Hold-up Time Research Articles

Improving Energy Density of Supercapacitors to Increase Hold-Up Time for Frequency Regulation in Power Grids

Improving Energy Density of Supercapacitors to Increase Hold-Up Time for Frequency Regulation in Power Grids

Modulating conductive filaments via thermally stable bilayer organic memristor

The basic unit of information in conductive bridge random access memory based on the redox mechanism of metal ions is physically stored in a conductive filament (CF). Therefore, the overall performance of the device is indissolubly related to the properties of such CFs, as unreliable performance often originates from unstable CFs behavior. However, accurately controlling the dissolution of CFs during device operation can be challenging due to their non-uniformity. This paper proposes a type of memristor based on a solid polymer electrolyte with a polyvinylpyrrolidone/polyvinyl alcohol composite layer structure. The properties of the composite layer are employed to regulate the number of CFs and the growth/fracture location, while the damage to the device by Joule heat is prevented. The device exhibits low operating voltage (0.5 V), stable switching conditions (2000 cycles), and a long holdup time (>3 × 104 s).

Boost DC-DC converter with regenerative snubber

To accommodate the wide range of input voltages supplied by redundant batteries and ensure an adequate hold-up time for communication systems during utility power failures, power supplies used in 5 G base stations typically include a front-end boost converter as the first stage and a second-stage isolated converter. In this paper, a new topology for a regenerative snubber in boost converters is proposed. Compared to traditional active or passive snubber topologies, the proposed snubber offers the advantages of having fewer components and occupying less space. Moreover, it does not require additional active devices and can be driven by widely-used commercial PWM control integrated circuits, achieving a higher level of cost-effectiveness and offering increased industrial applications. The final prototype of a power supply for a networking switch hub (as used in 5 G base stations) is fabricated to demonstrate the feasibility of the proposed method.

Manufacturing process transfer to a 30 kg/h continuous direct compression line with real-time composition monitoring

Transferring an existing marketed pharmaceutical product from batch to continuous manufacturing (CM) without changes in regulatory registration is a challenging task in the pharmaceutical industry. Continuous manufacturing can provide an increased production rate and better equipment utilisation while retaining key quality attributes of the final product. Continuous manufacturing necessitates the monitoring of critical quality attributes in real time by appropriate process analytical tools such as near infra-red (NIR) probes. The present work reports a successful transfer of an existing drug product from batch to continuous manufacturing process without changing the formulation. A key step was continuous powder blending, whose design and operating parameters including weir type, agitation rate, dynamic hold-up and residence time were systematically investigated with respect to process repeatability. A NIR-based multivariate data model for in-line composition monitoring has been developed and validated against an existing quality control method for measuring tablet content uniformity. A continuous manufacturing long-run with a throughput of 30 kg/h (approx. 128,000 tablets per hour), uninterrupted for 320 min, has been performed to test and validate the multivariate data model as well as the batch to continuous process transfer. The final disintegration and dissolution properties of tablets manufactured by the continuous process were found to be equivalent to those manufactured by the original batch process.

Design and management of photovoltaic energy in uninterruptible power supplies

The growing demand for sustainable systems due to climate change has led to increased reliance on renewable energy sources. However, this transition has raised concerns about power quality in power systems due to climate variations and the intermittent nature of renewables, photovoltaic energy generation in particular. In this context, uninterruptible power supply systems play a crucial role in ensuring reliable and high-quality energy supply. As an added benefit, photovoltaic energy generation may be integrated into uninterruptible power supply systems by sharing the inverter already present and storing generated energy in the batteries. In this paper, it is presented the design and management of photovoltaic energy, integrated into double-conversion uninterruptible power supplies. A method for selecting the suitable number of panels to be used in series in a given application is developed, considering the panel model used, and the environmental mission profile. A management algorithm for tracking the maximum power point of the photovoltaic generation while ensuring the hold-up time is proposed, introducing the dynamic hold-up time concept. Using the point for maximum power instead of the dynamic hold-up time at two different locations leads to voltage sags of 12.6% in the first and 24.3% in the second. Using the method to select the number of panels in series, 13 panels are selected for the first location, resulting in an annual generation that is only 2.3% smaller than the maximum power point. The results are validated using a hardware-in-the-loop platform and the dSpace Microlabbox 1202.

