Adjustment Of Flow Rate Research Articles

Prevention of Encrustation on Ureteral Stents: Which Surface Parameters Provide Guidance for the Development of Novel Stent Materials?

Encrustations of ureteral stents are one of the biggest problems with urological implants. Crystalline biofilms can occur alone or in combination with bacterial biofilms. To identify which surface parameters provide guidance for the development of novel stent materials, we used an in vitro encrustation system. Synthetic urine with increasing pH to simulate an infection situation was pumped over the polymer samples with adjusted flow rates at 37 °C to mimic the native body urine flow. Chemical surface features (contact angle, surface charge), as well as encrustations were characterized. The encrustations on the materials were analyzed quantitatively (dry mass) and qualitatively using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The aim of this comparative study was to identify crucial surface parameters that might predict the quantity and type of mineral deposits in vitro and provide guidance for the development and screening of new polymer-based biomaterials for ureteral stent design. For the first time, we could identify that, within the range of our polymers, those materials with a slight hydrophilicity and a strong negative zeta potential (around −60 mV) were most favorable for use as ureteral stent materials, as the deposition of crystalline biofilms was minimized.

Degradation of sulphachloropyridazine sodium in column reactor packed with CoFe2O4−loaded quartz sand via peroxymonosulfate activation: Insights into the amorphous phase, efficiency, and mechanism

A simple, low-cost, and highly efficient process is required to produce free radicals from peroxides for degradation of organic pollutants. In this study, for the first time, CoFe2O4 was immobilized on quartz sand support (CoFe2O4-QS) and then packed into the continuous flow column reactor to activate peroxymonosulfate (PMS) for degradation of sulphachloropyridazine sodium (SCP) in water. CoFe2O4 was synthesized at low temperature (300 °C, CoFe2O4-QS-300) and exhibited an amorphous structure to facilitate more efficient electron transfer. The continuous flow column reactor worked efficiently at adjustable flow rates and within a wide pH range. Our results showed that over 90% of SCP with an initial concentration of 20 mg L−1 was degraded under the conditions of 10 g CoFe2O4-QS-300 (1.0% CoFe2O4 loading), 75 mg L−1 PMS and a retention time of 46.1 s. In comparison with batch reactor, the continuous flow reactor simplified the process of catalyst reuse and significantly reduced the amount of metal leaching, in addition to the similar performance for SCP removal. Both the sulfate and hydroxyl radicals were produced during PMS activation. Meanwhile, the synergistic catalytic effects between solid Co(II) and Fe(III) were investigated and the associated mechanism was proposed, i.e. the presence of Fe(III) guaranteed the formation of hydroxyl groups, and then the nearby Co(II) accepted the hydroxyl groups to form Co(II)–OH complexes, which played a critical role in the activation of PMS. Moreover, the intermediates of SCP degradation were identified and the possible degradation pathways were proposed. Taken all together, the continuous flow column reactor developed in this study represents an efficient, novel and cost effective method for the removal of organic contaminants in industrial wastewater.

Analysis of co-flowing immiscible liquid streams and their interfaces in a high-throughput solvent extraction chip

Liquid–liquid flow profiles are central to the operation of microfluidic devices in a range of applications. We recently demonstrated a multi-stream solvent extraction (SX) chip that combines high-surface-to-volume ratios and volumetric throughput. Here, we study these flow profiles in detail using numerical simulations, with consideration of different boundary conditions. The two liquids differ in viscosity, modelled on platinum (aqueous) and extractant (organic) phases, and the position of the liquid–liquid interfaces (and therefore surface/volume and phase ratios) can be controlled by adjustment of flow rates. The prediction of the position of the interface requires the solution of the governing equations of fluid mechanics. The volume of fluid (VOF) method was used to simulate the dynamics of the organic and aqueous phases to reveal stable flow profiles. This experimentally validated computational model with the root-mean-square deviation of about 11 µm will be useful for simulation of microfluidic SX design and operation, particularly where process intensification is sought through scale-out.

