Flow Rate Control Research Articles

Precision flow rate control during micro-scale material extrusion by iterative learning of pressure-flow rate relationships

Despite its low-cost and broad material capability, material extrusion-based additive manufacturing suffers from low process resolution and dimensional accuracy, due to challenges with precisely controlling the ink flow rate during the printing process, particularly while using small nozzles and complex inks. In this paper, we present a novel approach to control the ink flow rate by utilizing (1) a printhead capable of concurrently monitoring and controlling the printing pressure (P) and steady-state flow rate (Q) and (2) an automatic iterative learning approach to elucidate the flow rate-pressure relationships for the system in the form of a Q-P relator model. Our studies showed that flow rate accuracy within 10% can be achieved with nozzles as small as 100 microns in diameter through implementation of the trained Q-P relator with both pressure and piston velocity-controlled printing. Particularly, Q-P relator enables proper selection of printing pressure to achieve desired flow rate during pressure-controlled printing, while providing a means of smart-priming of the system prior to velocity controlled printing to overcome the system transients. We also characterized the performance of the iterative learning process, focusing on time to convergence, effect of steady-state detection, and accuracy variation across various time scales. Presented results indicate that the proposed method will increase the microscale material extrusion process resolution and accuracy, and minimize material waste and reduce time to production.

Qualitative and quantitative diagnosis of internal hydrogen leakage in fuel cell based on air flowrate control and open-circuit voltage measurements

Internal hydrogen leakage faults in fuel cells can cause severe performance loss and safety risks. The aim of this study is to achieve qualitative and quantitative diagnoses of internal leakage in fuel cell based on air flowrate control and transient voltage measurements. The hydrogen crossover characteristics of a fault-free and defective fuel cell are both investigated, and the effectiveness of the diagnosis method is evaluated by comparing and analyzing the results before and after the leakage fault introduction. The results suggest that hydrogen leakage failure inside fuel cell is dominated by convection processes. In airflow interruption tests, where the fuel cell is operated under open-circuit conditions with given anode overpressures, the fall time of the cell voltage is used as a qualitative measure of internal hydrogen leakage, and fault occurrence can be recognized by a considerable decrease in this indicator. Through cyclic staircase flowrate sweep tests, we obtain good estimates of internal leakage rates in the defective fuel cell. These diagnostic methods can be performed directly under hydrogen/air conditions, and there is no need for additional power source equipment dedicated to generating excitation signals for fuel cell, giving them great potential in on-board applications.

Development of icy regolith simulant for lunar permanently shadowed regions

The lunar poles are thought to contain vast ice deposits that could be beneficial to future space exploration efforts. However, it is not well characterized how water ice content affects regolith and dust physical properties. In order to develop suitable technologies that can operate safely in the cryogenic regolith, testing should be conducted in simulated regolith. We present a new production method for lunar permanently shadowed regions (PSRs) icy regolith simulant. We build on an existing lunar highlands simulant, by adapting it for lunar poles, where water ice might be present in PSRs. We have demonstrated a production concept using controllable simulant and water flow rates to make granular icy simulant with variable water ice content. We found that with this production method, icy simulant has a porosity of 0.6 to 0.7, that persists even after dehydration.

Synthesis of Bis(cyclic carbonates) from Epoxy Resin under Microwave Irradiation: The Structural Analysis and Evaluation of Thermal Properties.

This article describes the use of microwave irradiation in the synthesis of bis(cyclo carbonate) compounds (BCCs) in bulk (without solvent) from carbon dioxide capture using an epoxidized compound-a commercial epoxy resin-and compares this process to the conventional method. CO2 cycloaddition to epoxides is an ecological and efficient method for the formation of bis(cyclic carbonates). Moreover, the introduction of gas into the reaction mixture was carried out at atmospheric pressure with a controlled flow rate, which is advantageous from an economic point of view. Progressive structural changes and the presence of characteristic chemical groups were monitored using attenuated total reflectance infrared spectroscopy with Fourier transform. The obtained crude products were purified to obtain three fractions, which were subjected to detailed structural analysis using FT-IR and 13CNMR. The formation of the main product with two cyclic carbonates was confirmed. The presence of monomers, dimers and trimers in individual fractions as well as their thermal stability were determined, and the molecular masses in individual fractions were determined using gel permeation chromatography (GPC).