A Hybrid Phase-Frequency Control of Dual Active Bridge Converters for Hold-Up Time Extension in More Electric Aircrafts Applications

A Hybrid Phase-Frequency Control of Dual Active Bridge Converters for Hold-Up Time Extension in More Electric Aircrafts Applications

BART: A transferable liquid chromatography retention time library for bile acids

Identification of unknown bile acids, especially the distinguishment between isomers, requires retention times of a large number of reference standards, which are often not commercially available. Meanwhile, published retention information cannot be directly transferred across labs due to the differences between liquid chromatography (LC) systems, such as different extra column volume and dwell volume. To improve this situation, a transferrable retention time library for bile acids named BART was developed. BART was composed of isocratic retention models of 272 bile acids and a software tool to predict their gradient retention times on various LC systems. The isocratic retention times of bile acids were acquired on a Waters BEH C18 column with mobile phases of acidic ammonium acetate buffer and acetonitrile, and fit to the quadratic solvent strength model (QSSM). Segmented linear gradient retention times were calculated with holdup time (t0), dwell time (tD) and actual gradient profile corrected using 21 bile acid calibration standards. In addition to the reference system where the isocratic retention times were acquired, this approach has been validated on four other LC-MS systems in four labs with two gradient methods. Average root mean square errors (RMSE) between predicted and experimental retention times were 0.052 and 0.054 min for the two gradients tested, which were 9-fold more accurate than referring to a static retention time library. The library is freely available at https://bafinder.github.io/.

Змочування та контактна взаємодія напівпровідникових оксидних матеріалів Ga2O3, In2O3, ZnO з металічними розплавами у вакуумі

Semiconductor oxide materials such as gallium, indium and zinc oxides play an important role in a development and production of a variety of electronic devices. Experimental studies of these materials allow to define, for example energetic or other physical parameters of the devices created and also to improve existing technologies of their production, metallization and joining of electrocontacts by way of brazing which require additional wetting studies. It should be noted that data on wetting of mentioned oxides by metals are practically absent in literature. Thus a detailed experimental study of the interfacial interaction, adhesion and wetting of Ga2O3, In2O3 and ZnO oxide materials with some pure metal melts (Ga, In, Sn, Au,Ge, Ag, Cu) in vacuum was performed by the sessile drop method using photo- and video- fixing including temporal and temperature dependencies of contact angles. It was found that pure metals don't wet powdery pressed specimens of Ga and In oxides in the temperature range studied and vary in a rather narrow range. For ZnO system the significant effect of experiment temperature and hold-up time on the values of contact angles for some metals (Ga, Ge, Sn, Cu) is observed. For example wetting angles for Ga change from above 90 degrees at low temperatures up to 49 and full spreading at 1173⎯1373 K. This effect may be attributed to the activation of chemical reactions, change of oxide stabilities at high temperatures at the interface. Last metals can be used as adhesive-active additions to base brazing alloy. Keywords: gallium, indium, zinc oxides, semiconductor, wetting, contact interaction, metal melt.

A modelling workflow for quantification of photobioreactor performance

In this work we have developed a comprehensive modelling workflow for the quantification of photobioreactor performance. Computational Fluid Dynamics (CFD) modelling combined with Lagrangian particle tracking was used to characterise the flow field inside the reactor; this information was combined with a Monte-Carlo model of light attenuation and a kinetic growth model to predict the performance of the system over the duration of the entire batch. The CFD model was validated against measurements of the overall hold-up, local hold-up and mixing time for superficial velocities between 0.6 and 6 cm s−1 in a pilot-scale bubble column photobioreactor, with the CFD predictions agreeing with the experimental data. Comparison was also made between the predicted biomass concentration and experimental measurements using the diatom Phaeodactylum tricornutum, with the model predictions being in good agreement with the experimental results. The model was used to investigate a range of operating conditions and reactor designs, with the most promising predicted to give a 40 % increase in the biomass productivity. Results from this work can be used for the in-silico design and optimisation of photobioreactor systems, thereby enabling their wider use as a sustainable production technology.