Controlling inclusion evolution behavior by adjusting flow rate of shielding gas during direct energy deposition of AISI 316 L

To reveal the mechanism of oxidation and the effect of inclusion characteristics on the mechanical properties of additively-manufactured metal matrix, two groups of AISI 316 L stainless steel samples were fabricated under different flow rates of shielding gas (Ar) at two intensities of laser beam. As flow rates of shielding gas increased from 5 L/min to 25 L/min, the oxygen content in the melt pool decreased from 775 ppm to 375 ppm at low intensity of laser beam (73 W/m2), and from 677 ppm to 1470 ppm at high intensity of laser beam (725 W/m2). Variation in oxygen content affected melt pool shape, solidification texture, and the mechanical properties of the material. In each intensity of laser beam group, optimal flow rates of shielding gas condition for tensile property existed. As inclusion number density increased from 8866/mm2 to 45909/mm2, yield stress increased to 26 %. A rapid drop in ductility occurred at flow rate 5 L/min, because independently-nucleated spinel accelerated inclusion coalescence in the melt pool.

Steady-State Model of Pressure-Flow Characteristics Modulated by Occluders in Cardiopulmonary Bypass Systems

Cardiopulmonary bypass is a complex procedure that involves the maintenance of heart and lung functions using an external system during cardiac surgery. It is prone to significant human errors, which are mainly caused by inappropriate occluder operation that controls the perfusion balance by adjusting flow rates. Hence, there is a requirement for automatic occluder control; however, the relationship between occluder operation and flow rates remains unclear. The aim of this study is to use a steady-state model to evaluate the influence of occluder control on the flow and pressure of a cardiopulmonary bypass system. Perfusion experiments were performed using Newtonian (glycerin solution) and non-Newtonian (erythrocyte turbid solution) fluids to investigate the pressure-flow characteristics modulated by the occluder. We also visualized the fluid to verify the validity of the measurement data. Based on these experimental data, an exponential occlusion-pressure model is derived to express the relationships between the opening ratio of the occluder and flow rate. Estimation is then achieved by combining the occlusion-pressure model with the linear pressure-flow model. Results reveal that the combined model fitted the perfusion experiment data well for the venous and arterial line side ( $R^{2} = 0.946$ and 0.985, respectively; $p ). Further, leave-one-out cross-validation and Bland–Altman analysis confirmed that the combined model could predict flow rates accurately with minimal proportional and bias errors. Therefore, the proposed model can serve as a basis for the further development of cardiopulmonary manipulation systems.

Scalability of Sterilizing-Grade Filters in Different Filtration Modes.

Scalability of filter throughput in normal flow filtration runs is an important consideration in the development of biopharmaceutical downstream processes. Depending on the filtration mode used, filter device geometry can significantly affect scalability. In this study, scaling of different polyethersulfone sterilizing-grade filters was performed in two filtration modes-at constant flow and at constant pressure-using a particulate model solution as well as a cell-free mAb solution as a representative example. Both filtration methods were compared regarding their practicability as well as their scalability of the final filter throughput and the filtration time. The pressure-dependent filter fouling that occurred with the mAb solution and the model solution showed that using different pressures for small- and process-scale filtration runs could potentially influence the predicted filter capacity. Overall, good scalability of the final filter throughput was determined for filters ranging from small-scale flat disc filters (4.5 cm2) to large pleated filter assemblies (5.4 m2) in filtration runs at constant flow as well as for filter capsules (0.6 m2) of up to 10" for filtration runs at constant pressure. Moreover, at constant flow, the filtration time could be accurately predicted because it was determined by the adjusted flow rate. However, at constant pressure, potential resistances in process-scale devices can result in lower fluid fluxes and, hence, a longer unpredictable filtration time compared with small-scale filter elements. This paper introduces a novel scaling method performed at constant pressure that compensates for the pressure losses resulting from process-scale device resistances. Improved scalability regarding final filter throughput and filtration time are shown here with this scaling method compared with scaling at constant pressure. Therefore, this study provides information essential in decision-making to achieve optimal scaling within biopharmaceutical process development.