ESO-based robust adaptive control for dual closed-loop fuel control system in aeroengine

To improve the flowrate control accuracy of fuel control system at high supply pressure and large flowrate working condition, this paper proposes a novel dual closed-loop control for fuel metering unit (FMU) to address issues related to unknown velocity, matched/unmatched disturbances, and parameter uncertainties. Firstly, for a comprehensive assessment in flowrate feedback method, a global sensitive analysis is utilized to research the effect ratio of factors affecting the discharge flowrate. Then, a novel dual closed-loop control is proposed, in which the outer loop is flowrate loop, and a novel extended-state-observer (ESO)-based robust adaptive control without velocity sensor is used as the internal displacement loop control. Specifically, ESO can effectively estimate the unknown velocity and unmatched disturbance, and the parameter estimations can be updated by the adaptive law determined only by spool displacement and reference signal. The novel robust control can address matched/unmatched disturbances and model uncertainties effectively. Through Lyapunov method, it follows that the novel ESO-based robust adaptive control can achieve asymptotic tracking performance when occurring time-invariant disturbances and bounded tracking performance when occurring time-varying disturbances. Comparative experiments verify the superiority of the proposed control, which provides a new method and glimpse for the advanced control strategy of aeroengine.

Design and performance analysis of a heat pump system for motor phase change thermal storage

Along with the rapid economic development and social progress, the problem of energy and environment is becoming more and more outstanding. Therefore, it is very important to use new energy saving techniques to increase energy consumption and reduce energy consumption. In this paper, we have developed a hot water system, which is based on solar energy technology, gas-source heat pump, and phase change energy storage technology. The system was designed and constructed, and its performance was tested in various control conditions, with an emphasis on the analysis of the influence of phase change heat supply on heat storage properties. In this paper, the effect of the heat storage property is analyzed. Studies have shown that compared to a conventional tank that does not have a phase change heat storage device, the heat storage tanks equipped with phase change energy storage devices have longer discharge time, higher discharge temperature, better temperature, and better operation efficiency. In addition, the data show that flow rate control is also an important factor in optimizing the thermal storage characteristics of the system.

High-altitude long-duration latex balloon venting valves

With the demand of near-space exploration, it is required to continually improve the flat drifting capability of high-altitude latex balloons. To extend the flat drift time of latex balloons at a high altitude, it is necessary to design a gas release device to control the volume of gas discharged from the balloon. However, there are few such studies, especially on the type of high-altitude latex balloon exhaust valve and the control of release gas flow rate by balloon height. In this study, based on the high-altitude atmospheric data in Hunan Province, China, the release process of gas in high-altitude balloons in the fluid turbulence mode was determined using Reynolds method. The dynamic characteristics of two types of release valves, ball valve and butterfly valve, during the opening and closing and the steady-state flow characteristics of butterfly valve under a certain valve opening were simulated using gas motion equations and slip grid technology. By comparing the flow rate of these two types of valves at the same time, the adjustable time range under the same flow rate, as well as the ascending and drifting trajectory of the latex balloon, it was determined that the performance of butterfly valve is more suitable for the high-altitude latex balloon gas release system. Finally, the butterfly valve was applied to the high-altitude balloon gas release system, and a solution was designed for day and night flat drift balloons, which provide a reference for the design of high-altitude long-duration latex balloons.