Experiment and Numerical Study on the Dynamic Response of Foam Sandwich Panels under the Near-Field Blast Loading

Aiming at the problem that the blast load, generated by the explosion of the tandem-shaped-charge warhead, may cause damage to the warhead structure, material failure and even phase change, the material damage and structural protective capacity of the near-field blast load on the sandwich structure with foam-aluminum core were investigated by experimental test and numerical simulation. Firstly, the near-field blast test was performed to observe the deformation of sandwich structure and to collect the acceleration signals of fuze. Then, the mechanical properties of foam materials were tested, and a numerical model of blast load environment was established in the explicit dynamics software ANSYS/LS–DYNA 2020 R2. Finally, the experimental test data and simulation results were compared and analyzed. The strong agreement between the experiment and the simulation results indicates that the calculation method and simulation model are reasonable. Furthermore, the damage mode of foam-aluminum core materials with different densities and cell diameters under near-field blast load were carefully analyzed by simulation method. The simulation results show that, with the decrease of the density of foam-aluminum material and the increase of the cell chamber diameter, the deformation of the foam-aluminum panel gradually increases; the acceleration peak value of the fuze gradually decreases, and the pulse width barely changes and remains basically constant; the start and end times of the peak stress of the fuze cover gradually lag behind, and the peak stress hold-up time increases gradually; the maximum displacement deformation of the fuze cover decreases firstly and then increases. This work is expected to provide basic data and design guidelines for the graded foam sandwich panels of the blasting warhead fuze against the near-field blast load.

Current Limitations for Predicting Liquid Dispersion in Continuous Flow Bubble Columns Using CFD

Liquid-phase dispersion in a continuous flow bubble column was studied using computational fluid dynamics (CFD) and different combinations of turbulence and biphasic models. The results were compared with the experimental data obtained by the stimulus-response method in an air-water pilot-scale bubble column (2 m tall, 0.234 m internal diameter). Two flow combinations were examined: high flow rates of 3.2 m3 h−1 and 4.5 m3 h−1 and low flow rates of 1.98 m3 h−1 and 0.954 m3 h−1 for water and air, respectively. The objective was to evaluate commercial CFD 16.1 software to predict flow behavior beyond macroscale parameters such as hold-up or mixing time. The turbulence models that best replicated the experimental tracer dispersion were large eddy simulation-type models: scale-adaptive simulation (SAS) and shear stress transport-SAS. The simulations qualitatively predicted the tracer concentration with time but were unable to reveal the small-scale perturbations in the biphasic system. The predicted tracer residence time was double or triple the measured times for low and high flow, respectively.

Numerical investigation of the particle flow behaviors in a fluidized-bed drum by CFD-DEM

The fluidized-bed drum technology involving the combination of a fluidized bed and a rotating drum is used for the granulation and coating of particles, which has been successfully applied in industry. Nevertheless, there should be few published fundamental studies for exploring the particle flow behaviors in a fluidized-bed drum, particularly in the particle level. Consequently, the particle-scale DEM (Discrete Element Method) was coupled with CFD (Computational Fluid Dynamics) in this work to simulate the particle-fluid flow system in a fluidized-bed drum. The experiments in a small horizontal fluidized-bed drum were also carried out to validate the accuracy of our CFD-DEM model. Subsequently, the particle flows in a large inclined fluidized-bed drum were simulated by CFD-DEM, and the relatively comprehensive investigation for the influences of operational conditions (including the gas inlet velocity, drum rotation speed, drum inclination angle and fluidized-bed inclination angle) on the particle flow behaviors (e.g., the particle holdup, particle velocity and particle residence time) was carried out. According to the simulation results, the particle flow behaviors would be significantly affected by these operational conditions. However, increasing the gas inlet velocity could weaken the effects of drum rotation speed, drum inclination angle and fluidized-bed inclination angle.