Enhancement of Machining Accuracy Utilizing Varied Cooling Oil Volume for Machine Tool Spindle

In this study, varied cooling oil volume (VOV) control was developed for the oil coolant of a machine tool. This allows adjustment of the oil circulation flow rate in terms of the machining loads and rotational speeds of the spindle to remove the generated heat effectively from the spindle. A mathematical model of the cooling oil flow rate in terms of the rotating speed and torque of the spindle for VOV method is developed. From the thermal deformation experiments with the VOV method, the thermal deformations in both the Y-axis and Z-axis can be greatly reduced, by 70.1 % and 73.5 %, respectively, in variable rotational speed operation with a short operational period (10 minutes). Moreover, the VOV method was applied to shorten the required warm-up time of the spindle. The required warm-up time of the spindle can be shortened by 50 %, while the three axes of the spindle attain stable thermal conditions. In practical machining experiments, the machining accuracy with the VOV method can be greatly enhanced by 34 % to 62 % in comparison with the current case of constant cooling oil volume (COV). The VOV control system in the machine tool spindle can effectively reduce the thermal deformation and shorten the required warm-up time. In addition, the machining accuracy can be greatly enhanced.

Autarkic desorption electrospray ionization source for on-site analysis of consumer goods.

A general-purpose desorption electrospray ionization (DESI) source is presented which is not bound to the laboratory site. It allows autarkic operation for a few hours and can be connected to different types of (autarkic or non-autarkic) mass spectrometers via an atmospheric-pressure interface. Technical characteristics are described as well as results from direct surface analysis of consumer goods such as plastics, fruit peels or pills, or from living objects such as human skin, demonstrating the detection of various target compounds such as plasticizers, pesticides, drugs or sun blockers. Quantitative analysis is demonstrated for phthalates in plastics. The geometry of the sample, the sample table and the sprayer were modified and characterized for optimization of the method. The autarkic ion source has a total size of 48.4 × 27.0 × 18.0 cm (l×w×h) and a total mass of 7 kg. The source delivers 5.5 bar pressurized air and an adjustable solvent flow rate down to 1.5 μl min-1 for the DESI sprayer. A rechargeable 25.6 V battery allows autarkic runtimes of more than 3.5 hours. Source optimization and characterization was done on an orbital trapping mass spectrometer. Connected to a portable mass spectrometer, the developed device makes DESI suitable for on-site analyses in e.g. consumer protection, border control or homeland security.

Microwave-Assisted Pyrolysis of Fuel Oil for Hydrocarbons Upgrading

By-product upgrading is crucial in hydrocarbon processing industries as it can increase the competitiveness of the business. This research investigated opportunity to upgrade fuel oil by-product obtained from olefins production by using microwave pyrolysis. A lab-scale quartz reactor filled with placed inside a 1,200 watts household microwave oven was used for the experiments. Coconut-based activated carbon was used as a microwave receptor. Microwave powers were varied at 600 W, 840 W and 1,200 W to adjust cracking temperature between 800°C and 900°C. The effect of residence time was investigated by adjusting flow rate of N2 carrier gas. The chemical compositions and product yields were analyzed by using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). It was revealed that hydrogen, carbon monoxide, carbon dioxide and hydrocarbon gaseous product (alkanes, naphthenics and alkenes) were produced as the main products. For liquid products, the main compositions were cycloalkenes and polycyclic aromatic groups.

Programmable hydraulic resistor for microfluidic chips using electrogate arrays

Flow rates play an important role in microfluidic devices because they affect the transport of chemicals and determine where and when (bio)chemical reactions occur in these devices. Flow rates can conveniently be determined using external peripherals in active microfluidics. However, setting specific flow rates in passive microfluidics is a significant challenge because they are encoded on a design and fabrication level, leaving little freedom to users for adjusting flow rates for specific applications. Here, we present a programmable hydraulic resistor where an array of “electrogates” routes an incoming liquid through a set of resistors to modulate flow rates in microfluidic chips post-fabrication. This approach combines a battery-powered peripheral device with passive capillary-driven microfluidic chips for advanced flow rate control and measurement. We specifically show a programmable hydraulic resistor composed of 7 parallel resistors and 14 electrogates. A peripheral and smartphone application allow a user to activate selected electrogates and resistors, providing 127 (27-1) flow resistance combinations with values spanning on a 500 fold range. The electrogates feature a capillary pinning site (i.e. trench across the flow path) to stop a solution and an electrode, which can be activated in a few ms using a 3 V bias to resume flow based on electrowetting. The hydraulic resistor and microfluidic chip shown here enable flow rates from ~0.09 nL.s−1 up to ~5.66 nL.s−1 with the resistor occupying a footprint of only 15.8 mm2 on a 1 × 2 cm2 microfluidic chip fabricated in silicon. We illustrate how a programmable hydraulic resistor can be used to set flow rate conditions for laminar co-flow of 2 liquids and the enzymatic conversion of a substrate by stationary enzymes (alkaline phosphatase) downstream of the programmable hydraulic resistor.