Pneumatic Fault Monitoring and Control for Sustainable Compressed Air Systems

Sustainable development in the industrial sector has been widely explored in recent years, to achieve a carbon-neutral industry. Compressed air systems are widely used in the industrial sector. Numerous energy-saving improvements have been studied within this scope, as leaks make these systems inefficient. Nevertheless, it has yet to be seen how different optimisation techniques can be utilised to mitigate fault effects. This study shows how fault monitoring was performed on a multi-actuator system, using different time domain indicators including, mean and standard deviation. This was followed by exploring the system behaviour when pressure and flowrate control strategies were executed to minimize fault impacts. Fault monitoring, using the indicator data, was successful. For instance, as a 1 mm leak was induced and the consumption increased by 34%, the standard deviation in pressure drop reduced by 6% and the mean actuation time decreased by 13%. Though the mean in pressure drop was useful for fault monitoring other pressure indicators, including standard deviation, provided additional monitoring capabilities. During this monitoring exercise, it was also found that improved sensor accuracy resulted in less reading variations, obtaining more conclusive results and identifying faults of smaller sizes. As faults were accurately identified and characterised, it was then possible to mitigate their effects via pressure and flowrate adjustments. Results proved promising, as both contributed to air consumption decreases of 16% and 11%, respectively. Although such modifications decreased the production rate by 2-5%, the previously mentioned savings outweighed this decrease. This work highlights the need for development of fault monitoring and control systems which maintain the productivity and energy performance of pneumatic systems.

MRI Study of the Influence of the Catalytic Layer on the Interfacial Water Transfer in PEMFC Membrane-Electrode Assemblies

A better understanding of the limitations induced by decreasing platinum content in PEMFC membrane-electrode assemblies, both in terms of operation and aging of the electrodes and ionomer membrane is still needed. More specifically, more information and understanding of water transport across the membrane / electrode interface is required. Few experimental techniques can be used to measure the water interfacial resistance in these sandwiches as the method must be able to measure both the water flux through the assembly and the water content at the membrane interface. Among them, magnetic resonance imaging (MRI) can be effectively exploited by using surface coils to enhance the NMR signal and improve the quality of the measurement [1,2]. In the present study, MRI was used to distinguish the water diffusion resistance within thick Nafion-type PFSA membranes from the water transfer interfacial resistance. Measurement of the water profiles across the membrane allowed for accurate evaluation of the evolution of the diffusion coefficient as a function of water content. The determination of the water content at the interface and of the water flux through the membrane allowed the determination of the interface resistance for different hygrometry conditions imposed on both sides. The experiments were then repeated on membrane / electrode and electrode / membrane / electrode samples to evaluate the impact of the electrode layer. Our results show a strong evolution of the interfacial resistance as a function of the air humidity while the influence of the electrode does not seem to be preponderant. Figure (left): NMR experimental cell containing a Nafion N1110 sample fed by two streams of humid air with controlled flow rate and relative humidity (RH). (right): examples of water content () profiles measured by MRI (6 µm spatial resolution) in different RH conditions.

Study on the synergistic regulation strategy of load range and electrolysis efficiency of 250 kW alkaline electrolysis system under high-dynamic operation conditions

Alkaline water electrolysis (AWE) has the highest technological maturity among all the water electrolysis technologies for hydrogen production, however, reducing the minimum load boundary and improving the electrolysis efficiency are the technical challenges of the AWE system that still exist and urgently require optimization. The minimum load is primarily limited by the hydrogen to oxygen (HTO) from cross-diaphragm transfer and lye mixing, with HTO above 2.0% being a significant safety risk. Reducing the lye flow rate and pressure are effective while two of the few ways by regulating the operating parameters to improve the HTO thus extend the minimum load boundary, but will worsen electrolysis efficiency. Therefore, this study proposes a synergistic regulation strategy of pressure and lye flow rate: maximizing pressure and lye flow rate during high load period to ensure high electrolysis efficiency; adjusting lye flow rate and pressure during medium load period to ensure HTO≤2.0% and maximize the electrolysis efficiency; and reducing lye flow rate and pressure to a low level during the low load period to broaden the minimum load so as to improve overall efficiency of AWE system when loading with fluctuant green electric. This work elaborates the HTO routes, influencing factors and parameter optimization mechanism by building a system-level steady-state and dynamic gas purity model. The optimal combination curve of pressure and lye flow rate is obtained and its control effect on performance parameters, in terms of minimum load, system energy consumption, energy utilization, electrolysis efficiency and so on, is compared and verified in high dynamic wind and photovoltaic (PV) power scenarios. Finally, the optimal wind & PV power ratios are explored based on the optimal operation curve, which will provide a reference for the future large-scale development of hydrogen production scenarios direct-coupled with wind and PV power. The minimum load is extended from 42.0% in the lye flow rate alone control to 21.2% in the pressure alone control and finally to 15.6% in the lye flow rate and pressure synergistic control method. In the absence of electrical replenishment, wind and PV energy utilization efficiency can reach up to 98.3% and 95.6%, respectively.

