit their practical application. Herein, we drew inspiration from the natural "Pump effect" observed in wood and successfully developed a dual "absorption-adsorption" networked MXene aerogel atmospheric water harvester (MAWH) through ice templating and confining LiCl processes, thereby serving multiple purposes of clean water production, passive dehumidification, and power generation. The MAWH benefits from the dual H-bond network of MXene and cellulose nanocrystals (absorption network) and the hygroscopic properties of lithium chloride (adsorption network). Furthermore, its aligned wood-like channel structure efficiently eliminates water nucleation near the 3D network, resulting in fast moisture absorption. The developed MAWH demonstrates a high moisture absorption ability of 3.12 g g-1 at 90% relative humidity (RH), featuring rapid vapor transport rates and durable cyclic performance. When compared with commercial desiccants such as the 4A molecular sieve and silica gel, the MAWH can reduce the RH from 80% to 20% within just 6 h. Most notably, our integrated MAWH-based water harvesting-power generation system achieves a high voltage of ∼0.12 V at 77% RH, showcasing its potential for practical application. These developed MAWHs are considered as high-performance atmospheric water harvesters in the water collection and power generation field.

Understanding effects from overburden drilling of piles—a rational approach to reduce the impacts on the surroundings

This paper presents two case studies dealing with undesirable impacts of overburden drilling of casings for end-bearing piles to bedrock. Monitored pore-water pressures and ground settlements are used to document and assess the influence from rotary percussive drilling with “down-the-hole” (DTH) hammers. The studies show that drilling with high-pressure air-driven DTH hammers may cause considerable erosion and soil volume loss adjacent to the drill bit and along the casing, resulting in settlements of the surrounding ground. The risk of soil volume loss increases when the drilling is carried out in erodible soils such as silt and fine sands. The volume loss is found to be caused by a combined air-lift pump effect and a Venturi suction effect. Monitoring pore pressures in the vicinity of the drilling may be used to reduce soil volume loss and prevent damaging settlements. Results from drilling with water-driven DTH hammer showed significantly less ground settlements and influence on pore pressures compared to using an air-driven hammer. The study suggests that the drilling parameters flow rate and penetration rate, and the cross-sectional area of the pile casing can be combined in a non-dimensional methodology to assess the mass balance of drill cuttings when drilling with water flushing. A design framework is suggested to guide overburden drilling in urban settings to reduce potential impact on the surroundings.

Multi-Method Investigation of Blood Damage Induced By Blood Pumps in Different Clinical Support Modes.

To investigate the effects of blood pumps operated in different modes on nonphysiologic flow patterns, cell and protein function, and the risk of bleeding, thrombosis, and hemolysis, an extracorporeal blood pump (CentriMag) was operated in three clinical modalities including heart failure (HF), venous-venous (V-V) extracorporeal membrane oxygenation (ECMO), and venous-arterial (V-A) ECMO. Computational fluid dynamics (CFD) methods and coupled hemolysis models as well as recently developed bleeding and thrombosis models associated with changes in platelet and von Willebrand factor (vWF) function were used to predict hydraulic performance and hemocompatibility. The V-A ECMO mode had the highest flow losses and shear stress levels, the V-V ECMO mode was intermediate, and the HF mode was the lowest. Different nonphysiologic flow patterns altered cell/protein morphology and function. The V-A ECMO mode resulted in the highest levels of platelet activation, receptor shedding, vWF unfolding, and high molecular weight multimers vWF (HMWM-vWF) degradation, leading to the lowest platelet adhesion and the highest vWF binding capacity, intermediate in the V-V ECMO mode, and opposite in the HF mode. The V-A ECMO mode resulted in the highest risk of bleeding, thrombosis, and hemolysis, with the V-V ECMO mode intermediate and the HF mode lowest. These findings are supported by published experimental or clinical statistics. Further studies found that secondary blood flow passages resulted in the highest risk of blood damage. Nonphysiologic blood flow patterns were strongly associated with cell and protein function changing, blood damage, and complications.