Development of a gas chromatography system coupled to a metal-oxide semiconductor (MOS) sensor, with compensation of the temperature effects on the column for the measurement of ethene

Abstract. A possible way to reduce the size and complexity of common gas chromatography (GC) systems is the economization of the column temperature regulation system. To this end, a temperature compensation method was developed and validated on a benchtop GC-PDD (pulsed discharge detector) with ethene. An in-house-developed algorithm correlates the retention index of a test gas to the retention index of a previously selected reference gas. To investigate further methods of cost reduction, commercial gas sensors were tested as cheap, sensitive, and versatile detectors. Therefore, CO2 was chosen as a naturally occurring reference gas, while ethene was chosen as a maturity marker for climacteric fruits and hence as a test gas. A demonstrator, consisting of a simple syringe injection system, a PLOT (porous layer open tubular) column boxed in a polystyrene-foam housing, a commercial MOS (metal-oxide semiconductor) sensor for the test gas, and a CO2-specific IR (infrared) sensor, was used to set up a simple GC system and to apply this method on test measurements. Sorption parameters for ethene and CO2 were determined via a van 't Hoff plot, where the entropy S was −11.982 J mol−1 K−1 ΔSEthene0 and 1.351 J mol−1 K−1 ΔSCarbondioxide0, and the enthalpy H was −20.622 kJ mol−1 ΔHEthene0 and −14.792 kJ mol−1 ΔHCarbondioxide0, respectively. Ethene (100 ppm) measurements revealed a system-specific correction term of 0.652 min. Further measurements of ethene and interfering gases revealed a mean retention time for ethene of 3.093 min; the mean predicted retention time is 3.099 min. The demonstrator was able to identify the test gas, ethene, as a function of the reference gas, CO2, in a first approach, without a column heating system and in a gas mixture by applying a temperature compensation algorithm and a system-specific holdup time correction term.

Capuchin Search Particle Swarm Optimization (CS-PSO) based Optimized Approach to Improve the QoS Provisioning in Cloud Computing Environment

This review introduces the methods for further enhancing resource assignment in distributed computing situations taking into account QoS restrictions. While resource distribution typically affects the quality of service (QoS) of cloud organizations, QoS constraints such as response time, throughput, hold-up time, and makespan are key factors to take into account. The approach makes use of a methodology from the Capuchin Search Particle Large Number Improvement (CS-PSO) apparatus to smooth out resource designation while taking QoS constraints into account. Throughput, reaction time, makespan, holding time, and resource use are just a few of the objectives the approach works on. The method divides the resources in an optimum way using the K-medoids batching scheme. During batching, projects are divided into two-pack assembles, and the resource segment method is enhanced to obtain the optimal configuration. The exploratory association makes use of the JAVA device and the GWA-T-12 Bitbrains dataset for replication. The outrageous worth advancement problem of the multivariable capacity is addressed using the superior calculation. The simulation findings demonstrate that the core (Cloud Molecule Multitude Improvement, CPSO) computation during 500 ages has not reached assembly repeatedly, repeatedly, repeatedly, and repeatedly, respectively.The connection analysis reveals that the developed model outperforms the state-of-the-art approaches. Generally speaking, this approach provides significant areas of strength for a successful procedure for improving resource designation in distributed processing conditions and can be applied to address a variety of resource segment challenges, such as virtual machine setup, work arranging, and resource allocation. Because of this, the capuchin search molecule enhancement algorithm (CSPSO) ensures the success of the improvement measures, such as minimal streamlined polynomial math, rapid consolidation speed, high productivity, and a wide variety of people.

A Boost Converter with Lossless Passive Snubber for Powering the 5G Small Cell Station

The existing DC-DC quarter-brick or eighth-brick converter with a rated power of 300W is usually designed with a narrow input voltage range from 36 to 72 V DC with limited hold-up time. In this paper, a two-stage power supply unit constructed by a front-end boost converter cascaded with a brick converter is adopted to extend the input voltage range and the hold-up time. A new lossless snubber is proposed and applied to the boost converter to slow the slope of the drain-source voltage rising when the MOSFET is turned off. The experimental results show that the proposed snubber provides a boost converter with a higher conversion efficiency and less electromagnetic interference emissions.

A transient flow reactor for rapid gas switching at atmospheric pressure.

Herein, we present a design for a transient flow reactor system with high detection sensitivity and minimal dead volume, such that it is capable of sub-second switching of the gas stream flowing through a catalytic bed. We demonstrate the reactor's capabilities for step transient, pulse, and stream oscillation experiments using the model system of CO oxidation over Pd catalysts, and we find that we are able to precisely model step transients for CO oxidation using a pseudo-homogenous-packed bed reactor model. The design principles leading to minimal gas hold-up time and increased sensitivity that are described in this paper can be implemented into existing flow reactor designs with minimal cost, providing a readily accessible alternative to the existing transient instrumentation.