Tunable, graded band-gap TiO2 thin film solar cell deposited by HIPIMS on flexible substrate

Among various types of thin-film solar cell (TFSC), the amorphous silicon type exhibits low and unstable conversion efficiency. Compound solar cells, on the other hand, are with a shortage of rare metals and toxic metals usage, not to mention unacceptable high deposition temperature. To overcome these problems and material cost consideration, the titanium-based oxide material known as potential photovoltaic material was chosen to develop a novel TFSC. During film deposition, the oxygen flow rate was adjusted to obtain p-TiO/n-TiO2 as the p-n junction, where p-TiO acts as the absorption layer and n-TiO2 as the window layer, whilst in an attempt in this study is to develop a graded bandgap n-TiO2 by progressive control of N2 flow rate to favor the electron-hole pairs separation and thus increased conversion efficiency. Meanwhile, a high-power impulse magnetron sputtering (HIPIMS) technique was used to conduct film deposition for providing high-density plasma that is beneficial for crystalline growth at low temperature. Ultimately, a flexible photovoltaic device composed of [PI/Ni (V)/ p-TiO/Graded bandgap n-TiO2/IZO/Al] is expected to be achieved.Experimental results show that the p-TiO absorption layer obtained at an oxygen/argon flow rate ratio of 0.28 exhibits a higher degree of crystallinity and enlarged grain size, leading to designated electrical properties. The carrier mobility and electrical resistivity are 2.18 cm2/Vs and 8.45 × 10−4 Ω-cm, respectively. The optical bandgap of the absorption layer p-TiO is about 2.27 eV. On the other hand, the n-TiO2 window layer slightly decreases its bandgap energy from 3.20 eV to 3.18 eV when the nitrogen flow rate increases from 0 to 50 sccm though, the increased external quantum efficiency (EQE) and the associated better conversion efficiency is found (in comparison with the intrinsic n-TiO2 window layer). It is undoubtedly contributed by the graded energy gap structure. Ultimately, the assembled photovoltaic device of [PI/Ni(V)/p-TiO/Graded bandgap n-TiO2/IZO/Al] presents an external quantum efficiency of 45 % under 310 nm monochromatic irradiation and photovoltaic efficiency of 0.2 %.

An embedded microfluidic valve for dynamic control of cellular communication.

The communication between different cell populations is an important aspect of many natural phenomena that can be studied with microfluidics. Using microfluidic valves, these complex interactions can be studied with a higher level of control by placing a valve between physically separated populations. However, most current valve designs do not display the properties necessary for this type of system, such as providing variable flow rate when embedded inside a microfluidic device. While some valves have been shown to have such tunable behavior, they have not been used for dynamic, real-time outputs. We present an electric solenoid valve that can be fabricated completely outside of a cleanroom and placed into any microfluidic device to offer control of dynamic fluid flow rates and profiles. After characterizing the behavior of this valve under controlled test conditions, we developed a regression model to determine the required input electrical signal to provide the solenoid the ability to create a desired flow profile. With this model, we demonstrated that the valve could be controlled to replicate a desired, time-varying pattern for the interface position of a co-laminar fluid stream. Our approach can be performed by other investigators with their microfluidic devices to produce predictable, dynamic fluidic behavior. In addition to modulating fluid flows, this work will be impactful for controlling cellular communication between distinct populations or even chemical reactions occurring in microfluidic channels.

Gravity-driven flow control in a fully integrated microfluidic cartridge for molecular point-of-care testing.

Molecular point-of-care testing (POCT) system is crucial for the timely prevention and control of infectious diseases. We recently proposed a gravity-driven microfluidic cartridge for molecular POCT detection, without the need for external sources or actuators, demonstrating the advantages in terms of the reduced cartridge size and low development costs. How to achieve precise control of liquid flow behavior is challenging for the gravity-driven cartridge. In this work, we explored the underlying mechanism of flow control in the cartridge and offered optimized solutions for our cartridge design to achieve precise control of dynamic flow rates and enhance pumping efficiency significantly. Through the computational fluid dynamics simulations, we demonstrated that adopting an asymptotic contraction chamber geometry design and a closed-loop air flow channel design with the cartridge inlet can facilitate stable laminar flow of the liquid in our microfluidic cartridge, enabling precise control of flow velocity. We further optimized the microchannel diameter and the contact angle of the liquid with the microchannel wall. The effectiveness of the optimized cartridge for POCT detection was well validated by the accurate detection of the human papillomavirus type 16 virus in the 120 clinical swab samples.