Comparison of postoperative analgesia in children following ropivacaine and lidocaine surgical field infiltration with epinephrine for cleft palate repair: A double-blinded, randomized controlled trial

Study objectiveThe study aimed to evaluate the efficacy of ropivacaine in providing postoperative analgesia for children undergoing cleft palate repair. MethodsA double-blinded, randomized controlled trial was conducted on sixty-four children scheduled for cleft palate repair. The patients received either local infiltration with 1% lidocaine or 0.2% ropivacaine before incision. The primary outcome was the postoperative average pain score, and secondary outcomes included pain scores at various time points, consumption of flurbiprofen and hydromorphone, effectiveness of nurse-controlled analgesia pump, and incidence of bradycardia, vomiting, and respiratory depression. Main resultsThe results showed that the postoperative average pain score was significantly lower in the ropivacaine group compared to the lidocaine group (1.27±0.28 vs. 1.75±0.29, P<0.001). Pain scores at multiple postoperative time points were also lower in the ropivac:aine group. Additionally, consumption of flurbiprofen and hydromorphone was lower, and ineffective compressions of the nurse-controlled analgesia pump were reduced in the ropivacaine group. The incidence of vomiting, bradycardia, and respiratory depression did not show significant differences between the two groups. ConclusionLocal infiltration with ropivacaine effectively provided postoperative analgesia for children undergoing cleft palate repair without major side effects. It was found to be superior to lidocaine in reducing the need for additional rescue analgesia.

Impacts of pumping on the spatiotemporal dynamics of a fresh-saline water mixing zone in a coastal lagoon-aquifer system

Study regionThe Songjiho coastal lagoon, located in the Gangwon Province, Korea, has a unique geographic setting surrounded by mountains and the ocean. Its distinctive hydrological configuration consists of two smaller sub-lakes interconnected by a narrow channel. Its hydrodynamics is significantly influenced by an inlet and outlet, which are connected to the inflowing stream and tidal current, respectively. Study focusWe examined the effect of pumping on the spatiotemporal dynamics of the fresh-saline water mixing zone (FSM) to gain insights into the underlying response mechanisms by pumping. We conducted a series of systematic pumping tests at three fully screened wells installed in the lagoon-aquifer. We monitored electrical conductivity and water temperature with depth. Additionally, we collected and analyzed comprehensive sets of relevant hydrogeological field data. New hydrological insights for the regionOur investigation has pinpointed the dispersion resulting from the concentration gradient as a primary governing factor of the behavior of the FSM. Furthermore, the results also underscore the crucial relationship between the permeability of the layers and the mixing process, which is affected by the inherent heterogeneities in the geological structure and hydraulic properties of the aquifer. In light of these findings, we propose a conceptual model that comprehensively represents the spatiotemporal variations of the coastal lagoon-aquifer system. The model will serve as a valuable tool for understanding and predicting the complex interplay of factors that influence the behavior of this complex hydrogeological system.

A portable low-cost device to quantify advective gas fluxes from mofettes into the lower atmosphere: First application to Starzach mofettes (Germany)

In this study, we introduce a portable low-cost device for in situ gas emission measurement from focused point sources of CO2, such as mofettes. We assess the individual sensors’ precision with calibration experiments and perform an independent verification of the system’s ability to measure gas flow rates in the range of liters per second. The results from one week of continuous CO2 flow observation from a wet mofette at the Starzach site is presented and correlated with the ambient meteorological dynamics. In the observed period, the gas flow rate of the examined mofette exhibits a dominant cycle of around four seconds that is linked to the gas rising upwards through a water column. We find the examined mofette to have a daily emission of 465 kg ±16 %. Furthermore, two events were observed that increased the flow rate abruptly by around 25 % within only a few minutes and a decaying period of 24 hours. These types of events were previously observed by others at the same site but dismissed as measurement errors. We discuss these events as a hydrogeological phenomenon similar to cold-water geyser eruptions. For meteorological events like the passages of high pressure fronts with steep changes in atmospheric pressure, we do not see a significant correlation between atmospheric parameters and the rate of gas exhalation in our one-week time frame, suggesting that on short timescales the atmospheric pumping effect plays a minor role for wet mofettes at the Starzach site.

Performance analysis and optimization of a solar assisted heat pump-driven vacuum membrane distillation system for liquid desiccant regeneration