Evaluation of Hold-Up Volume Determination Methods and Markers in Hydrophilic Interaction Liquid Chromatography.

Common methods for hold-up time and volume determination in Reversed-Phase Liquid Chromatography (RPLC) have been tested for Hydrophilic Interaction Liquid Chromatography (HILIC). A zwitterionic ZIC-HILIC column has been used for the testing. The pycnometric determination method, based on differences in column weight when filled with water or organic solvent, provides the overall volume of solvent inside the column. This includes the volume of eluent semi-sorbed on the packing of the column, which acts as the main stationary phase. The homologous series approach, based on the retention behavior of homologues in relation to their molecular volume, allows the determination of accurate hold-up volumes. However, the application of this method is time-consuming. In some cases, large neutral markers with poor dipolarity/polarizability and hydrogen bonding interactions can be used as hold-up volume markers. This is the case of dodecylbenzene and nonadecane-2-one in clearly HILIC behaving chromatographic systems, the use of decanophenone as a marker can be even extended to the boundary between HILIC and RPLC. The elution volume of the marker remains nearly unaffected by the concentration of ammonium acetate in the mobile phase up to 20 mM. The injection of pure solvents to produce minor base-line disturbance as hold-up markers is strongly discouraged, since solvent peaks are complex to interpret and depend on the ionic strength of the eluent.

DC-Link Capacitance Reduction in PFC Rectifiers Employing PI+Notch Voltage Controllers

It is well-known that adding a notch filter in series with the typically employed type-II (or PI) regulator allows improving the tradeoff between dc-link voltage dynamics and grid-side current total harmonic distortion (THD) in practical single-phase power factor correction rectifiers. The article demonstrates that notch filter utilization alternatively allows reducing the value of dc-link capacitance in case hold-up time requirement is absent. The revealed value of minimum capacitance is expressed by explicit function of possible mains frequency values range, maximum expected grid voltage magnitude, rated system power, dc-link voltage set point, maximum tolerable grid-side current THD, and the desired phase margin (PM) of dc-link voltage loop. It is demonstrated that the proposed approach yields fourfold reduction of dc-link capacitance for typical values of 5% tolerable grid-side current THD under 40° PM constraint. Experimental results exhibit close-fitting resemblance to corresponding analytical predictions, verifying the proposed methodology.

Simulation of liquid flow in structured packings using CFD-methods

In this work the liquid flow in structured packings was investigated using the volume-of-fluid (VoF) method. Along with the fluid dynamics, convective transport of a tracer was studied to determine the residence time. A novel approach for the consideration of surface microstructure and perforations was applied and validated using data obtained with high-resolution computer tomography. Gas-liquid interfacial area, holdup and residence time distributions were well reproduced. The model was then applied to investigate two liquid systems (water and a mixture of water and triethyleneglycol), while two types of the standard packing Sulzer MellapakTM were explored. This allowed to evaluate the effects of liquid properties and geometric packing area on the flow.

Prediction of intensity of dispersion in surfactant solutions in vertical sparged bubble column

AbstractDispersion of liquid in bubble column is an important process in chemical and allied industries. In the present work, the dispersion characteristics of liquid phase in a bubble column is studied in three different surfactant solutions. A comparative analysis on the dispersion characteristics of liquid phase in different surfactants has been carried out. The gas holdup and mixing time are also analysed. The effect of different physiochemical properties and operating variables on the dispersion coefficient and gas holdup is examined. A novel model for the estimation of dispersion due to bubble motion has been developed which incorporates the effect of gas holdup, liquid viscosity and circulation velocity. The contribution of dispersion coefficient due to the bubble motion in overall dispersion is also examined. The value of velocity distribution parameter in three different surfactant solutions is also compared. Generalised correlations for gas holdup, dispersion coefficient and mixing time are also developed based on the physicochemical properties of liquid. This research may be useful for the selection and application of these three surfactants in industries. This article will also help researchers for designing multiphase flow system where role of dispersion due to the motion of bubbles is significant.