Exploring the Impacts of Exit Structures on Evacuation Efficiency

In the context of a fire emergency, safe and efficient exits are of paramount importance for pedestrian evacuation. The recent rapid development in the construction industry has rendered exit structures more diverse and complex. However, little attention has been paid to the influence of exit structures on the efficiency of crowd evacuation processes. In this paper, a tentative experiment was designed to preliminarily reveal the effects of five exit structures (Exit 1, Exit 2, Exit 4, Exit 5, and Exit 3 as examples for comparison) on crowd evacuation. Exit 1 has door leaves opening outward. Exit 2 has door leaves opening inward. Exit 3 has no leaves. Exit 4 consists of double-layer exit doors with the doors opening outward. Exit 5 comprises double-layer exit doors with the doors opening both sides outwards Subsequently, according to the properties of this experiment, a social force-based simulation model was established using the AnyLogic software 8.8.4. By changing the exit width and the crowd density, data such as evacuation time, flow rate, crowd density, and time delay were investigated in detail. The results revealed a notable variation in the evacuation efficiency depending on the deign of the exit. The respective flow rates for Exits 1, 2, 3, 4, and 5 were 0.66 people/(m·s), 0.77 people/(m·s), 0.80 people/(m·s), 0.71 people/(m·s), and 0.66 people/(m·s). Although Exit 3 excelled in terms of evacuation efficiency, it is not directly applicable to real architectural structures. Therefore, Exit 2 emerged as a highly promising solution in terms of flow rate and population control in the exit area, underscoring the effectiveness and practicality of its structural design. It is prospective that the results of this study can offer engineering and technical professionals valuable references and guidance concerning the design of exit structures.

Experimental investigation on acceleration of working fluid of heat pipe under bypass line operation

In a conventional heat pipe, the flow resistance is generated by the opposing flow of liquid and vapor across the phase-change interface. The flow resistance can impose a limitation on the heat transfer rate within the heat pipe, which can have an adverse effect on its overall efficiency. Therefore, reducing the flow resistance is essential for improving the heat transfer of heat pipe. The method of inducing a decrease in flow resistance is classified as an essential technology for improving the heat transfer performance of a heat pipe. In this study, experiments were conducted to induce operating fluid acceleration by decreasing the hydrodynamic resistance inside a heat pipe to improve thermal performance. A liquid bypass line connecting the three points of the condenser to the beginning of the evaporator was designed and installed, with four flow rate control valves attached to control the bypass flow rate at each bypass port. In this study, the working fluid acceleration was observed experimentally in bypass mode (all bypass valves opened) and normal mode (all bypass valves closed). According to the experimental results, the heat transfer efficiency of the heat pipe system improved by up to 106.5% in relation to the thermal resistance. The maximum thermal load in a horizontal position increased by up to 45.8% in the bypass mode.

Feasibility of Extracorporeal Delivery of Fusosomes to Generate CAR T Cells In Vivo