Liquid desiccant air-conditioning (LDAC) system is one of the excellent alternatives to conventional vapor compression refrigeration system due to its great energy-saving potential. However, regeneration of diluted liquid desiccant is the main energy-consuming process, and its performance plays a significant role in LDAC system. Recently vacuum membrane distillation (VMD) is becoming an emerging and promising separation process rely on the advantage of high permeate flux and low energy losses. The interest of usage solar energy techniques for feed solution heating in VMD systems is regarded as a sustainable path for membrane distillation process. In this work, a solar-driven VMD system incorporating a vapor-compression heat pump for liquid desiccant regeneration is introduced. An adapted solar/heat pump hybrid heating strategy has been devised to establish a connection between the heat-demanding process and the solar thermal supply. A comprehensive multicriteria assessment of energy, exergy, and environmental evaluation is conducted, and the influences of crucial parameters on both key components and system performance are evaluated to ensure a systematic examination. Results show that both the COP and STEC decrease obviously with the growth of the inlet solution temperature, whereas SEEC is improved abviously from 410.6 kW·h/m3 to 566.1 kW·h/m3 due to the effect of heat pump. The exergy analysis indicates that exergy losses in solar collector and stratified heat storage tank accounted for over 80 % of the total exergy losses. Additionally, single-objective optimization and multi-objective optimization are employed to explore the optimum operating conditions of key componets and whole system. Results show the ideal optimal solution can be obtained with a COP of 19.92 and a SEEC of 142.89 kW·h/m3 when the weights of COP and SEEC are taken as [0.5, 0.5].

The Effect of Long-Term Corrosion on a Molten Salt Pump in Contact With a Ternary Mixture in a CSP Plant

Solar thermal plants commonly plan their operation for a period of approximately 25 years. Therefore, it is key to accurately predict and evaluate the damage and faults occurring for that long period. Among all components, we find that choosing the heat storage medium (molten salt) and the material (steel) used in the equipment and pipping plays a crucial role in the plant’s design. We tested the long-term corrosion effect of the molten salt pump in a low-melting-point ternary mixture composed of 30wt.%LiNO3+57wt.%KNO3+13wt.%NaNO3 over a period of more than 5 years, corresponding to 30,000 hours of operation in a pilot experimental facility built at the University of Antofagasta (Chile).

TURNING REGION HEAT TRANSFER IN FIVE, STATIONARY AND ROTATING, MULTI-PASS CHANNELS WITH VARIOUS ASPECT RATIOS

Abstract This work summarizes studies that experimentally investigated the effect of rotation on heat transfer in the 180-deg tip and hub turns of cooling channels with various aspect ratios (ARs). The studied AR ranges from 1:4 to 4:1, which is the typical range within turbine blades. In addition to the smooth surface case, the cases with 45-deg angled ribs and turning vanes are also included. For several designs, the effect of channel orientation with respect to the angle of rotation is also investigated. This work covers a wide range of Reynolds and buoyancy numbers. The rib turbulators are found to have higher heat transfer enhancement and larger disturbance on the flow impingement on the tip and hub walls in channels with a wider aspect ratio. The rotational effect is reduced by the presence of ribs and turning vanes, and it is also reduced in the blade-shaped channels with the angled rotation feature. The tip wall heat transfer is increased by rotation due to the pumping effect from the centrifugal force; however, the hub wall heat transfer is reduced. The effect of rotation is most prominent in the first pass of the channels and is gradually mitigated in the following pass after the turns. This work provides stationary and rotational heat transfer coefficients in the tip and hub turning regions in blades, and heat transfer correlations for a variety of cooling channel designs can be generated, which is of benefit to the gas turbine community.

A numerical study on applying ion concentration polarization in micropump design

This work focuses on applying the phenomenon of ion concentration polarization to design and investigate a micropump model that is a kind of electroosmotic micropump. Numerical study is conducted for ion concentration polarization in the manner that generates electro-osmosis flow and pumping effect. The formation of the extended space charge layer and the actions of the electric field upon this layer is applied to generate electro-osmosis flow to drive flow in the system. It is clarified that pumping effect can be enhanced by improving the geometry configurations. Multiple simulations are conducted to obtain an optimal micropump design.

Effect of heat pump drying temperature on moisture migration characteristics and quality of instant Tremella fuciformis