Optimal Control of a PDE Model of an Invasive Species in a River

Managing invasive species in rivers can be assisted by appropriate adjustment of flow rates. Using a partial differential equation (PDE) model representing an invasive population in a river, we investigate controlling the water discharge rate as a management strategy. Our goal is to see how controlling the water discharge rate will affect the invasive population, and more specifically how water discharges may force the invasive population downstream. We complete the analysis of a flow control problem, which seeks to minimize the invasive population upstream while minimizing the cost of this management. Using an optimality system, consisting of our population PDE, an adjoint PDE, and corresponding optimal control characterization, we illustrate some numerical simulations in which parameters are varied to determine how far upstream the invasive population reaches. We also change the river’s cross-sectional area to investigate its impact on the optimal control.

Battery-free, lightweight, injectable microsystem for in vivo wireless pharmacology and optogenetics

Pharmacology and optogenetics are widely used in neuroscience research to study the central and peripheral nervous systems. While both approaches allow for sophisticated studies of neural circuitry, continued advances are, in part, hampered by technology limitations associated with requirements for physical tethers that connect external equipment to rigid probes inserted into delicate regions of the brain. The results can lead to tissue damage and alterations in behavioral tasks and natural movements, with additional difficulties in use for studies that involve social interactions and/or motions in complex 3-dimensional environments. These disadvantages are particularly pronounced in research that demands combined optogenetic and pharmacological functions in a single experiment. Here, we present a lightweight, wireless, battery-free injectable microsystem that combines soft microfluidic and microscale inorganic light-emitting diode probes for programmable pharmacology and optogenetics, designed to offer the features of drug refillability and adjustable flow rates, together with programmable control over the temporal profiles. The technology has potential for large-scale manufacturing and broad distribution to the neuroscience community, with capabilities in targeting specific neuronal populations in freely moving animals. In addition, the same platform can easily be adapted for a wide range of other types of passive or active electronic functions, including electrical stimulation.

Gasification of wet microalgae to produce H2-rich syngas and electricity: A thermodynamic study considering exergy analysis

In this work, a novel integrated gasification system was developed for wet microalgae to produce hydrogen-rich syngas and electricity. The proposed system consists of six major stages: (i) in-situ drying of wet microalgae, (ii) pyrolysis of dried microalgae, (iii) conversion of tar (produced in the pyrolysis stage), (iv) gasification of pyrolysis products, (v) combustion of biochar producing electricity, and (vi) post-treatment of syngas to remove CO2. The proposed gasification was modeled by thermodynamic simulation using Aspen Plus®. The developed thermodynamic model was first validated against experimental data concerning product composition and yields of the pyrolysis stage under the same operating conditions. Then, performance of the developed system was evaluated for gasification of Porphyra under various operating parameters, including moisture contents, gasifying agent (O2/steam) flow rates, and biochar distributions between gasification and combustion units. Syngas quality, cold gas efficiency (CGE), and overall energy and exergy efficiencies were considered as the performance metrics. Finally, it was found that under certain operating conditions, moisture content is beneficial to syngas composition, while adverse trends are found for CGE, and overall energy and exergy efficiencies. A proper adjustment of O2 flow rate can improve both syngas composition and energy performance.