Fusosomes are viral vectors pseudotyped with modified paramyxovirus envelopes targeting specific cell types. A CD8-targeted fusosome delivering a CD19CAR transgene has the potential to provide an off-the-shelf therapeutic approach to generate in vivo CD19-directed chimeric antigen receptor (CAR) T cells in patients. For an in vivo gene delivery platform there are several approaches for administration that could be considered including direct intravenous (IV) administration or extracorporeal delivery (ECD). With ECD, patients would first undergo apheresis, then fusosomes would be retained with patient peripheral blood mononuclear cells (PBMCs) in the apheresis bag for a brief period of time before the entire contents of the bag is IV delivered into the same patient. Here, we demonstrate the feasibility of this approach to generate in vivo CAR T cells in a clinical setting with a mock infusion and discuss the translation of these findings to direct IV administration. A healthy donor was apheresed to collect PBMCs using standard apheresis equipment. No further cell enrichment, separation, or washing was performed. CD8-targeted fusosome formulated in an isotonic cryoprotective buffer was administered into the apheresis bag by gravity via an infusion set at a dose of ~0.5 IU/cell, gently mixed and retained for 30 min. The contents of the bag were mock infused into sample collection bags at a controlled flow rate using an infusion pump. Samples were collected before and after fusosome addition, after 30 min retention, and every 30 min during the mock infusion. Cell counts and viability were measured by complete blood count (CBC) and flow cytometry analyses. Fusosome binding to CD8 + T cells was measured by flow cytometry. Cytokines and complement components in supernatants were measured by ELISA or MSD. Residual fusosome in the supernatant was measured by ddPCR. Transduction of CD8 + T cells was measured by flow cytometry and vector copy number (VCN) analysis after PBMCs were washed, activated with CD3/CD28 beads, and cultured for 8 days. Early transcription events were measured by ddPCR using specific amplicons targeting different DNA species generated during reverse transcription. The CD8-targeted fusosome was successfully deliveredusing aseptic techniques to a freshly collected apheresis bag.PBMC viability stayed high (>%95) throughout the process. There were no major changes in white blood cell, platelet, or red blood cell levels as measured by CBC analysis. There were no changes in CD8 + T cell phenotype throughout the time course. Fusosome binding to CD8 + T cells was detected as early as fusosome addition to the apheresis bag (~5 min) and increased over the course of the process. Analysis of vector genomes in the supernatants indicated presence of unbound residual fusosome. Exposure of PBMC to fusosome did not induce cytokine secretion or complement activation throughout the process. Early events of transduction of cells could be detected by analysis of reverse transcription intermediates. Analysis of cultured cells via both flow cytometry and VCN analysis indicated generation of CD8 + CAR T cells upon short-term exposure to fusosome. In vivo delivery ofCD8-targeted fusosome encoding a CD19CAR transgene enables a novel CAR T cell approach. This study demonstrated that administration of fusosomes via ECD is operationally feasible in a clinical setting and scale as a novel method of administration to generate CD8 + CD19CAR T cells in vivo. ECD setup also served as an in vitro pharmacokinetic model for direct IV infusion. In scenarios where in vivo exposure is limited due to very rapid clearance (e.g. few minutes), ECD has the benefit of reducing the volume of distribution and bringing T cells and fusosomes in close proximity for efficient gene delivery. The findings of study suggest that with rapid binding of fusosomes to CD8 + T cell leading to early transcription events, and an in vivo half-life of more than 30 min, fusosome may generate CAR T cells successfully via direct IV administration.

Green corrosion inhibitor for mild steel extracted from soybean leaves

The use of green-soluble inhibitors in the corrosive medium as alternatives to traditional inhibitors has increased due to the toxicity of the commonly used substances. These novel substances are selected owing to their low cost, ease of application as well as maintenance, and low environmental risk. This work aims to evaluate ethanolic-water extracts from post-harvest soybean (Glycine max) by-products as corrosion inhibitors for mild steel in an aggressive medium of sodium chloride. Soybean extracts were obtained by percolation at a controlled flow rate and temperature. To evaluate the anticorrosive efficiency, polarization curves of AISI 1030 steel were carried out at 1 and 7 days of immersion with different concentrations of the soybean extract. Weight loss measurements were carried out alongside potentiodynamic measurements. The steel samples were analyzed by scanning electron microscopy. The soybean extracts obtained reduced the corrosion rate of the steel, showing an efficiency of 30% at day 1. The inhibition efficiency increased up to 80% after 7 days of incubation with 2000 ppm of the extract. A Langmuir adsorption model was fitted to weight loss measurements. Kads and ΔGads obtained from the model were characteristic of physisorption. The corrosion potential was shifted toward more negative values, classifying the ethanolic-water soybean extract as a cathodic inhibitor. The steel surface for the samples incubated with 2000 ppm of soybean extract was greatly improved showing significantly fewer agglomeration of corrosion products. Soybean leaves are a promising by-product useful to produce ethanolic-water extracts to be used as green corrosion inhibitors.