Low-field nuclear magnetic resonance (LF-NMR) was used to analyze the moisture migration characteristics and water distribution of instant Tremella fuciformis (ITF) during heat pump drying at 35 °C, 45 °C and 55 °C. A fuzzy mathematical evaluation method was then used to investigate the effect of heat pump drying temperatures (35 °C, 45 °C and 55 °C) on the quality of ITF. Based on the screened appropriate temperature of 45 °C, the thin layer heat pump drying curve and drying rate curve of ITF were drawn, then four mathematical models were tested based on the coefficient of determination (R2). The result showed three water components (bound water (T21), immobilized water (T22), and free water (T23)) in ITF before drying. During the drying process, the heat pump drying of ITF was carried out gradually from the outer to the inner. The sensory total score (77.66 ± 6.57), rehydration ratio (4803.00 ± 90.00%), and viscosity (45.01 ± 3.61 Pa s) of ITF in heat pump drying at 45 °C were the best. The optimal drying temperature of 45 °C was obtained by the fuzzy comprehensive evaluation with the highest comprehensive score of 77.85%. With the prolongation of drying time, the water content of ITF showed a gradual decreasing trend, and the water content was controlled to below 8.51% after 6 h. The drying curve shows that the drying phase of the ITF is divided into three phases, including preheat, constant speed and deceleration. The drying speed first increases, remains constant in the middle and then decreases. Among the four models tested, the cubic regression equation aligned with the change rule of the ITF drying curve (R2 = 0.99397). By studying the effect of drying temperature on the moisture migration characteristics and the quality of ITF, we aim to provide more data support for the production of T. fuciformis.

A concise review of the effect of efflux pump on biofilm intensity in bacteria with a special view to Mycobacterium

Abstract Excessive, arbitrary, self-medication, and misuse of antibiotics have caused widespread antibiotic resistance, but with the emergence of multiple antibiotic resistances, these concerns have increased. Efflux pumps are an important pathway involved in antibiotic resistance and can send the drug used in clinical cases out of the bacterial cell. Many studies show the role of these pumps in biofilm formation as well as increasing biofilm formation. Considering the effective relationship between antibiotic resistance from the efflux pump pathway and biofilm increase in bacteria, the purpose of this study was to investigate various aspects of the efflux pump pathway in biofilm exacerbation, especially in Mycobacterium. For this purpose, we studied more than 60 articles with keywords efflux pump, antibiotic resistance, biofilm formation, and Mycobacterium tuberculosis from valuable data sources such as PubMed, Scopus, Google Scholar, and Web of Science. Through the investigation, we came to the conclusion that the efflux pump is one of the main pathways of antibiotic resistance in bacteria, especially M. tuberculosis, which can increase the formation of biofilm in them, and as a result of this cooperation, the treatment process can become much more difficult. We suggest that all drug resistance pathways and their genes are investigated in the occurrence of other diseases, not only tuberculosis, in different geographical areas.

Effects of combined vacuum and heat pump drying on drying characteristics and physicochemical properties of pineapple

Vacuum drying (VD) and heat pump drying (HPD) are widely used in the food industry. However, their application is limited due to low drying efficiency and the resultant poor quality of dried products. Additionally, varying drying durations in combined drying can markedly impact the physical and chemical properties as well as the nutritional content of the dried product. To achieve the highest quality dried products, VD + HPD was initially compared and identified as the most suitable drying method. This paper investigates the impact of the first stage drying duration on the physical characteristics (color, microstructure, texture, volume shrinkage rate (VSR), rehydration rate (RR)) and bioactive components (total phenolic content (TPC), total flavonoid content (TFC), Polysaccharides) of pineapple. The results indicated that VD + HPD necessitated lower energy consumption and markedly enhanced the physical properties of dried products. The brightness, rehydration rate (RR), color difference, volume shrinkage rate (VSR), and surface microstructure of pineapple dried by VD 5h + HPD 5.5h were all optimal. In comparison with other tested drying methods, the textural properties (hardness, chewiness, viscosity) and bioactive components (TPC, Polysaccharides) exhibited significant improvement. Overall, these results indicate that VD5h + HPD5.5h can be viewed as a valuable technology for improving the quality of dried pineapples.

A digital twin concept for optimizing the use of high-temperature heat pumps to reduce waste in industrial renewable energy systems

In light of the global industrial sector's steadfast pursuit of sustainable solutions to mitigate carbon emissions and efficiently minimize energy inefficiencies, the significance of novel approaches to energy optimization becomes increasingly evident. This research presents a novel digital twin concept that is designed to enhance the efficiency and effectiveness of high-temperature heat pumps in industrial renewable energy systems. Through the utilization of real-time data and complex computer modeling techniques, our proposed digital twin model seamlessly presents a comprehensive perspective on energy flows. This approach identifies inefficiencies and delivers practical insights to mitigate waste. The incorporation of this approach into pre-existing eco-conscious renewable energy systems has the potential to greatly enhance the effectiveness, predictability, and long-term viability of industrial processes. The empirical findings, obtained from multiple case studies conducted in industrial settings, provide evidence of the potential benefits in terms of energy waste reduction, and maximize the durability of systems. The results of our initial studies provide a foundation for the utilization of digital twin technologies in the field of industrial renewable energy systems optimization, representing a significant advancement towards a more environmentally sustainable industrial landscape.