Viscous fluid dissipation system model acting on the active principle

There are solutions in terms of seismic isolation and energy dissipation that are successfully applied all over the world to building structures but also to high-way and rail infrastructure elements represented by bridges and viaducts. These structures must remain functional even after they have been requested by a considerable magnitude earthquake. This is why research activities aiming the development and modernization of these mechanical systems, which play a decisive role in ensuring the optimal stability of these structures, are justified. Fluid dissipation systems were originally developed as passive protection systems but over time they have been constructively improved with intelligent control systems that have the potential to considerably increase the efficiency of these systems by making use direct control over the amount of energy which can be dissipated through these protection systems. Such a dissipative viscous fluid system is described in this paper as a more evolved constructive system than the passive principle model. Active control over the operation of this device is materialized by altering the working fluid flow rates through the constructional elements of the dissipation device assembly. This flow rate adjustment is made by means of a flow controller present within the control unit. The mathematical model characterizing the functioning of an active viscous fluid dissipation system is presented, as well as a numerical analysis describing the function of such a dissipative system depending on the additional mass of the isolated structure to which the protective device is attached. The numerical analysis is based on a set of specific values presented in the paper. These dissipation systems are primarily used in bridge or viaduct structures, being responsible for limiting the relative displacements between the structural elements where they are mounted. This method provides greater security through the rigid connection achieved between the structural frames acting as anchorages. Entry into action is made in the occurrence of a seismic event when the piston displacement is recorded and by changing the momentarily flow rate values of the circulating fluid the amount of energy dissipated is adjusted by means of the viscous fluid device. There are presented the advantages and disadvantages related to the use of such seismic energy dissipative systems attached to the construction structures.

Modeling of Wet Antenna Attenuation for Precipitation Estimation From Microwave Links

This letter presents an analysis of wet antenna attenuation (WAA) from an electrodynamic perspective. The WAA is a relevant part of the path attenuation determined from the received signal level (RSL). In the case of extracting rain rates from path attenuation, as it is done with data from country-wide commercial microwave link (CML) networks, the WAA is a significant error source and leads to overestimation of rainfall. To handle this effect, a model, based on the three antenna parameters, reflectivity, efficiency, and directivity, is developed. The model allows the variation of those three parameters depending on the degree of wetness and shows that WAA is composed of variations of antenna impedance, antenna efficiency, and antenna directivity. The suitability of the theoretical model was assessed by a full-wave numerical simulation of a pyramidal horn antenna at 18 GHz with homogeneous water film on the surface of the antenna cover. The result of this simulation is a quantification of these three subeffects. For verification of the simulation, an antenna, similar to the antenna in the simulation, was manufactured and a controlled sprinkler device to generate a water film was built. The adjustable water flow rate determines the thickness of the water film. The parameters were generated by measuring the near field and the reflectivity of the antenna in an anechoic chamber, with a near-field scanning system and a vector network analyzer, under different flow rates equaling different water film thicknesses. From these results, the reflectivity, directivity, and efficiency were computed and compared with the results of the full-wave simulation. It is found that the reflectivity is linked to water film thickness in a such way that the WAA can be deduced from monitoring the antenna reflectivity.

Stacked autoencoder for operation prediction of coke dry quenching process

Coke dry quenching (CDQ) is widely adopted for waste heat recovery in iron and steel plants. In this work, an economic benefit index was introduced to evaluate the performance of the CDQ system and stacked autoencoder (SAE) based deep neural networks are adopted for CDQ operation prediction. Based on the prediction results, a guidance is provided for online adjustment of the supplementary air flow rate, hence the efficiency and safety of the CDQ system can be improved. The case study on a real plant shows that the proposed method increases the economic efficiency of the CDQ process by 4.39%.