Effect of intermittent pneumatic compression on preventing deep vein thrombosis using microfluidic vein chip.

Background: Deep Vein Thrombosis (DVT) is a common disease, frequently afflicting the lower limb veins of bedridden patients. Intermittent Pneumatic Compression (IPC) is often employed as an effective solution for this problem. In our study, a random selection of 264 patients underwent IPC treatment for either one or 8hours daily. The rate of severe venous thrombosis was substantially reduced in the IPC-treated group compared to the control group. However, real-time monitoring of blood flow during IPC operation periods remains a challenge, leading to rare awareness of IPC working mechanism on thrombosis prevention. Methods: Here, microfluidic chip methodology is used to create an in vitro vein-mimicking platform integrating venous valves in a deformable channel. Whole blood of patients after knee surgery was perfused into the venous channel at a controlled flow rate obtained from patients with IPC treatment clinically. Results: According to the numerical simulations results, both of an increase in compressive pressure and a decrease in time interval of IPC device can accelarete blood flow rate and the shear stress within the vein. The vein chip experiments also reveal that the fibrin accumulation can be greatly lowered in IPC treated group, indicating less thrombosis formation in future. A time interval of 24 seconds and a maximum contraction pressure of 40mmHg were proved to be the most effective parameters for the IPC device adopted in our clinical trail. Conclusion: This vein chip presents a novel method for observing the functional mechanisms of IPC device for DVT prevention. It provides crucial data for further standardization and optimization of IPC devices in clinical usage.

Conversion of seaweed waste to biochar for the removal of heavy metal ions from aqueous solution: A sustainable method to address eutrophication problem in water bodies

The present study investigated the sustainable approach for wastewater treatment using waste algal blooms. The current study investigated the removal of toxic metals namely chromium (Cr), nickel (Ni), and zinc (Zn) from aqueous solutions in batch and column studies using biochar produced by the marine algae Ulva reticulata. SEM/EDX, FTIR, and XRD were used to examine the adsorbents' properties and stability. The removal efficiency of toxic metals in batch operations was investigated by varying the parameters, which included pH, biochar dose, initial metal ion concentration, and contact time. Similarly, in the column study, the removal efficiency of heavy metal ions was investigated by varying bed height, flow rate, and initial metal ion concentration. Response Surface Methodology (Central Composite Design (CCD)) was used to confirm the linearity between the observed and estimated values of the adsorption quantity. The packed bed column demonstrated successful removal rates of 90.38% for Cr, 91.23% for Ni, and 89.92% for Zn heavy metals from aqueous solutions, under a controlled environment. The breakthrough analysis also shows that the Thomas and Adams-Bohart models best fit the regression values, allowing prior breakthroughs in the packed bed column to be predicted. Desorption studies were conducted to understand sorption and elution during different regeneration cycles. Adding 0.3 N sulfuric acid over 40 min resulted in the highest desorption rate of the column and adsorbent used for all three metal ions.

New formulations and experimental validation of non-stationary convolutions for the fast simulation of time-variant flowrates in ground heat exchangers

Flowrate control can have a significant positive impact on the thermal performance and economic profitability of ground-source heat pump systems. Including dynamic advective processes in the design phase, however, remains a challenging task, as few computationally efficient modeling tools allow for their adequate and accurate representation. The present work addresses this issue by presenting new formulations of non-stationary convolutions, an efficient simulation algorithm that relies on the theory of linear time-variant systems for predicting the thermal response of a ground heat exchanger to both dynamic heat loads and flow rates. First, the new original formulations are presented, which include (1) a simple time-domain expression and (2) a fast frequency-domain expression. Then, the efficiency and validity of the new formulations are verified using experimental multi-flowrate thermal response tests involving dynamic circulation, pumping and bleed flow rates in closed-loop and standing column well ground heat exchangers. Results show that the new formulations can reproduce the outlet fluid temperature of both experimental test cases with good accuracy ( MAE = 0.06 ∘ C and 0.26 ∘ C , respectively). At last, the high efficiency of the new frequency-domain expression is demonstrated, with the computing times ( 0.04 s and 0.01 s ) being 100 and 8 times faster than the original formulation in both scenarios.