Ultrastrong-coupled magnon–polariton in a dynamical inductor based on magnetic-insulator/topological-insulator bilayers

We theoretically study a magnon–polariton in a dynamical inductor consisting of a coil and a bilayer of ferromagnetic insulator (FI) with perpendicular magnetization and a three-dimensional topological insulator (TI). Taking into account the coherent magnetic-dipole (Zeeman) interaction as well as the dissipative spin pumping effect on the FI/TI interface, we formulate a dynamical permeability of the FI/TI bilayer and calculate a corresponding electric admittance of an RLC-circuit. As a result, the spin pumping gives rise to a competitive effect on the modes hybridization, whereas a huge level repulsion due to the coherent coupling, which reaches the ultrastrong coupling regime, is found at room temperature for realistic parameter sets. Our work may open a new avenue for designing on-chip microwave devices based on a magnon–polariton in the RLC-circuit.

Design and Analysis of a Cardioid Flow Tube Valveless Piezoelectric Pump for Medical Applications.

Piezoelectric pumps play an important role in modern medical technology. To improve the flow rate of valveless piezoelectric pumps with flow tube structures and promote the miniaturization and integration of their designs, a cardioid flow tube valveless piezoelectric pump (CFTVPP) is proposed in this study. The symmetric dual-bend tube design of CFTVPP holds great potential in applications such as fluid mixing and heat dissipation systems. The structure and working principle of the CFTVPP are analyzed, and flow resistance and velocity equations are established. Furthermore, the flow characteristics of the cardioid flow tube (CFT) are investigated through computational fluid dynamics, and the output performance of valveless piezoelectric pumps with different bend radii is studied. Experimental results demonstrate that CFTVPP exhibits the pumping effect, with a maximum vibration amplitude of 182.5 μm (at 22 Hz, 100 V) and a maximum output flow rate of 5.69 mL/min (at 25 Hz, 100 V). The results indicate that a smaller bend radius of the converging bend leads to a higher output flow rate, while the performance of valveless piezoelectric pumps with different diverging bends shows insignificant differences. The CFTVPP offers advantages such as a high output flow rate, low cost, small size for easy integration, and ease of manufacturing.

Influences of hydrodynamics on dissolved inorganic carbon in deep subtropical reservoir: Insights from hydrodynamic model and carbon isotope analysis

Dam construction significantly impacts river hydrodynamics, subsequently influencing carbon biogeochemical processes. However, the influence of hydrodynamic conditions on the migration and transformation of Dissolved Inorganic Carbon (DIC) remains uncertain. To bridge this knowledge gap, we integrated hydrochemistry, isotopic composition (δ13CDIC), and a hydrodynamic model (CE-QUAL-W2) to examine the distinctions, control mechanisms, and environmental effects of DIC biogeochemical processes in a typical large and deep reservoir (Hongjiadu Reservoir) under different hydrodynamic conditions. We evaluated hydrodynamic alterations through the Schmidt stability index and relative water column stability. The analysis disclosed that during weak hydrodynamics periods, the energy necessary for complete mixing the surface and deep water was 34 times higher (3615.32 J/m2 vs.106.86 J/m2), and stability was 13 times greater (312.96 vs. 24.69) compared to periods of strong hydrodynamics. Additionally, the spatiotemporal heterogeneity of DIC concentrations (1.4 % to -9.1 %) and δ13CDIC (-1.7 % to -19.5 %) from the dry to wet seasons reflected disparities in DIC control mechanisms under varied hydrodynamic conditions. Based on model simulations, our calculations indicate that during weak hydrodynamics periods, the enhancement of the biological carbon pump effect resulted in substantial sequestration of DIC, reaching up to 379.6 t-DIC·d−1 in the water. Conversely, during strong hydrodynamics periods, DIC retention capacity decreased by 69.2 t·d−1, resulting in reservoir CO2 emissions of 22.7 × 104 t, which were more than 7 times higher than during weak hydrodynamics periods (3.2 × 104 t). Our findings emphasize the discernible impact of hydrodynamic conditions on reservoir biogeochemical processes related to DIC. Considering the increasing construction of reservoirs globally, understanding and controlling hydrodynamic conditions are crucial for mitigating CO2 emissions and optimizing reservoir management.