Adaptive load balancing based on accurate congestion feedback for asymmetric topologies

Datacenter load balancing schemes exist to facilitate parallel data transmission with multiple paths under various uncertainties such as traffic dynamics and topology asymmetries. Taking deployment challenges into account, several optimized schemes (e.g. CLOVE, Hermes) to ECMP balance load at end hosts. However, inaccurate congestion feedback exists in these solutions. They either detect congestion through Explicit Congestion Notification (ECN) and coarse-grained Round-Trip Time (RTT) measurements or are congestion-oblivious. These congestion feedbacks are not sufficient enough to indicate the accurate congestion status under asymmetry. And when rerouting events occur, outdated ACKs carrying congestion feedback of other paths can improperly influence the current sending rate. After our observations and analyses, these inaccurate congestion feedback can degrade performance.Therefore, we explore how to address above problems while ensuring good adaptation to existing switch hardware and network protocol stack. We propose ALB, an adaptive load balancing mechanism based on accurate congestion feedback running at end hosts, which is resilient to asymmetry. ALB leverages a latency-based congestion detection to precisely reroute new flowlets to the paths with lighter load, and an ACK correction method to avoid inaccurate flow rate adjustment. In large-scale simulations, ALB achieves up to 13% and 48% better average flow completion time (FCT) than CONGA and CLOVE-ECN under asymmetry, respectively. And compared with other schemes ALB improves the average and the 99th percentile FCTs for small flows under high bursty traffic by 43–174% and 75–129%. Under the situation of dynamic network changes, ALB also provides competitive overall performance and maintains stable performance for small flows.

Electrocoagulation using perforated electrodes: An increase in metalworking fluid removal from wastewater

A continuous electrocoagulation reactor with electrode polarity switch was used for removal of a metalworking fluid from synthetic oily water. The effects of perforating the aluminum electrodes, changing the number of holes, flow rate and the distance between electrodes were studied. Higher values of flow rate reduced final pH. Perforating the electrodes led to faster convergence of pH to its maximum value with no measurable increase in mass loss. If the distance between electrodes is also increased, there is an improvement in efficiency. With 10 holes, adjusting flow rate and inter-electrode distance, 90.2 ± 0.3% oil removal was achieved with a final pH of 8.83, which is within limits allowed by legislation.

Retrofit of a steam power plant using the adaptive neuro-fuzzy inference system in response to the load variation

Artificial neuro-fuzzy inference system known as the ANFIS tool was earlier developed by authors [1] for exergoeconomic optimization of an energy system. It was shown that the ANFIS could achieve the optimal solutions of systems with reasonable accuracy, very low computation time, and less dependency on experts’ knowledge. This paper aims to test a similar methodology for retrofit and real-time optimization of a large energy system in response to the load variation. A 250 MW unit in a fossil-fueled steam power plant was considered as a case study. The profit of the power plant was estimated using an exergoeconomic analysis, and it was maximized by adjusting flow rates of extracted steams that flow from turbines into feed-water heaters. The ANFIS methodology was developed in detail to optimize the profit of the proposed power plant. The advantage of the ANFIS for this purpose was compared to other alternatives such as genetic algorithm (GA) and fuzzy-inference system (FIS). It was shown that the ANFIS is much faster than the GA and considerably easier than the FIS for real-time optimization energy systems. It was shown that using ANFIS, it is possible to achieve more profit in the proposed power plant up to 320 $.hr−1 by implication control on the flow of extracted steam; however, this figure is different at various loads of the power plant.

A data mining-based method for revealing occupant behavior patterns in using mechanical ventilation systems of Dutch dwellings

Occupant behaviors influence the energy consumption of dwelling mechanical ventilation systems significantly. There is still a lack of effective method to analyze the occupant behaviors in adjusting the mechanical ventilation systems in buildings. Therefore, this study proposes a data mining-based method to reveal the occupant behavior patterns and the motivations behind. A first derivative Gaussian filter-based approach is developed to detect when an occupant increases or decreases the mechanical ventilation flowrate without direct measurements. A logistic regression-based statistical analysis approach is developed to find the crucial factors influencing the behaviors of increasing and decreasing ventilation flowrate. A K-means clustering-based analysis approach is introduced to further find the motivations behind the behaviors. The proposed data mining-based method discovers the ventilation behaviors and the crucial factors influencing them successfully for the occupants from the 10 dwellings located in a Dutch community. The motivation patterns of the ventilation flowrate adjustment behaviors are further revealed based on the discovered crucial factors. The discovered insights are useful to provide more accurate assumptions and inputs for the mechanical ventilation system models. It is also helpful to generate tailored design, refurbishment and control strategies.